Search

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]

[Display omitted] The efficiency of CO 2 photocatalytic reduction is severely limited by inefficient separation and sluggish transfer. In this study, spin polarization was induced and built-in electric field was strengthened via Co doping in the BiVO 4 cell to boost photocatalytic CO 2 reduction. Results showed that owing to the generation of spin-polarized electrons upon Co doping, carrier separation and photocurrent production of the Co-doped BiVO 4 were enhanced. CO production during CO 2 photocatalytic reduction from the Co-BiVO 4 was 61.6 times of the BiVO 4. Notably, application of an external magnetic field (100 mT) further boosted photocatalytic CO 2 reduction from the Co-BiVO 4 , with 68.25 folds improvement of CO production compared to pristine BiVO 4. The existence of a built-in electric field (IEF) was demonstrated through density functional theory (DFT) simulations and kelvin probe force microscopy (KPFM). Mechanism insights could be elucidated as follows: doping of magnetic Co into the BiVO 4 resulted in increased the number of spin-polarized photo-excited carriers, and application of a magnetic field led to an augmentation of intrinsic electric field due to a dipole shift, thereby extending carrier lifetime and suppressing charges recombination. Additionally, HCOO− was a crucial intermediate in the process of CO 2 RR, and possible pathways for CO 2 reduction were proposed. This study highlights the significance of built-in electric fields and the important role of spin polarization for promotion of photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

In recent years, there has been significant attention towards the development of catalysts that exhibit superior performance and environmentally friendly attributes. This surge in interest is driven by the growing demands for energy utilization and storage as well as environmental preservation. Spin polarization plays a crucial role in catalyst design, comprehension of catalytic mechanisms, and reaction control, offering novel insights for the design of highly efficient catalysts. However, there are still some significant research gaps in the current study of spin catalysis. Therefore, it is urgent to understand how spin polarization impacts catalytic reactions to develop superior performance catalysts. Herein, we present a comprehensive summary of the application of spin polarization in catalysis. Firstly, we summarize the fundamental mechanism of spin polarization in catalytic reactions from two aspects of kinetics and thermodynamics. Additionally, we review the regulation mechanism of spin polarization in various catalytic applications and several approaches to modulate spin polarization. Moreover, we discuss the future development of spin polarization in catalysis and propose several potential avenues for further progress. We aim to improve current catalytic systems through implementing a novel and distinctive spin engineering strategy. [ABSTRACT FROM AUTHOR]

The inherently low spin polarization of ferromagnetism in two-dimensional C3N hinders its application in spintronics. Addressing this, the impact of (V, Cu) co-doping on the spin polarization in monolayer C3N 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 C3N 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]

Spin‐polarized donor radicals based on tetrathiafulvalene (TTF) derivatives and nitronyl nitroxide (NN) radicals in which one‐electron oxidation involves the HOMO instead of the SOMO are well known for exhibiting magnetoresistance. In particular, BTBN consists of one dibromo‐TTF and one NN radical, which are linked by a phenyl coupler group. One of the key factors driving magnetoresistance is the presence of intramolecular ferromagnetic (FM) coupling between the oxidized π‐donor (TTF+⋅, D unit) and NN (R unit). Here, a theoretical study is carried out to assess suitable candidates with enhanced FM coupling with respect BTBN, which is thus used as a reference. The study is conducted via in silico chemical modification of the substituents of the BTBN basic functional units (D and R radicals, C coupler) to benefit from the spin polarization mechanism to boost the intramolecular FM coupling, aiming to distort the BTBN radical arrangement within the molecular crystal as little as possible, in the event the material can be synthesized. NICSiso(1) and Wiberg's Bond Order are analyzed to further assist in identifying promising potential candidates, since the decrease in aromaticity is expected to enhance the diradical character and give rise to a larger magnetic coupling value. The most favorable diradical building block to replace the BTBN moiety results from using a hydroxyl‐ethylene (−(H)C=C(OH)−) as a coupler preserving BTBN original radicals, namely, NN and TTF+⋅ units. This study aims at illustrating the feasibility of improving the intramolecular FM interaction between radical moieties, which is fully realized, as a first step towards the synthesis of new materials with (possibly) enhanced magnetoresistance properties. [ABSTRACT FROM AUTHOR]

We performed spin-torque ferromagnetic resonance studies on the Al/NiFe/AlOx heterostructure. We observed a large non-trivial field-like torque, τ FL z , due to the out-of-plane spin polarization, despite the lack of heavy metal in our multilayer. The torque conductivity is found to be significant with a value equal to σ FL z = (21 ± 2) ℏ 2 e × 10 3 Ω − 1 m − 1 . From a detailed Al thickness dependence, we show that τ FL z arises from the interface between Al and NiFe. We demonstrate that the observed τ FL z arises from the spin-swapping mechanism at the Al/NiFe interface rather than the orbital Hall effect of Al. This observation of a non-trivial spin–orbit torque in the low-cost light element, Al, is highly significant for the energy-efficient control of spintronic devices. [ABSTRACT FROM AUTHOR]

Achieving broad light absorption and high carrier separation efficiency is crucial for wide‐bandgap semiconductors to enable broadband photodetection applications. Here, amorphous gallium oxide nanosheets feature with broad absorption and spin polarization Wis synthesized, and assembled with graphene and p‐Si, realizing UV‒vis‒NIR photodetection. Extended X‐ray absorption fine structure reveals that a‐GaOx NSs possess lower tetrahedral Ga occupation (10%) compared to crystalline β‐Ga2O3 (50%). UV‒vis‒NIR diffuse reflectance spectra and magnetic hysteresis loops demonstrate broad absorption and weak ferromagnetism of a‐GaOx NSs, respectively. Density functional theory calculation further reveals sub‐gap states and spin polarization in a‐GaOx NSs. Moreover, combined with Mott–Schottky curves, photoluminescence and time‐resolved photoluminescence spectra inferred the effective suppression of carrier recombination via spin polarization of a‐GaOx NSs. The graphene/a‐GaOx NSs/p‐Si photodetector incorporates a back‐to‐back rectifying junction, acquiring a dark current as low as 63 pA. All photogenerated carriers are in the depletion region of the photodetector favouring efficient charge separation. This photodetector exhibits a response time of τrise<60 ms and τfall<120 ms, and high specific detectivity 1013 Jones over 254–1064 nm light. [ABSTRACT FROM AUTHOR]

Generating a nonequilibrium spin polarization with a driving force is first realized by the electric current in a system with broken inversion symmetry and extended to that induced by the thermal current and that appearing in an inversionsymmetric system with locally broken inversion symmetry. This article theoretically explores the spin polarization generated by the thermal current and the locally broken inversion symmetry in a symmetric double-quantum well structure (DQWS). This thermally induced spin polarization (TISP) appears in the antiparallel configuration with the TISP of two wells in opposite directions. The calculation using the Boltzmann equation in the relaxation-time approximation under the condition of zero charge current shows that the local TISP exhibits the maximum at a finite Rashba spin-orbit interaction when the electron density is fixed. This is because the local TISP in the DQWS is enhanced at the chemical potential near the bottom of the first-excited sub-band. This enhancement also occurs in a single quantum well with globally broken inversion symmetry. Another finding is that the maximum of the local TISP appears at a nonzero interwell coupling. The spin current by the diffusion of the local TISP into an adjacent electrode is also calculated. [ABSTRACT FROM AUTHOR]

Fe-based catalysts have a good prospect in oxygen reduction reaction (ORR) in fuel cells. However, the catalytic activity of Fe-based catalysts requires further improvement to satisfy the demand in industrial application and the working mechanism is still shrouded in ambiguity. Here, a ferromagnetic catalyst with nitrogen-doped carbon supported FeCoNi alloy was synthesized by impregnation-pyrolysis method. The micromorphology and structure of the catalyst was analyzed by XRD, SEM, TEM, XPS, BET and Raman spectroscopy. The trimetallic catalyst showed high ORR activity in 0.1 M KOH with a half-wave potential of 0.908 V and a limiting current density of 6.153 mA cm−2, which was superior to 20 % Pt/C. The synergistic effect of FeCoNi alloy regulated the spin polarization and the regulated spin state improved ORR performance by facilitating the adsorption of O 2 molecules and the conversion of the activated intermediates. [Display omitted] • FeCoNi@NC is derived from C 3 N 4 by impregnation-pyrolysis method. • FeCoNi@NC is highly active for oxygen reduction reaction. • The spin polarization is regulated by the synergistic effect of Fe, Co and Ni. [ABSTRACT FROM AUTHOR]

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 CuIn5S8 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-CuIn5S8-3 can produce more ROS. Under visible light irradiation, Vs-CuIn5S8-3 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]

Multiferroic van der Waals (vdW) heterostructures offer an exciting route toward the nanoelectronics and spintronics device technology. How to realize the mutual regulation between ferroelectric and magnetic materials has attracted extensive research. In this work, based on the density functional theory, we simulate a vdW multiferroic heterostructure based on the bipolar magnetic semiconductor material graphone and ferroelectric monolayer In2Te3 and further investigate its electronic properties. We find that direct contact between In2Te3 and graphone induces a transition in graphone from a ferromagnetic state to a non-magnetic state. Fortunately, the magnetic properties of graphone are preserved by using graphene as an intercalation layer, and the graphone monolayer changes from its original semiconductor to a half-metal in the graphone/graphene/In2Te3 vdW heterostructure for P↓ state. Furthermore, by adjusting the layer spacing of the heterostructure, the spin polarization states of graphone at the Fermi level (EF) are regulated between spin-up (S↑) and spin-down (S↓) with the reversal of ferroelectric polarization states. Our results not only provide a promising way to realize the half-metallicity in 2D magnetic materials but also computationally predict the ferroelectric control of the spin polarization state, which has great application potential in the next-generation nonvolatile electrically controlled spintronic devices. [ABSTRACT FROM AUTHOR]

We investigate the spin-dependent spin-polarization and transport properties in altermagnet-based resonant tunneling junctions, in which the altermagnet has two symmetric orientations of spin-split Fermi surface. In the first model the Fermi surface is an ellipse with the major axes either parallel or perpendicular to the altermagnet/barrier interface, and the Fermi surface in the second one is also an ellipse but the major and the minor axes have the same angle relative to the altermagnet/barrier interface. Our findings reveal that the transport properties for spin-up and spin-down electrons are spin polarized and depend on the orientation of the altermagnet with respect to the interface. In contrast to conventional ferromagnetic and antiferromagnetic splitting mechanisms, the transmission in our study exhibits spin splitting with an alternating sign. For the first model, the total spin-polarization is zero, indicating a lack of net magnetization due to the combined effects of spin and real-space symmetries, thereby reflecting normal metal properties. Conversely, in the second model, a discernible total spin-polarization emerges, indicative of ferromagnetism. These orientation-dependent transport properties exemplify the unique features of the altermagnetism. The anisotropic altermagnetic state in momentum space can be measured by the orientation-dependent conductance in these resonant tunneling junctions.

Abstract The magnetic proximity effect can induce a spin dependent exchange shift in the band structure of graphene. This produces a magnetization and a spin polarization of the electron/hole carriers in this material, paving the way for its use as an active component in spintronics devices. The electrostatic control of this spin polarization in graphene has however never been demonstrated so far. We show that interfacing graphene with the van der Waals antiferromagnet CrSBr results in an unconventional manifestation of the quantum Hall effect, which can be attributed to the presence of counterflowing spin-polarized edge channels originating from the spin-dependent exchange shift in graphene. We extract an exchange shift ranging from 27 – 32 meV, and show that it also produces an electrostatically tunable spin polarization of the electron/hole carriers in graphene ranging from − 50% to + 69% in the absence of a magnetic field. This proof of principle provides a starting point for the use of graphene as an electrostatically tunable source of spin current and could allow this system to generate a large magnetoresistance in gate tunable spin valve devices.

Spin polarized electron beams have wide applications in high energy physics. The generation of such electron beams has recently attracted considerable attention where the collision of intense laser pulses with high energy electron beams is proposed as one of the potential methods. In previous numerical studies, different spin-quantization axes (SQA) are used, which lead to different calculation results in some configurations of laser interaction with an electron beam. To be consistent with the well-known Thomas–Bargmann–Michel–Telegdi (TBMT) equation, we have proposed a new SQA which is along the TBMT precession direction. We clearly show the difference among the three kinds of SQA selections by comparing the temporal evolution of the electron beam's polarization during the perpendicular collision of an electron beam with s-polarized two-color laser pulses, where the magnetic fields have a parallel component along the electron motion direction. Calculation shows that such differences could be experimentally measured by nowadays facilities. To get the maximum electron polarization degree in the two-color laser pulses based schemes, we also find the optimized condition for the two-color laser parameters. Our studies give a better understanding of spin-polarization calculation and will be beneficial for future experimental designs for electron polarization manipulation. [ABSTRACT FROM AUTHOR]

With the field correlator method (FCM) for QCD, we show that the chiral vortical effect (CVE) in hot (strongly-interacting) quark-gluon plasma ((s)QGP) is modified by non-perturbative interactions – by color-magnetic confinement, and by remnant color-electric interaction, which is encoded in the Polyakov line. The obtained result demonstrates numerical suppression of CVE comparable to the phenomenological suppression used for numerical simulations of RHIC-STAR data on hyperons spin polarization in non-central heavy ion collision (HIC). The parameters range in the temperature – quark chemical potential plane is expected to cover ALICE and RHIC data. The chiral current is calculated for the rigidly rotating model of (s)QGP in the linear order in angular velocity at the rotation axis with account of non-perturbative interactions. [ABSTRACT FROM AUTHOR]

Abstract One of the key challenges for spintronic and quantum technologies is to achieve active control of the spin angular momentum of electrons in nanoscale materials on ultrafast, femtosecond timescales. While conventional ferromagnetic materials and materials supporting spin texture suffer both from conceptional limitations in miniaturization and inefficiency of optical and electronic manipulation, non-magnetic centrosymmetric layered materials with hidden spin polarization may offer an alternative pathway to manipulate the spin degree of freedom by external stimuli. Here we demonstrate an approach for generating transient spin polarization on a femtosecond timescale in the otherwise spin-unpolarized band structure of the centrosymmetric 2H-stacked group VI transition metal dichalcogenide WSe2. Using ultrafast optical excitation of a fullerene layer grown on top of WSe2, we trigger an ultrafast interlayer electron transfer from the fullerene layer into the WSe2 crystal. The resulting transient charging of the C60/WSe2 interface leads to a substantial interfacial electric field that by means of spin-layer-valley locking ultimately creates ultrafast spin polarization without the need of an external magnetic field. Our findings open a novel pathway for true optical engineering of spin functionalities such as the sub-picosecond generation and manipulation of ultrafast spin currents in 2D heterostructures.

Abstract With the field correlator method (FCM) for QCD, we show that the chiral vortical effect (CVE) in hot (strongly-interacting) quark-gluon plasma ((s)QGP) is modified by non-perturbative interactions – by color-magnetic confinement, and by remnant color-electric interaction, which is encoded in the Polyakov line. The obtained result demonstrates numerical suppression of CVE comparable to the phenomenological suppression used for numerical simulations of RHIC-STAR data on hyperons spin polarization in non-central heavy ion collision (HIC). The parameters range in the temperature – quark chemical potential plane is expected to cover ALICE and RHIC data. The chiral current is calculated for the rigidly rotating model of (s)QGP in the linear order in angular velocity at the rotation axis with account of non-perturbative interactions.

Photocatalytic and photoelectrochemical water splitting using semiconductor materials are effective approaches for converting solar energy into hydrogen fuel. In the past few years, a series of photocatalysts/photoelectrocatalysts have been developed and optimized to achieve efficient solar hydrogen production. Among various optimization strategies, the regulation of spin polarization can tailor the intrinsic optoelectronic properties for retarding charge recombination and enhancing surface reactions, thus improving the solar-to-hydrogen (STH) efficiency. This review presents recent advances in the regulation of spin polarization to enhance spin polarized-dependent solar hydrogen evolution activity. Specifically, spin polarization manipulation strategies of several typical photocatalysts/photoelectrocatalysts (e.g., metallic oxides, metallic sulfides, non-metallic semiconductors, ferroelectric materials, and chiral molecules) are described. In the end, the critical challenges and perspectives of spin polarization regulation towards future solar energy conversion are briefly provided. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) is a crucial cathode reaction for developing quasi‐solid zinc–air batteries (QZABs) with high energy density. However, the activity and stability of catalysts under extreme conditions have not been fully explore. Herein, a series of systematic experiments and theoretical calculations have been conducted to investigate the potential of introducing FexCoy into nitrogen (N)‐doped porous carbon (NPC) via one‐step pyrolysis to form a core–shell structure that can effectively enhance the activity of the catalysts, particularly at low temperatures. Due to the difference in the work function of 5.12, 5.11, and 5.06 eV, the spin‐polarized charge is transferred to the pyridinic‐N site on the surface under the charge transfer. Consequently, the pyridinic‐N site on the surface exhibits varying degrees of magnetic moment 0.024 µB, which is crucial for forming OOH* and enhances ORR activity. The Fe5Co5@NPC catalyst is evaluated for QZABs at −40 °C and achieved a power density of up to 117.6 mW cm−2, which is only 18.7% lower than normal temperature, and a cycle life of up to 300 h. This study provides a means to realize the design of QZABs catalysts in extreme environments and explore their application potential. [ABSTRACT FROM AUTHOR]