2,314 results
Search Results
2. Positronium in condensed matter studied with spin-polarized positrons
- Author
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Major, János, Seeger, Alfred, Ehmann, Jörg, Gessmann, Thomas, Araki, H., editor, Beig, R., editor, Ehlers, J., editor, Frisch, U., editor, Hepp, K., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Lehr, Sabine, editor, Jungmann, Klaus Peter, editor, Kowalski, Joachim, editor, Reinhard, Irene, editor, and Träger, Frank, editor
- Published
- 1997
- Full Text
- View/download PDF
3. Magnetic field enabled spin-state reconfiguration for highly sensitive paper-based photoelectrochemical bioanalysis.
- Author
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Tan, Xiaoran, Liang, Jiaxin, Yu, Haihan, Chen, Yuanyuan, Shan, Li, Ge, Shenguang, Zhang, Lina, Li, Li, and Yu, Jinghua
- Subjects
- *
MAGNETIC fields , *ELECTRON spin , *POLARIZED electrons , *PRECIPITATION (Chemistry) , *SPIN polarization , *ELECTRON spin states - Abstract
• The external magnetic field dramatically improved the analysis sensitivity of paper-based PEC biochip. • Electron spin polarization boosted photoinduced charge separation in sulfur-defected CdIn 2 S 4 /FeOOH and ferromagnetic ZnFe 2 O 4. • The ferromagnetic ZnFe 2 O 4 nanosphere was utilized as a multiple signal amplifier with strong quenching effects. • Enzymatic catalytic precipitation reaction was introduced for ultrasensitive detection of chlorpyrifos in real samples. Efficient carrier separation plays an utterly pivotal role in enhancing the sensitivity of photoelectrochemical (PEC) analysis. Here we report a concise yet powerful strategy of electron spin polarization induced by magnetic stimulation, to effectively modulate the efficiency of charge separation in a paper-based PEC (μ-PEC) sensing system. The electronic configuration of the sulfur-defected CdIn 2 S 4 /FeOOH photoactive matrix and ferromagnetic ZnFe 2 O 4 signal label were regulated via the electron parallel alignment along with spin state flip and reconstruction at particular active sites under external magnetic field, significantly facilitating the separation of photoinduced carriers. As a proof-of-concept application, the magnetic-triggerable spin-state reconfiguration coupled with enzymatic catalytic precipitation reaction was developed for detection of chlorpyrifos with a wide linear range of 10-2.5-106 ng mL−1 and low detection limit of 0.67 pg mL−1. This work provides the basis for understanding the role of magnetic stimulus in tailoring charge separation and constructing a universal strategy for high performance μ-PEC bioanalysis. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
4. Measuring random spin fluctuations for perturbation-free probes of spin dynamics and magnetic resonance (Invited Paper)
- Author
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Alexander V. Balatsky, Dwight G. Rickel, Darryl L. Smith, and Scott A. Crooker
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Magnonics ,Physics ,Spin polarization ,Condensed matter physics ,Spin wave ,Spin echo ,Spin Hall effect ,Condensed Matter::Strongly Correlated Electrons ,Ferromagnetic resonance ,Hyperfine structure ,Doublet state - Abstract
Random spin fluctuations in an equilibrium ensemble of paramagnetic spins are shown to contain valuable information about the system itself. We use off-resonant Faraday rotation to passively and sensitively "listen" to the random magnetization fluctuations (spin noise) in atomic alkali vapors. These random fluctuations generate spontaneous spin coherences which precess and decay with the same characteristic energy and time scales as the macroscopic magnetization of an intentionally polarized or driven ensemble. Correlation spectra of the measured spin noise reveals g-factors, nuclear spin, isotope abundance ratios, hyperfine splittings, nuclear moments, and spin coherence lifetimes -- without having to excite, optically pump, or otherwise drive the spin system away from thermal equilibrium. These noise signatures scale inversely with interaction volume, suggesting routes towards non-perturbative, sourceless magnetic resonance of small solid state spin systems.
- Published
- 2005
5. Magnetization dynamics driven by spin momentum transfer (Invited Paper)
- Author
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Y. Yang, Thomas McLendon Crawford, N. J. Gokemeijer, Mark William Covington, and Michael Allen Seigler
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Physics ,Condensed Matter::Materials Science ,Magnetization ,Magnetization dynamics ,Condensed matter physics ,Magnetoresistance ,Spin polarization ,Condensed Matter::Strongly Correlated Electrons ,Giant magnetoresistance ,Magnetization transfer ,Orbital magnetization ,Ferromagnetic resonance - Abstract
A spin-polarized dc current can induce steady-state, microwave frequency magnetization dynamics in a nanoscale ferromagnet. The torque that drives these dynamics originates from the exchange of spin angular momentum between conduction electrons and the magnetization. We present measurements of current perpendicular to the plane (CPP) giant magnetoresistance (GMR) nanopillar devices in which this phenomenon occurs. We focus on devices that contain one reference ferromagnetic layer that has a fixed magnetization and one free ferromagnetic layer with a magnetization that responds to spin torque. The resulting spin transfer induced magnetization dynamics combined with GMR lead to resistance noise, which we measure in both the frequency- and time-domain. The appearance of these dynamical states is consistent with spin transfer in that dynamics are observed only for those combinations of current direction and magnetic configuration in which spin torque opposes the FL configuration set by the magnetic field. Furthermore, the amplitude of the resultant resistance noise increases rapidly with increasing current until saturating at a value that is a large fraction of the magnetoresistance between parallel and antiparallel states. This behaviour is contrasted with similar measurements of a current-in-plane (CIP) GMR device in which the magnetic resistance noise is thermally activated.
- Published
- 2005
6. Femtosecond study of interplay between excitons, trions, and carriers in (Cd,Mn)Te quantum wells (Invited Paper)
- Author
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Serge Tatarenko, W. Maslana, B. Piechal, Paulina Plochocka, Piotr Kossacki, J. A. Gaj, Joel Cibert, and Andrzej Golnik
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Condensed Matter::Quantum Gases ,Physics ,education.field_of_study ,Spin polarization ,Absorption spectroscopy ,Condensed Matter::Other ,Oscillator strength ,Exciton ,Population ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter::Materials Science ,Atomic physics ,Trion ,education ,Biexciton ,Quantum well - Abstract
We studied the influence of the populations of neutral and positively charged excitons (trions) on optical absorption of modulation p-doped CdTe-based quantum wells. The density of 2D hole gas in the quantum well was controlled by an additional cw illumination in the range from 10 10 cm -2 to 10 11 cm -2 . Time-resolved absorption was measured following a picosecond, circularly polarized, resonant pump pulse, which created significant exciton population. A spectrally broad femtosecond probe pulse was used to detect the absorption over the excitonic region, including exciton, trion and biexciton transition energies. Besides, we used a small magnetic field (below 1T) to create a steady-state spin polarization of the hole gas. By exploiting polarization-dependent selection rules, we were able to identify exciton, trion and biexciton absorption lines without ambiguity. We studied the evolution of these absorption lines under influence of photo-created populations of excitons and trions. The results are interpreted in terms of spin-dependent exciton-exciton and exciton-carrier interaction, the latter being dominant, in contrast with results obtained on GaAs-based quantum wells. We propose a new explanation of the oscillator strength stealing phenomena observed in doped quantum wells, based on the screening of neutral excitons by charge carriers. We have also found that binding holes into charged excitons excludes them from the interaction with the rest of the system, so that oscillator strength stealing is partially blocked. Experimental evidence is presented for creation of a transient spin polarization in the system by a circularly polarized pump pulse.
- Published
- 2005
7. Control of the spin-polarization of photoelectrons/photoions using short laser pulses (Invited Paper)
- Author
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Takashi Nakajima
- Subjects
Physics ,Superposition principle ,Spin polarization ,Spin states ,Quantum dot ,law ,Excited state ,Photoionization ,Atomic physics ,Laser ,Quantum well ,law.invention - Abstract
We present a scheme to control the spin-polarization of photoelectrons/photoions using short laser pulses. It is based on the pump-probe method. By exciting fine structure manifolds of a system by the short pump pulse with a sufficient bandwidth, a superposition of fine structure states is created. After the pump pulse, the coherently superposed excited state evolves in time under the field-free condition with a period determined by the inverse of energy difference between them. In terms of the spin state, this suggests that the different spin state evolves differently in time, leading to the time-varying spin-polarization. Therefore, varying the time delay between the pump and probe pulses leads to the control of spin states upon photoionization. Specific theoretical results are presented for two-valence-electron atoms, in particular for Mg, which demonstrate that, under certain conditions, not only the degree of spin-polarization but also its polarity can be manipulated through time delay. Furthermore, we propose a new technique to accelerate the coupling time by the introduction of a dressing laser with a few ns duration. Since the underline physics is rather general and transparent, the presented scheme may be potentially applied to nanostructures such as quantum wells and quantum dots.
- Published
- 2005
8. Electronic Structure and Magnetic Properties of the Bulk and (001) Surface of Heusler Alloy Mn2LiGe.
- Author
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SUN Liang, ZHANG Yu, and WANG Qun
- Subjects
MAGNETIC structure ,FERMI surfaces ,HEUSLER alloys ,MAGNETIC properties ,SPIN polarization - Abstract
Using first-principles calculations based on density-functional theory, this paper investigates the electronic structure and magnetic properties of the Heusler alloy Mn2LiGe bulk and its (001) surfaces. The Mn2LiGe bulk is demonstrated to be inverse Heusler alloy with space group of F43m and lattice constant of 5. 87 Å. A direct band gap with a width of 1. 1 eV near the Fermi surface of the spin-down channel is detected. The Mn2LiGe bulk possesses stable half-metallic and magnetism in the lattice constant range of 5. 55 - 6. 33 Å. In addition, six different surface structures of Mn2LiGe are constructed in this paper. The first layer atoms on the surface undergo different displacements, increasing the surface roughness. Due to surface effects, the magnetic properties of atoms on the surface are different compared to those in the bulk. Both the Mn
A MnA and MnB MnB surface structures have the highest magnetic moments, while the LiLi and the GeGe surface structures have the lowest magnetic moments. Electronic structure calculations show that the half-metallic band gap present in the bulk is destroyed in all six surface structures and the spin polarization is weakened in varying degrees. Only the LiLi surface structure maintains up to 99. 9% of the surface spin polarization, making the surface an excellent prospect for applications in spintronic devices. [ABSTRACT FROM AUTHOR]- Published
- 2024
9. Adatom Defect Induced Spin Polarization of Asymmetric Structures
- Author
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Jia Wang, Xuhui Liu, Chunxu Wang, Wanyi Zhang, and Zhengkun Qin
- Subjects
carbon systems ,Full Paper ,General Chemistry ,Full Papers ,electronic states ,spin polarization ,chemical adsorption ,density functional theory - Abstract
The spin polarization of carbon nanomaterials is crucial to design spintronic devices. In this paper, the first‐principles is used to study the electronic properties of two defect asymmetric structures, Cap‐(9, 0)‐Def [6, 6] and Cap‐(9, 0)‐Def [5, 6]. We found that the ground state of Cap‐(9, 0)‐Def [6, 6] is sextet and the ground state of Cap‐(9, 0)‐Def [5, 6] is quartet, and the former has a lower energy. In addition, compared with Cap‐(9, 0) CNTs, the C adatom on C30 causes spin polarization phenomenon and Cap‐(9, 0)‐Def [6, 6] has more spin electrons than Cap‐(9, 0)‐Def [5, 6] structure. Moreover, different adsorb defects reveal different electron accumulation. This finding shows that spin polarization of the asymmetric structure can be adjusted by introducing adatom defects., Two defect asymmetric structures Cap‐(9, 0)‐Def [6, 6] CNT and Cap‐(9, 0)‐Def [5, 6] CNT have been constructed, and the former has a lower energy. In addition, the C adatoms on C30 causes spin polarization phenomenon, and Cap‐(9, 0)‐Def [6, 6] CNT has more spin electrons than Cap‐(9, 0)‐Def [5, 6] CNT.
- Published
- 2022
10. Ultrahigh spin filter efficiency and large spin Seebeck polarization of binuclear manganese phthalocyanine molecular junctions on nickel electrodes.
- Author
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Yin, Shao-Chong, Yu, Jing-Xin, Hou, Zhi-Yu, Liu, Xiu-Ying, and Li, Xiao-Dong
- Subjects
NICKEL electrodes ,SPIN polarization ,DENSITY functionals ,MANGANESE ,DENSITY functional theory ,NEUTRON transport theory ,GREEN'S functions ,HEUSLER alloys - Abstract
In this paper, we investigated the spin transport properties of binuclear manganese phthalocyanine (M n 2 P c 2) spintronic devices sandwiched between two nickel electrodes using the non-equilibrium Green's function method in combination with density functional theory. Based on the calculation results, the M n 2 P c 2 device exhibited excellent spin-filtering capabilities, demonstrating an exceptionally high spin filter efficiency (SFE). Irrespective of the parallel or antiparallel orientation of magnetization in the electrodes, we observed that when both manganese atoms were in a spin-up state, the SFE of spin-resolved currents under finite bias and the thermoelectric currents induced by temperature gradients at fixed temperatures were both close to 100%. The large spin Seebeck polarization of the M n 2 P c 2 device was also obtained at low reference temperatures. This study explores the potential for developing multifunctional spintronic single-molecule devices using Ni − M n 2 P c 2. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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11. Spin Current Enhancement Using Double-Ferromagnetic-Layer Structure for Magnetoelectric Spin-Orbit Logic Device.
- Author
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Ishdorj, Bayartulga, Sharif, Shumaila, and Na, Taehui
- Subjects
MOORE'S law ,SPIN-orbit interactions ,TECHNOLOGICAL innovations ,SPIN polarization ,LOGIC devices ,SPIN-polarized currents - Abstract
The use of Moore's law appears to be coming to an end due to technological and physical constraints, as complementary metal-oxide semiconductor (CMOS) transistors become smaller and closer to the atomic scale. Therefore, various emerging technologies are being researched as potential successors to traditional CMOS transistors, and one of the most exciting candidates is the magnetoelectric spin-orbit (MESO) device. The MESO device comprises two portions (input and output) and it cascades charge/voltage as input and output signals. In the MESO device's output portion, ferromagnetic (FM) and high-spin-orbit-coupling layers are employed to provide spin-polarized current and charge/voltage output. In this paper, we offer a description and analysis of the operating mechanism of the MESO device's output portion using a spin flow approach and propose a double-FM-layer structure. In the double-FM-layer structure, we implement two FM layers with antiparallel magnetization directions, instead of using a single-FM-layer structure to increase the output charge/voltage. The proposed structure is verified through the Verilog-A compact model. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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12. Chirality, vorticity and spin polarization — Experimental overview.
- Author
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Tang, Aihong
- Subjects
CHIRALITY of nuclear particles ,VORTEX motion ,SPIN polarization ,HEAVY ion collisions ,RELATIVISTIC Heavy Ion Collider ,LARGE Hadron Collider - Abstract
In this paper, we provide an exploration of the interrelated topics of chirality, vorticity, and spin polarization in relativistic heavy ion collisions. Our discussion delves into the intricate relationships among these phenomena, examining the recent measurements conducted at both RHIC and LHC.We review the challenges faced, the progress made, and the current state of understanding regarding hot QCD matter under rotation. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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13. Coupling of orbital and spin polarizations to interatomic hopping in a helical atomic chain.
- Author
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Yatabe, Yuya and Akera, Hiroshi
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SPIN polarization ,HELICAL structure ,ELECTRON transport ,TORSION ,MAGNETIC fields ,ATOMIC orbitals - Abstract
Electron transport through a variety of helical structures has been shown to exhibit high-efficiency spin filtering, which is called chirality-induced spin selectivity (CISS). In this paper, we consider a helical chain of atomic p orbitals, which has been employed as a model in exploring the mechanism of CISS in previous theories, and show that the interatomic hopping along the helical chain induces an effective magnetic field (EMF) acting on the atomic orbital angular momentum (OAM). In chains where the curvature and torsion of the helix are small, we find that the EMF on the binormal component of the atomic OAM is created by the curvature, while that on the tangential component is produced by the torsion. We show that such coupling of the atomic OAM and the interatomic hopping leads to current-induced orbital and spin polarizations. We expect that the present coupling, which is expressed locally, can be used to estimate orbital and spin polarizations locally induced in molecules and solids. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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- View/download PDF
14. Theoretical Study on Performing Movement-Related MEG with 83 Kr-Based Atomic Comagnetometer.
- Author
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Chen, Yao, Guo, Ruyang, Wang, Jiyang, Yu, Mingzhi, Zhao, Man, and Zhao, Libo
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NUCLEAR spin ,POLARIZATION (Nuclear physics) ,ALKALI metals ,MAGNETIC fields ,OPTICAL pumping ,SPIN polarization - Abstract
A K–Rb– 83 Kr-based atomic comagnetometer for performing movement-related Magnetoencephalography (MEG) is theoretically studied in this paper. Parameters such as the spin-exchange rates, the spin-dephasing rates and the polarization of the nuclear spins are studied to configure the comagnetometer. The results show that the nuclear spin can generate a magnetic field of around 700 nT, at which the nuclear spin can compensate for a wide range of magnetic fields. In this paper, we also show the fabrication process for hybrid optical-pumping vapor cells, whereby alkali metals are mixed in a glove box that is then connected to the alkali vapor-cell fabrication system. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
15. Electronic and magnetic properties of doped black phosphorene with concentration dependence
- Author
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Min Zhang, Hai Wang, Wei Zhao, Yan Liu, and Ke Wang
- Subjects
Materials science ,doped black phosphorene ,Magnetism ,Band gap ,first principles ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,lcsh:Chemical technology ,01 natural sciences ,lcsh:Technology ,Full Research Paper ,chemistry.chemical_compound ,Nanotechnology ,General Materials Science ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,lcsh:Science ,Spintronics ,Condensed matter physics ,Magnetic moment ,Spin polarization ,Dopant ,lcsh:T ,021001 nanoscience & nanotechnology ,Semimetal ,lcsh:QC1-999 ,0104 chemical sciences ,Nanoscience ,Phosphorene ,chemistry ,electronic properties ,lcsh:Q ,magnetic properties ,0210 nano-technology ,lcsh:Physics - Abstract
In this paper, we employed first-principles calculations and chose Si and S atoms as impurities to explore the concentration-dependence of electronic structure and magnetism of doped phosphorene. It is found that the stability of doped phosphorene improves continuously with increasing the supercell size and decreasing impurity concentration due to the reduction of deformation. The stability of pristine phosphorene is invariable. The band structures of Si- and S-doped phosphorene without spin polarization always show metallic states suggesting the bandgap is insensitive to the in-plane size of the supercell and the dopant content. However, the results are fairly different once the spin polarization is taken into account. The band structures of Si- and S-doped phosphorene become those of a semimetal or a semiconductor as the in-plane size of the supercell goes up to 4 × 4 × 1 or 5 × 5 × 1 and the concentration goes down to 1.56% or 1%, respectively. In addition, we also observe that all Si- and S-doped phosphorene are magnetic, except for the Si-doped phosphorene with 2 × 2 × 1 supercell and a dopant content of 6.25%. The magnetic moment induced by 3p orbit–spin splitting increases with the in-plane size of the supercell, and the largest magnetic moment can be found in 4 × 4 × 1 and 5 × 5 × 1 supercells. These findings offer an alternative method to tune the magnetism and electronic structure of black phosphorene, which might be beneficial for its application in future spintronic devices.
- Published
- 2019
16. Spin selective charge recombination in chiral donor–bridge–acceptor triads.
- Author
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Fay, Thomas P. and Limmer, David T.
- Subjects
SPIN polarization ,CHARGE exchange ,SPIN-orbit interactions ,PHOSPHORESCENCE spectroscopy ,ELECTRON donors ,CHIRALITY of nuclear particles - Abstract
In this paper, we outline a physically motivated framework for describing spin-selective recombination processes in chiral systems, from which we derive spin-selective reaction operators for recombination reactions of donor–bridge–acceptor molecules, where the electron transfer is mediated by chirality and spin–orbit coupling. In general, the recombination process is selective only for spin-coherence between singlet and triplet states, and it is not, in general, selective for spin polarization. We find that spin polarization selectivity only arises in hopping-mediated electron transfer. We describe how this effective spin-polarization selectivity is a consequence of spin-polarization generated transiently in the intermediate state. The recombination process also augments the coherent spin dynamics of the charge separated state, which is found to have a significant effect on the recombination dynamics and to destroy any long-lived spin polarization. Although we only consider a simple donor–bridge–acceptor system, the framework we present here can be straightforwardly extended to describe spin-selective recombination processes in more complex systems. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
17. Spontaneous spin and valley polarizations in a two-dimensional Cr2S3 monolayer.
- Author
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Li, Yan, Wu, Yanzhao, Deng, Li, Yin, Xiang, Han, Xiaoli, Tian, Fubo, and Zhang, Xianmin
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SPIN polarization ,PERPENDICULAR magnetic anisotropy ,MONOMOLECULAR films ,DATA warehousing ,FERROELECTRIC liquid crystals ,ELECTRIC fields - Abstract
Valleytronics has attracted much attention due to its potential applications in information progress and data storage. In this paper, monolayer Cr
2 S3 is proven to be a ferromagnetic (FM) semiconductor by using first-principles calculations. Moreover, monolayer Cr2 S3 exhibits a perpendicular magnetic anisotropy energy of 30 μeV/f.u. Surprisingly, monolayer Cr2 S3 presents spontaneous valley polarization, which means that it will be nonvolatile for data storage. Notably, monolayer Cr2 S3 changes to an antiferromagnetic (AFM) state from the original FM state under biaxial tensile strain, and its easy axis will be reorientated from out-of-plane to in-plane when the compressive strain is larger than −2%. Importantly, for AFM monolayer Cr2 S3 , the valley polarization reversion can be realized by an external electric field along the z direction. In brief, valley polarization has been achieved in both FM and AFM monolayer Cr2 S3 , which is very rare in other valleytronics research. The present research provides a tantalizing candidate for realizing and manipulating valley and spin physics. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
18. Quantitative atomic order characterization of a Mn2FeAl Heusler epitaxial thin film
- Author
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Kurdi, Samer, Sakuraba, Yuya, Masuda, Keisuke, Tajiri, Hiroo, Nair, Bhaskaran, Nataf, Guillaume F, Vickers, Mary E, Reiss, G��nter, Meinert, Markus, Dhesi, Sarnjeet S, Ghidini, Massimo, Barber, Zoe, Kurdi, S [0000-0002-7374-2844], Sakuraba, Y [0000-0003-4618-9550], Masuda, K [0000-0002-6884-6390], Nataf, GF [0000-0001-9215-4717], Meinert, M [0000-0002-7813-600X], Dhesi, SS [0000-0003-4966-0002], Ghidini, M [0000-0002-1905-2455], Apollo - University of Cambridge Repository, Kurdi, Samer [0000-0002-7374-2844], Sakuraba, Yuya [0000-0003-4618-9550], Masuda, Keisuke [0000-0002-6884-6390], Nataf, Guillaume F [0000-0001-9215-4717], Meinert, Markus [0000-0002-7813-600X], Dhesi, Sarnjeet S [0000-0003-4966-0002], and Ghidini, Massimo [0000-0002-1905-2455]
- Subjects
Paper ,spintronics ,Acoustics and Ultrasonics ,Condensed matter ,diffraction ,thin ,x-ray absorption spectroscopy ,Condensed Matter Physics ,spin polarization ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,x-ray magnetic circular dichroism ,Heusler alloy ,x-ray ,x-ray diffraction ,thin films ,films - Abstract
In this work, we investigate the effect of anti-site disorder on the half-metallic properties of a Mn2FeAl Heusler alloy thin film. The film was grown on TiN-buffered MgO 001 substrates via magnetron sputtering. A detailed structural characterization using x-ray diffraction (XRD) and anomalous XRD showed that the film crystallizes in the partially disordered L21 B structure with 33% disorder between the Mn(B) and Al(D) sites. We measure a positive anisotropic magnetoresistance in the film, which is an indication of non-half metallic behaviour. Our x-ray magnetic circular dichroism sum rules analysis shows that Mn carries the magnetic moment in the film, with a positive Fe moment. Experimentally determined moments correspond most closely with those found by density functional calculated for the L21 B structure with Mn(B) and Al(D) site disorder, matching the experimental structural analysis. We thus attribute the deviation from half-metallic behaviour to the formation of the L21 B structure. To realize a half-metallic Mn2FeAl film it is important that the inverse Heusler XA structure is stabilized with minimal anti-site atomic disorder.
- Published
- 2022
19. Negative spin polarization of Mn2VGa Heusler alloy thin films studied in current-perpendicular-to-plane giant magnetoresistance devices.
- Author
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Suto, Hirofumi, Barwal, Vineet, Simalaotao, Kodchakorn, Li, Zehao, Masuda, Keisuke, Sasaki, Taisuke, Miura, Yoshio, and Sakuraba, Yuya
- Subjects
- *
SPIN polarization , *GIANT magnetoresistance , *HEUSLER alloys , *THIN films , *MAGNETIC materials , *FERROELECTRIC thin films - Abstract
Magnetic materials with high negative spin polarization have been sought as a building block to increase the design freedom and performance of spintronics devices. In this paper, we investigate negative spin polarization of Mn2VGa Heusler alloy in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. We fabricated an epitaxial CPP-GMR stack consisting of Mn2VGa/Ag/CoFe with L21 ordering in the Mn2VGa layer and observed negative magnetoresistance (MR), which provided evidence of negative spin polarization. The MR ratio depended on thermal treatments (deposition at an elevated temperature and post-annealing), because these processes affected the ordering, roughness, and magnetic properties of Mn2VGa. The maximum MR ratio reached −1.8% at room temperature and −3.0% at low temperatures, representing the highest among the negative MR values in pseudo-spin-valve CPP-GMR devices despite the underestimation due to an incomplete antiparallel magnetization configuration. These findings demonstrate the potential of Mn2VGa for a material with high negative spin polarization. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
20. Giant magnetoresistance ratio in a current-perpendicular-to-plane spin valve based on an inverse Heusler alloy Ti2NiAl
- Author
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Hongkuan Yuan, Jianwei Li, Hong Chen, Yu Feng, Bo Wu, and Zhou Cui
- Subjects
spin valve ,Materials science ,Magnetoresistance ,nonequilibrium Green’s function ,Spin valve ,General Physics and Astronomy ,Giant magnetoresistance ,02 engineering and technology ,lcsh:Chemical technology ,01 natural sciences ,lcsh:Technology ,spin transport ,Full Research Paper ,Magnetization ,symbols.namesake ,Condensed Matter::Materials Science ,Heusler alloy ,0103 physical sciences ,Nanotechnology ,General Materials Science ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,lcsh:Science ,010302 applied physics ,spintronics ,Condensed matter physics ,Spin polarization ,Spintronics ,Magnetic moment ,lcsh:T ,Fermi level ,current-perpendicular-to-plane geometry ,021001 nanoscience & nanotechnology ,lcsh:QC1-999 ,Nanoscience ,symbols ,lcsh:Q ,0210 nano-technology ,lcsh:Physics - Abstract
A Ti2NiAl inverse Heusler alloy based current-perpendicular-to-plane (CPP) spin valve (SV) with various kinds of atomic terminated interfaces has been designed to explore the potential application of Heusler alloys in spintronics devices. By performing first principles calculations combined with the nonequilibrium Green’s function, it is revealed that spin magnetic moments of interfacial atoms suffer a decrease, and the electronic structure shows that the TiNiB-terminated structure possesses the largest interface spin polarization of ≈55%. Our study on spin-transport properties indicates that the total transmission coefficient at the Fermi level mainly comes from the contribution from the spin up electrons, which are regarded as the majority of the spin electrons. When the two electrodes of the CPP-SV device are in parallel magnetization configuration, the interface containing Ti and Ni atoms possesses a higher spin up transmission coefficient than the interface containing Ti and Al atoms. The device with the TiNiB-terminated interface possesses the largest magnetoresistance ratio of 3.28 × 105, and it has great application potential in spintronics devices.
- Published
- 2019
21. Prediction of fully compensated ferrimagnetic spin-gapless semiconducting FeMnGa/Al/In half Heusler alloys
- Author
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Zhigang Wu, Yajiu Zhang, Z.H. Liu, and X.Q. Ma
- Subjects
spin-gapless semiconductors ,Materials science ,02 engineering and technology ,01 natural sciences ,Biochemistry ,full spin polarization ,Magnetization ,Condensed Matter::Materials Science ,Ferrimagnetism ,0103 physical sciences ,General Materials Science ,FeMn-based ,Electronic band structure ,lcsh:Science ,FeMnGa ,010302 applied physics ,Spin polarization ,Condensed matter physics ,Magnetic moment ,Spintronics ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Research Papers ,Magnetic field ,magnetic inversion symmetry ,Dipole ,Heusler alloys ,Condensed Matter::Strongly Correlated Electrons ,lcsh:Q ,0210 nano-technology ,half-metallic fully compensated ferrimagnets - Abstract
First-principles calculations suggest that C1b-ordered FeMnZ (Z = Al, Ga, In and Al0.5Ga0.5) alloys are half-metallic fully compensated ferrimagnets with a spin-gapless semiconducting nature. In such materials, full spin polarization, spin-gapless properties and absence of external stray fields, thus exhibiting minimal energy losses, are expected., Materials with full spin polarization that exhibit zero net magnetization attract great scientific interest because of their potential applications in spintronics. Here, the structural, magnetic and electronic properties of a C1b-ordered FeMnGa alloy are reported using first-principles calculations. The results indicate that the corresponding band structure exhibits a considerable gap in one of the spin channels and a zero gap in the other thus allowing for high mobility of fully spin-polarized carriers. The localized magnetic moments of Fe and Mn atoms have an antiparallel arrangement leading to fully compensated ferrimagnetism, which possesses broken magnetic inversion symmetry. Such magnetic systems do not produce dipole fields and are extremely stable against external magnetic fields. Therefore, this will improve the performance of spintronic devices. Using this principle, similar band dispersion and compensated magnetic moments were predicted in a C1b-ordered FeMnAl0.5In0.5 Heusler alloy.
- Published
- 2019
22. Band engineering of Co1−xNixS2 with virtual crystal approximation: A first-principles calculations.
- Author
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Rai, D. P. and Ekuma, C. E.
- Subjects
FERMI surfaces ,MAGNETIC alloys ,SPIN polarization ,DOPING agents (Chemistry) ,HILBERT space ,SPIN valves ,ELECTRON transport - Abstract
In this paper, we have explored the electronic and magnetic properties of MS
2 (M = Co , Ni) using first-principles calculations. Our data show rather high tunability of the electronic and magnetic properties of the alloy Co 1 − x Nix S2 (0. 0 ≤ x ≤ 1. 0) with the emergence of half-metallicity that persisted up to the intermediate doping concentration. The half-metallic ground state is characterized by large spin polarization at the Fermi level ( E F ). Beyond the critical doping concentration x ∼ 0. 6 , we obtained a metallic solution followed by an antiferromagnetic ground state at a larger doping concentration. This study provides the underlying physics to understand the low-energy Hilbert space and reports the role of the Fermi surface in controlling the electron transport and thus elucidating the anomalous electronic and magnetic behavior of Co 1 − x Nix S2 . [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
23. Prospects for measuring quark polarization and spin correlations in and samples at the LHC.
- Author
-
Kats, Yevgeny and Uzan, David
- Subjects
SPIN polarization ,QUARKS ,TOP quarks ,STANDARD model (Nuclear physics) ,QUANTUM chromodynamics ,BARYONS - Abstract
Polarization and spin correlations have been studied in detail for top quarks at the LHC, but have been explored very little for the other flavors of quarks. In this paper we consider the processes pp → with q = b, c or s. Utilizing the partial preservation of the quark's spin information in baryons in the jet produced by the quark, we examine possible analysis strategies for ATLAS and CMS to measure the quark polarization and spin correlations. We find polarization measurements for the b and c quarks to be feasible, even with the currently available datasets. Spin correlation measurements for are possible using the CMS Run 2 parked data, while such measurements for will become possible with higher integrated luminosity. For the s quark, we find the measurements to be challenging with the standard triggers. We also provide leading-order QCD predictions for the polarization and spin correlations expected in the and samples with the cuts envisioned for the above analyses. Apart from establishing experimentally the existence of spin correlations in and systems produced in pp collisions, the proposed measurements can provide new information on the polarization transfer from quarks to baryons and might even be sensitive to physics beyond the Standard Model. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
24. Probe beam influence on spin polarization in spin-exchange relaxation-free co-magnetometers.
- Author
-
Wei, Yao, Xing, Li, Zhai, Yueyang, Fan, Wenfeng, Fang, Chi, Liu, Feng, and Quan, Wei
- Subjects
SPIN polarization ,STEADY-state responses ,BLOCH equations ,ELECTRON spin ,CIRCULAR polarization ,OPTICAL pumping - Abstract
Spin-exchange relaxation-free (SERF) co-magnetometers have promising applications in both inertial navigation and fundamental physics experiments. However, the fluctuation in the spin polarization caused by the probe beam has a non-negligible influence on the co-magnetometer signal. In this paper, a theoretical model containing three parameters of the probe beam is established by extending the coupled Bloch equation. Based on this model, the influence of probe power density on the transient and steady-state response of the SERF co-magnetometer is analyzed. According to the transient response model, a new measurement method for transverse optical pumping of the probe beam is proposed. Then, for the steady-state response model, a steady-state error suppression method is suggested by adjusting the degree of circular polarization of the probe beam. Eventually, the suppression method is used to refine the SERF co-magnetometer, achieving a suppression rate of 70.31% in transverse electron spin polarization fluctuations, thus improving the co-magnetometer to a stability of 0.0079
∘ h−1 . To our knowledge, this is better than what has been reported so far. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
25. Spin-reorientation magnetic transitions in Mn-doped SmFeO3
- Author
-
Xiaopeng Cui, Shixun Cao, Jincang Zhang, Baojuan Kang, Venkatesh Chandragiri, Yali Yang, Wei Ren, Xiaolong Qian, Jian Kang, Yifei Fang, Bin Chen, Kai Xu, and Alessandro Stroppa
- Subjects
magnetic phase transitions ,02 engineering and technology ,rare earth perovskites ,spin reorientation transitions ,Rotation ,01 natural sciences ,Biochemistry ,Condensed Matter::Materials Science ,Magnetization ,Condensed Matter::Superconductivity ,Mn doping ,0103 physical sciences ,Antiferromagnetism ,General Materials Science ,Physics::Chemical Physics ,lcsh:Science ,010306 general physics ,Spin (physics) ,Perovskite (structure) ,Condensed matter physics ,Spin polarization ,Chemistry ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Research Papers ,Magnetic field ,Condensed Matter::Soft Condensed Matter ,Ferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,lcsh:Q ,0210 nano-technology - Abstract
Spin-reorientation magnetic transitions are studied in Mn-doped SmFeO3., Spin reorientation is a magnetic phase transition in which rotation of the magnetization vector with respect to the crystallographic axes occurs upon a change in the temperature or magnetic field. For example, SmFeO3 shows a magnetization rotation from the c axis above 480 K to the a axis below 450 K, known as the Γ4 → Γ2 transition. This work reports the successful synthesis of the new single-crystal perovskite SmFe0.75Mn0.25O3 and finds interesting spin reorientations above and below room temperature. In addition to the spin reorientation of the Γ4 → Γ2 magnetic phase transition observed at around T SR2 = 382 K, a new spin reorientation, Γ2 → Γ1, was seen at around T SR1 = 212 K due to Mn doping, which could not be observed in the parent rare earth perovskite compound. This unexpected spin configuration has complete antiferromagnetic order without any canting-induced weak ferromagnetic moment, resulting in zero magnetization in the low-temperature regime. M–T and M–H measurements have been made to study the temperature and magnetic-field dependence of the observed spin reorientation transitions.
- Published
- 2017
26. Efficient Spin Generation in Graphene by Magnetic Proximity Effect Upon Absorption of Far-IR Radiation.
- Author
-
Denisov, K. S. and Golenitskii, K. Yu.
- Subjects
RADIATION absorption ,GRAPHENE ,MAGNETIC insulators ,SPIN polarization ,ABSORPTION coefficients - Abstract
The magnetic proximity effect is significant for atomically thin layers of two-dimensional materials. In this paper, we study the mechanisms of photogeneration spin-polarized carriers in graphene on a magnetic insulator. The magnetic proximity effect and lowered symmetry at the interface enhance the spin response of graphene in the alternating electric field of the incident light. The first leads to spin splitting of the linear spectrum of Dirac electrons. The second increases the role of the spin-orbit interaction. The main mechanisms of photogenerated spin polarization have been considered, including spin flip intersubband and interband transitions, and their contribution to the absorption coefficient of graphene. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
27. Symmetry-Protected Two-Dimensional Half-Semi-Metal NiVS6As2 Monolayer.
- Author
-
Zhu, Meng-xue, Ji, Wei-xiao, Zhu, Hui-wen, Cao, Qiang, and Zhang, Bao-min
- Subjects
QUANTUM Hall effect ,ANOMALOUS Hall effect ,MAGNETIC materials ,SPIN polarization ,FERMI surfaces - Abstract
Two-dimensional (2D) half-metallic magnets are expected to achieve breakthroughs in the field of spintronics and quantum computation due to their 100% spin polarization and non-dissipative ballistic transport characteristics. However, the current availability of practical applications for these materials is limited. In this paper, a new 2D material NiVS
6 As2 is predicted based on density functional theory (DFT). It has a ferromagnetic ground state with a high Curie temperature, TC = 150 K and half-semi-metal (HSM) band structure protected by a structural symmetry degeneracy point on the Fermi surface, which can be controlled by an electric field and strain. When an out-of-plane electric field is applied, NiVS6 As2 shows a Chern insulator with a quantum anomalous Hall (QAH) effect. These results expand the family of 2D magnetic semimetals, and provide new theoretical inspiration for understanding the protection of degenerate point symmetry. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
28. Production, detection, storage and release of spin currents
- Author
-
Michele Cini
- Subjects
General Physics and Astronomy ,lcsh:Chemical technology ,Electric charge ,lcsh:Technology ,Full Research Paper ,Magnetization ,Nuclear magnetic resonance ,Electric field ,Nanotechnology ,General Materials Science ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,lcsh:Science ,quantum transport ,Physics ,spin current ,Spin polarization ,Condensed matter physics ,lcsh:T ,Demagnetizing field ,Magnetostatics ,lcsh:QC1-999 ,Magnetic field ,Nanoscience ,lcsh:Q ,quantum pumping ,Excitation ,lcsh:Physics - Abstract
Background: Quantum rings connected to ballistic circuits couple strongly to external magnetic fields if the connection is not symmetric. Moreover, properly connected rings can be used to pump currents in the wires giving raise to a number of interesting new phenomena. At half filling using a time-dependent magnetic field in the plane of the ring one can pump a pure spin current, excited by the the spin–orbit interaction in the ring.Results: Such a magnetic current is even under time reversal and produces an electric field instead of the usual magnetic field. Numerical simulations show that one can use magnetizable bodies as storage units to concentrate and save the magnetization in much the same way as capacitors operating with charge currents store electric charge. The polarization obtained in this way can then be used on command to produce spin currents in a wire. These currents show interesting oscillations while the storage units exchange their polarizations.Conclusion: The magnetic production of spin currents can be a useful alternative to optical excitation and electric field methods.
- Published
- 2015
29. First-Principles Study of Structural, Electronic, Magnetic and Half-Metallic Properties of Mn2ZrX (X = As, Bi) Full Heusler Alloys.
- Author
-
Khaldi, Ahmed, Zemouli, Mostefa, Benallou, Yassine, Damou, Mehdi, Amara, Kadda, and El Keurti, Mohamed
- Subjects
MAGNETIC properties ,SPIN polarization ,LATTICE constants ,DENSITY functional theory ,MAGNETIC moments ,HEUSLER alloys ,IRON-manganese alloys - Abstract
In this paper, the structural, electronic, magnetic, and half-metallic properties of full-Heusler alloys Mn
2 ZrX (X = As , Bi) in the Hg2 CuTi-type structure have been studied by using the first-principles-based density functional theory (DFT) with the full-potential linearized augmented plane-wave (FP-LAPW) method. Mn2 ZrX (X = As , Bi) compounds are found to be half-metallic ferrimagnets. The calculated total magnetic moments of the Mn2 ZrX (X = As , Bi) alloys are estimated at 01 μ B according to the Slater–Pauling rule of M tot = ( Z tot –24) μ B . It was discovered that Mn2 ZrAs and Mn2 ZrBi maintained their half-metallicity for a lattice constant interval of 5.72 to 6.26 Å and 6.33 to 6.62 Å, respectively, and present a maximum degree of spin polarization at the Fermi level. In addition, the predicted formation energy and elastic parameters show that these materials are mechanically stable. All of these results indicate that these new Mn2 -based heusler alloys are able to be the candidates for spintronic applications. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
30. Kinetic theory for spin-polarized relativistic plasmas.
- Author
-
Seipt, Daniel and Thomas, Alec G. R.
- Subjects
SPIN polarization ,LASER-plasma interactions ,RELATIVISTIC plasmas ,RADIATION - Abstract
The investigation of spin and polarization effects in ultra-high intensity laser–plasma and laser–beam interactions has become an emergent topic in high-field science recently. In this paper, we derive a relativistic kinetic description of spin-polarized plasmas, where quantum-electrodynamics effects are taken into account via Boltzmann-type collision operators under the local constant field approximation. The emergence of anomalous precession is derived from one-loop self-energy contributions in a strong background field. We are interested, in particular, in the interplay between radiation reaction effects and the spin polarization of the radiating particles. For this, we derive equations for spin-polarized quantum radiation reaction from moments of the spin-polarized kinetic equations. By comparing with the classical theory, we identify and discuss the spin-dependent radiation reaction terms and radiative contributions to spin dynamics. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
31. Spin annihilations of and spin sifters for transverse electric and transverse magnetic waves in co- and counter-rotations
- Author
-
Jinsik Mok and Hyoung-In Lee
- Subjects
Angular momentum ,Photon ,General Physics and Astronomy ,orbital ,Poynting ,angular momentum ,spin ,lcsh:Chemical technology ,lcsh:Technology ,Full Research Paper ,Nuclear magnetic resonance ,Nanotechnology ,General Materials Science ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,lcsh:Science ,Spin-½ ,Physics ,Annihilation ,multiplexing ,Spins ,Spin polarization ,lcsh:T ,nanoparticle ,lcsh:QC1-999 ,Nanoscience ,Transverse plane ,Quantum electrodynamics ,trajectory ,Poynting vector ,lcsh:Q ,lcsh:Physics - Abstract
This study is motivated in part to better understand multiplexing in wireless communications, which employs photons carrying varying angular momenta. In particular, we examine both transverse electric (TE) and transverse magnetic (TM) waves in either co-rotations or counter-rotations. To this goal, we analyze both Poynting-vector flows and orbital and spin parts of the energy flow density for the combined fields. Consequently, we find not only enhancements but also cancellations between the two modes. To our surprise, the photon spins in the azimuthal direction exhibit a complete annihilation for the counter-rotational case even if the intensities of the colliding waves are of different magnitudes. In contrast, the orbital flow density disappears only if the two intensities satisfy a certain ratio. In addition, the concepts of spin sifters and enantiomer sorting are illustrated.
- Published
- 2014
32. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments
- Author
-
Mohamed Souhassou, Claude Lecomte, Béatrice Gillon, Nicolas Claiser, M. Deutsch, Jean-Michel Gillet, Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Cristallographie, Résonance Magnétique et Modélisations (CRM2), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Structures, Propriétés et Modélisation des solides (SPMS), Institut de Chimie du CNRS (INC)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Electron density ,Neutron diffraction ,multipole refinement ,Neutron scattering ,Biochemistry ,charge and spin densities ,Nuclear magnetic resonance ,General Materials Science ,Neutron ,Spin-½ ,magnetization density ,Physics ,joint refinement ,Crystallography ,Spin polarization ,Charge density ,General Chemistry ,Condensed Matter Physics ,Research Papers ,polarized neutron diffraction ,QD901-999 ,molecular magnetic materials ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Condensed Matter::Strongly Correlated Electrons ,Density functional theory ,Atomic physics - Abstract
A method to map spin-resolved electron distribution from combined polarized neutron and X-ray diffraction is described and applied for the first time to a molecular magnet and it is shown that spin up density is 5% more contracted than spin down density., Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.
- Published
- 2014
33. Anomalous thermoelectric properties of a Floquet topological insulator with spin momentum non-orthogonality.
- Author
-
Saha, Madhumita and Chowdhury, Debashree
- Subjects
TOPOLOGICAL insulators ,ELECTRIC insulators & insulation ,SPIN polarization ,ATOMIC polarization ,SURFACE states - Abstract
The spin momentum non-orthogonality in 3D topological insulators leads to modification of the spin texture and brings in an out-of-plane spin polarization component. Apart from the spin texture, the anomalous thermoelectric properties of these materials are worth studying. In this paper, we have pointed out that the off resonant light used to irradiate the surface states, induces a gap, which becomes momentum dependent due to the presence of non-orthogonal terms in the Hamiltonian. Importantly, to maintain the off resonant condition of light, the momentum value should satisfy a bound. Furthermore, the momentum dependent gap causes a topological transition at a higher value of momentum, which is important to analyse the unusual double peak structure of the Nernst and electrical conductivities. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
34. Large enhancement of thermoelectric effect by Majorana bound states coupled to a quantum dot.
- Author
-
Hong, Lan, Chi, Feng, Fu, Zhen-Guo, Hou, Yue-Fei, Wang, Zhigang, Li, Ke-Man, Liu, Jia, Yao, Haiyan, and Zhang, Ping
- Subjects
THERMOELECTRIC effects ,QUANTUM states ,MAJORANA fermions ,SPIN polarization ,THERMOELECTRIC power ,QUANTUM dots ,SILICON nanowires - Abstract
This paper presents a theoretical study of the thermoelectric effect in a quantum dot (QD) side-coupled to Majorana bound states (MBSs) formed at the two ends of a Rashba nanowire. In the low-temperature regime favorable for the preparation of MBSs, the magnitude of the thermopower and figure of merit (FOM) are both enhanced by two or three orders of magnitude upon optimizing the QD-MBS coupling strength. In addition, the sign of the thermopower can be reversed by changing the QD-MBS coupling strength, a phenomenon that may be useful for detecting MBSs. The direct overlap between the MBSs also changes the sign of the thermopower and suppresses the magnitude of the FOM at low temperature. However, such an overlap has little influence on the thermopower and FOM at high temperature. In the presence of Zeeman splitting in the QD, the peaks corresponding to spin-up and spin-down thermopowers shift in opposite directions in the QD energy-level space, resulting in a large 100% spin polarization and pure spin thermopower that is crucial in spin caloritronics. Finally, the spin (charge) FOMs are enhanced (reduced) by increasing the Zeeman splitting. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
35. Mechanical and dynamical stability, electronic, magnetic, and thermoelectric properties of RbBaX (X=Si and Ge) half-Heusler compounds.
- Author
-
Boudjeltia, Mohammed Amine, Terkhi, Mohamed Cherif, Aziz, Zoubir, Bennani, Mohammed Abderrahim, and Bouadjemi, Bouabdellah
- Subjects
- *
THERMOELECTRIC materials , *HEUSLER alloys , *SILICON alloys , *DENSITY functional theory , *P-type semiconductors , *ELECTRONIC spectra , *SPIN polarization - Abstract
This research paper explores the structural, electronic, magnetic, elastic, dynamic, and thermoelectric properties of sp-based half-Heusler (HH) RbBaX (X = Si and Ge) compounds using density functional theory (DFT) and the full-potential linearized augmented plane wave (FP-LAPW) method within the WIEN2k software package. We evaluate the exchange correlation potential using two different approaches: The generalized gradient approximation (GGA) and the modified Becke–Johnson approach. We observe that RbBaX (X = Si and Ge) adopts a ferromagnetic configuration based on the analysis of total energy against volume. We establish that these alloys possess a genuine half-metallic character because of the full spin polarization observed at the Fermi level in their electronic spectrum. Both compounds under investigation have a total magnetic moment of 1.00 μ B, in agreement with the Slater–Pauling principle. The Born stability criteria for cubic structures and phonon dispersion patterns confirm the mechanical and dynamic stability of RbBaX (X = Si and Ge) alloys. The thermoelectric properties reveal a p-type semiconductor nature, characterized by significant positive Seebeck values. The thermoelectric figure of merit (ZT) calculated for both alloys at 300 K approaches unity, highlighting their remarkable thermoelectric efficiency. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
36. Boosting the spin polarization and ferromagnetic stability of monolayer C3N through strategic mono-doping and co-doping with copper (Cu) and vanadium (V).
- Author
-
Niu, Yong, Wang, Ying, Wang, Pan, and Zhang, Xiaofei
- Subjects
SPIN polarization ,COPPER ,VANADIUM ,MONOMOLECULAR films ,TRANSITION metals - Abstract
The inherently low spin polarization of ferromagnetism in two-dimensional C
3 N hinders its application in spintronics. Addressing this, the impact of (V, Cu) co-doping on the spin polarization in monolayer C3 N has been systemically explored through first-principles calculations. The results reveal that doping with a single V or Cu atom at an N site significantly enhances spin polarization compared to doping at a C site. Moreover, substituting a single C or N atom with a V atom results in significantly enhanced spin polarization compared to replacement with a Cu atom. Significantly, V and Cu co-doping at different N sites in C3 N systems uniformly favors ferromagnetic states. A remarkable boost in spin polarization is achieved through strategic co-doping of V and Cu at N sites, separated by a distance of 5.681 Å. This enhancement is attributed to the coupling interactions among the C 2p, N 2p, Cu 3d, and V 3d orbitals. The theoretical investigation suggests an effective route to greatly enhance the spin polarization through targeted 3d transition metal co-doping, contributing to the development of high-performance spintronic devices and advancing quantum computing technologies. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
37. Spin polarization in relativistic heavy-ion collisions.
- Author
-
Becattini, Francesco, Buzzegoli, Matteo, Niida, Takafumi, Pu, Shi, Tang, Ai-Hong, and Wang, Qun
- Subjects
- *
SPIN polarization , *HEAVY ion collisions , *QUANTUM field theory , *LOCAL thermodynamic equilibrium , *HYPERONS , *QUARK-gluon plasma , *VECTOR mesons - Abstract
Polarization has opened a new physics chapter in relativistic heavy-ion collisions. Since the first prediction and experimental observation of global spin polarization, a lot of progress has been made in understanding its features, both at experimental and theoretical levels. In this paper, we give an overview on the recent advances in this field. The covered topics include a review of measurements of global and local spin polarization of hyperons and the global spin alignment of vector meson's. We account for the basic theoretical framework to describe spin polarization in a relativistic fluid such as the Quark–Gluon Plasma, including statistical quantum field theory and local thermodynamic equilibrium, spin hydrodynamics, relativistic kinetic theory with spin and coalescence models. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
38. Insights into spin polarization regulated exciton dissociation and charge separation of C3N4 for efficient hydrogen evolution and simultaneous benzylamine oxidation.
- Author
-
Li, Gen, Sun, Xiaomei, Chen, Peng, Song, Meiyang, Zhao, Tianxiang, Liu, Fei, and Yin, Shuang-Feng
- Subjects
SPIN polarization ,PHOTOCATALYTIC oxidation ,ELECTRON spin states ,BENZYLAMINE ,INTERSTITIAL hydrogen generation ,ELECTRON spin ,MAGNETIC fields - Abstract
The employment of spin polarization under an external magnetic field holds great potential for the improvements of photocatalytic performance. However, owing to the huge difference in dielectric properties between ferromagnetic oxide and polymers, the photogenerated excitons with spin states are often limited to the ferromagnetic oxide wells, which leads to unsatisfactory activity. In this paper, a single-atom Co-doped C
3 N4 photocatalyst is successfully synthesized for photocatalytic water splitting and simultaneous oxidation of benzylamine. Under a tiny external magnetic field (24.5 mT), the hydrogen production rate could reach at 3979.0 µmol·g−1 ·h−1 , which is about 340 times that of C3 N4 . Experimental results and theoretical calculations indicate that the interaction of Co d and N p orbital changes the symmetry center of C3 N4 , resulting in an increase in dielectric constant and spin polarization. Moreover, magnetic fields further promote parallel electron spin, and the increased number of charges with the parallel spin-down state is likely to dissociate under the action of an external magnetic field. On the other hand, the Co-N bond provides a huge built-in electric field and active site for strengthening the charge transfer and surface reaction. This work not only deepens the understanding of spin polarization, but also enriches methods to accelerate electron-hole separation. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
39. High efficiency carbon nanotubes-based single-atom catalysts for nitrogen reduction.
- Author
-
Liu, Wei, Guo, Kai, Xie, Yunhao, Liu, Sitong, Chen, Liang, and Xu, Jing
- Subjects
PLATINUM group ,TRANSITION metals ,CATALYSTS ,HYDROGEN evolution reactions ,GIBBS' free energy ,SPIN polarization ,ELECTROLYTIC reduction - Abstract
Carbon-based single-atom catalysts (SACs) for electrochemical nitrogen reduction reaction (NRR) have received increasing attention due to their sustainable, efficient, and green advantages. However, at present, the research on carbon nanotubes (CNTs)-based NRR catalysts is very limited. In this paper, using FeN
3 @(n, 0) CNTs (n = 3 ~ 10) as the representative catalysts, we demonstrate that the CNT curvatures will affect the spin polarization of the catalytic active centers, the activation of the adsorbed N2 molecules and the Gibbs free energy barriers for the formation of the critical intermediates in the NRR processes, thus changing the catalytic performance of CNT-based catalysts. Zigzag (8, 0) CNT was taken as the optimal substrate, and twenty transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Tc, Ru, Rh, Pd, W, Re, Ir, and Pt) were embedded into (8, 0) CNT via N3 group to construct the NRR catalysts. Their electrocatalytic performance for NRR were examined using DFT calculations, and TcN3 @(8, 0) CNT was screened out as the best candidate with a low onset potential of − 0.53 V via the distal mechanism, which is superior to the molecules- or graphene-support Tc catalysts. Further electronic properties analysis shows that the high NRR performance of TcN3 @(8, 0) CNT originates from the strong d-2π* interaction between the N2 molecule and Tc atom. TcN3 @(8, 0) CNT also exhibits higher selectivity for NRR than the competing hydrogen evolution reaction (HER) process. The present work not only provides a promising catalyst for NRR, but also open up opportunities for further exploring of low-dimensional carbon-based high efficiency electrochemical NRR catalysts. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
40. Defect-Induced Modulation of a 2D ZnO/Graphene Heterostructure: Exploring Structural and Electronic Transformations.
- Author
-
Shtepliuk, Ivan
- Subjects
GRAPHENE ,SCHOTTKY barrier ,ZINC oxide ,SPIN polarization ,DENSITY functional theory ,CONDUCTION bands ,IRON clusters - Abstract
This paper presents a theoretical study on the effects of selected defects (oxygen vacancies and substitutional Fe
Zn atoms) on the structural and electronic properties of a 2D ZnO/graphene heterostructure. Spin-polarized Hubbard- and dispersion-corrected density functional theory (DFT) was used to optimize the geometrical configurations of the heterostructure and to analyze the equilibrium distance, interlayer distance, adhesion energy, and bond lengths. Charge density difference (CDD) analysis and band structure calculations were also performed to study the electronic properties of the heterostructure. The results show that the presence of defects affects the interlayer distance and adhesion energy, with structures including oxygen vacancies and FeZn substitutional atoms having the strongest interaction with graphene. It is demonstrated that the oxygen vacancies generate localized defect states in the ZnO bandgap and lead to a shift of both valence and conduction band positions, affecting the Schottky barrier. In contrast, Fe dopants induce strong spin polarization and high spin density localized on Fe atoms and their adjacent oxygen neighbors as well as the spin asymmetry of Schottky barriers in 2D ZnO/graphene. This study presents a comprehensive investigation into the effects of graphene on the electronic and adsorption properties of 2D ZnO/graphene heterostructures. The changes in electronic properties induced by oxygen vacancies and Fe dopants can enhance the sensitivity and catalytic activity of the 2D ZnO/graphene system, making it a promising material for sensing and catalytic applications. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
41. Optoelectronic tuning of Barium titanate doped with Pt: A systematic first-principles study
- Author
-
Mariam Q. Saadon and Hussein A. Miran
- Subjects
Perovskites ,band gap engineering ,Pt–dopant ,absorption ,spin polarization ,Science ,Physics ,QC1-999 - Abstract
In this study, the structural, electronic and optical characteristics of Platinum (Pt)-doped cubic BaTiO 3 perovskite were inspected via density functional theory (DFT) calculations. Generalized gradient approximation (GGA) and Pedraw–Wang 91 (PW91) functional, as applied in CASTEP code, provide an atomic level understanding of the influence of substituting 0.125 Pt dopant at Ba and Ti positions. Results indicate that the optimized lattice parameters and band gap are in good agreement with the experimental and theoretical data. Furthermore, the total and projected density of states (TPDOSs) analysis demonstrates that Pt–dopant integration has an impact on diminishing the band gap and shifting the absorption spectra towards the visible light region. Thus, it is suggested that substituting Ti and Ba atoms with Pt would enhance the optoelectronic characteristics of the host system, due to existing Pt–5d electronic states. Moreover, the negative formation energy values indicate the thermodynamic stability of the modeled configurations. These detailed results provide valuable insights into the physical properties of Pt–BaTiO 3 and its behavior across a range of photon wavelengths. To our knowledge, this contribution evaluates for the first time the influence of introducing platinum (Pt) into a BaTiO 3 perovskite system. The overall findings demonstrate a valuable appraisal of support for experimental synthesis of Pt–BaTiO 3 to serve in various optoelectronic devices.
- Published
- 2024
- Full Text
- View/download PDF
42. Quark condensate and magnetic moment in a strong magnetic field.
- Author
-
Wei, De-Xian and Zhou, Li-Juan
- Subjects
MAGNETIC moments ,MAGNETIC fields ,QUARKS ,MAGNETIC susceptibility ,SPIN polarization ,QUARK models - Abstract
This paper studies the quark condensate, magnetic moment, magnetic polarization, and magnetic susceptibility in a strong external magnetic field by employing the Dyson–Schwinger equations (DSE). The results show these physical quantities as functions of the magnetic field. We note that the quark's spin polarizations are approximately proportional to the magnetic field magnitude. For comparison, we investigate the magnetic moments and susceptibility of the nucleon in the constituent quark model framework and demonstrate that both these quantities increase as the magnetic field rises. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
43. Chiral Crystals, Jack, Conductivity and Magnetism.
- Author
-
Kahr, Bart, Yang, Yongfan, Whittaker, St. John, Shtukenberg, Alexander G., and Lee, Stephanie
- Abstract
Recently, the application of magnetic fields to chiral chemical systems has been rewarding. In a forward‐looking 1986 paper, 'Chiral Metals?', Wallis, Karrer, and Jack D. Dunitz forecast 'that the limitation to proper symmetry elements in a chiral conductor could be associated with the emergence of new properties, those connected with interactions between applied electric and magnetic fields and their internal counterparts.' This was a prescient remark, but it has become manifest in ways that would not have been foreseen in its details by the authors. Here are reviewed the development of chiral conductors broadly imagined by Dunitz and coworkers, based on enantiopure tetrathiafulvalene derivatives that restrict space groups to those that have only symmetry operations of the first kind, as well as the new emergent properties associated with the transport of electrons when magnetic fields are applied to chiral crystals among other systems. These include electrical magnetochiral anisotropy (eMChA), inverse electrical magnetochiral anisotropy (ieMChA), helimagnetism and chirality induced spin selectivity (CISS). The conclusion discussing the circumstances under which achiral TTF crystals becomes chiral, only seems to introduce an oxymoron. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
44. Nonzero-Order Resonances in Single-Beam Spin-Exchange Relaxation-Free Magnetometers.
- Author
-
Wang, Kun, Zhang, Kaixuan, Xu, Nuozhou, Yan, Yifan, Li, Xiaoyu, and Zhou, Binquan
- Subjects
MAGNETIC field measurements ,MAGNETOMETERS ,FLUXGATE magnetometers ,RESONANCE ,SPIN polarization ,MAGNETIC resonance ,CUPRATES ,OPTICAL pumping - Abstract
Zero-field optically pumped magnetometers operating in the spin-exchange relaxation-free (SERF) regime have been extensively studied, and usually depend on zeroth-order parametric resonance to measure the magnetic field. However, the studies conducted on this topic lack thorough analyses and in-depth discussion of nonzero-order magnetic resonances in single-beam SERF magnetometers. In this paper, we analyzed the nonzero-order resonance, especially the first-order resonance, based on a single-beam SERF magnetometer, and discussed its various applications. A comprehensive theoretical analysis and experiments were conducted with respect to multiple functions, including nonzero finite magnetic field measurements, spin polarization measurement, and in situ coil constant calibration. The results showed that first-order resonance can be utilized for nonzerofinite magnetic field measurements, and the spin polarization of alkali-metal atoms can be determined by measuring the slowing-down factor using the resonance condition. Furthermore, acquiring the first-order resonance point at an equivalent zero pump light power through fitting offers an approach for quick and precise in situ coil constant calibration. This study contributes to the applications of SERF magnetometers in nonzero finite magnetic fields. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
45. Loops and polarization in strong-field QED.
- Author
-
Torgrimsson, Greger
- Subjects
MUELLER calculus ,POLARIZED electrons ,SPIN polarization ,POLARIZED photons ,LASER pulses - Abstract
In a previous paper we showed how higher-order strong-field-QED processes in long laser pulses can be approximated by multiplying sequences of 'strong-field Mueller matrices'. We obtained expressions that are valid for arbitrary field shape and polarization. In this paper we derive practical approximations of these Mueller matrices in the locally-constant- and the locally-monochromatic-field regimes. The spin and polarization can also change due to loop contributions (the mass operator for electrons and the polarization operator for photons). We derive Mueller matrices for these as well, for arbitrary laser polarization and arbitrarily polarized initial and final particles. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
46. Vacancy engineering modulates spin polarization to enhance the charge dynamics of CuIn5S8 for photocatalytic sterilization.
- Author
-
Wu, Wenbin, Wang, Jing, Liang, Xiaojie, Luo, Laixi, Yang, Yaohong, Zhou, Fan, Deng, Shuduan, Song, Yumin, Yang, Le, and Kang, Kunyong
- Subjects
STERILIZATION (Disinfection) ,SPIN polarization ,ELECTRON paramagnetic resonance ,ESCHERICHIA coli ,IRRADIATION ,WATER disinfection ,RADIATION sterilization - Abstract
Photocatalytic sterilization technology is a strategy that is environmentally friendly for killing drug-resistant bacteria using solar energy. The role of reactive oxygen species (ROS) required for sterilization depends on the charge separation properties of the photocatalyst. Therefore, we modified the photocatalytic performance of CuIn
5 S8 by fabricating S-vacancies based on the work function (Φ) theory. The spin state density calculations show that S-vacancies lead to spin polarization, and it is easier to separate electrons and holes when their spin directions change. Electron paramagnetic resonance (EPR) results show that Vs -CuIn5 S8 -3 can produce more ROS. Under visible light irradiation, Vs -CuIn5 S8 -3 killed 99% of E. coli and MRSA in natural water within 30 minutes. The work adopted S-vacancies to regulate spin polarization and improve photocatalytic activity, which has great potential in natural water disinfection. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
47. Controllable Spin Filtering by δ-Doping for Electrons in Magnetically and Electrically Modulated Semiconductor Nanostructure.
- Author
-
Kong, Yong-Hong, Fu, Xi, and Li, Ai-Hua
- Subjects
SEMICONDUCTORS ,SPIN polarization ,SPIN-orbit interactions ,ELECTRONS ,SPINTRONICS - Abstract
In this paper, we theoretically investigate how to control spin filtering via a δ -doping for electrons in a magnetically and electrically modulated semiconductor nanostructure (MEMSN), which can be realized by patterning a ferromagnetic (FM) stripe and a Schottky-metal (SM) stripe on top and bottom of GaAs/Al
x Ga 1 − x As heterostructure in experiments, respectively. A considerable spin filtering effect still exists because of spin–orbit coupling (SOC), even if a δ -doping is included. Moreover, spin polarization ratio can be manipulated by δ -doping, which may lead to a structurally-controllable electron-spin filter for semiconductor spintronics. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
48. High polarization sensitivity passive spin Photogalvanic devices based on 2D perovskite CsMnBr4/CsSbCl3Br/CsMnBr4 heterojunction.
- Author
-
Qu, Junyang, Li, Dan, Zhu, Yudong, Yan, Yue, Pang, Yanlan, and Liang, Chunjun
- Subjects
- *
PHOTOCONDUCTIVITY , *GREEN'S functions , *SPIN valves , *OPTOELECTRONIC devices , *SPIN polarization - Abstract
[Display omitted] In recent years, Dion-Jacobson (D-J) perovskite has been extensively studied. In order to further study the application of D-J perovskite materials in spin-optoelectronic multifunctional devices, this paper is based on CsSbCl 3 Br and CsMnBr 4 , a zero-band gap semi-metallic material with the same ferromagnetic ground state and the same crystal structure. In this paper, put forward with transverse CsMnBr 4 /CsSbCl 3 Br/CsMnBr 4 heterojunction optoelectronic devices. The characteristics of photocurrent are discussed using parallel configuration (PC) and anti-parallel configuration (APC) magnetoelectric poles under two conditions: vertical incidence of linearly polarized light and elliptically polarized light utilizing density functional theory and the non-equilibrium Green's function method. The results reveal that the device can achieve complete spin polarization photocurrent, pure spin current, perfect spin filtering effect, and excellent spin valve effect, with high extinction ratios. Under linearly polarized light, the maximum extinction ratio reaches 2747 for the PC configuration and 5200 for the APC configuration. For elliptically polarized light, the extinction ratio is 739 for the PC configuration and reaches a maximum of 240 for the APC configuration. These results indicate that the lateral CsMnBr 4 /CsSbCl 3 Br/CsMnBr 4 heterojunction has broad multi-functional application prospects in the field of optoelectronics and spintronics. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
49. Structure and Phase Composition of Natural Magnesite in 1173–6500 K Temperature Range.
- Author
-
Shekhovtsov, V. V., Abzaev, Yu. A., Volokitin, O. G., Skripnikova, N. K., and Klopotov, A. A.
- Subjects
CUBIC crystal system ,MAGNESITE ,HEXAGONAL crystal system ,THERMAL plasmas ,RIETVELD refinement ,SPIN polarization - Abstract
The paper presents research results of the thermal effect on the structure, phase composition, and morphology of natural magnesite (MgCO
3 ) from the Savinsky deposit (Irkutsk region) used as a raw material. Two types of thermal treatment are applied to test specimens, namely: isothermal exposure at 1173 K and heating and melting in thermal plasma at a bulk temperature of 6500 K. According to the qualitative phase analysis, major phases include MgCO3 and MgO with hexagonal and cubic crystal systems. Complete information is obtained for the lattice structure both in the initial state and after Rietveld refinement of structural parameters. The high-throughput framework Aflow is used to evaluate the phase stability of the crystal lattices using the convex hull construction. The stability plot of MgCO3 and energy color matching are suggested with regard to spin polarization. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
50. Localized d-Electron Effect on Spin Polarization of Vertical Heterostructures of Nanoporous Bilayer Graphene.
- Author
-
Melchakova, Yu. A. and Avramov, P. V.
- Subjects
SPIN polarization ,GRAPHENE ,NANOPOROUS materials ,HETEROSTRUCTURES ,COMPOSITE materials ,INDUCTIVE effect - Abstract
The paper presents a novel composite material based on nanoporous AB-stacked bilayer graphene. The influence of the dopant atom on the electronic properties of the heterostructure and its position in the pore is investigated herein. The proposed effect is considered on composite materials doped with calcium and manganese atoms in order to correctly evaluate the influence of the valence shell filling type without the local field effect caused by the structural properties of an AB-stacked bilayer graphene. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
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