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In this study, we present results of a comprehensive computational and experimental study of CoFeVAl and CoFeV0.5Mn0.5Al Heusler alloys. It is shown that while CoFeVAl exhibits a fairly large degree of spin polarization, this material is not half-metallic due to the presence of the vanadium spin-down states at the Fermi level. However, replacing 50% of vanadium with manganese results in a nearly half-metallic transition, largely due to the shift of the Fermi level towards occupied states. Moreover, the half-metallicity of CoFeV0.5Mn0.5Al is rather robust in a wide range of considered mechanical strain and under experimentally observed B2-type atomic disorder, thus making this alloy potentially suitable for practical spintronic applications. Both considered alloys exhibit ferromagnetic alignment at larger lattice constants, aside from a relatively small magnetic moment of vanadium which is anti-aligned with the magnetic moments of Co, Fe and Mn. We have synthesized both CoFeVAl and CoFeV0.5Mn0.5Al alloys in cubic structure with some structural disorder using arc melting and annealing. The structural and magnetic properties of the synthesized CoFeV0.5Mn0.5Al alloy are in good agreement with the theoretical calculations but vary slightly from the parent compound. [ABSTRACT FROM AUTHOR]

In this work, we theoretically investigate the phenomenon of spin polarization in generalized Sierpinski gasket (SPG) triangles ( Δ N N N , Δ F N N , Δ F F N , Δ F F F) in the presence of Rashba spin–orbit interaction (RSOI) within a tight-binding framework. The geometrical construction is addressed for all four types of generalized SPG triangles using an iterative function system that begins with a fixed triangle of any arbitrary side length. The geometry of various types of fractal networks has a major impact on the degeneracy of the energy spectrum. It is shown that only the two-terminal setup in the presence of RSOI is incapable of breaking the spin degeneracy, which necessitates the use of a three-terminal setup to break the time-reversal symmetry. The effect of flip map induced anisotropic hopping integrals on three-terminal spin-resolved transmission probabilities is studied. In several cases, we find almost 100 % spin polarization in our considered lattices. We also analyze how spin polarization varies with RSOI strength and fractal generations. Our results indicate that fractal lattices might be suitable functional elements for designing future spin-based electronic devices. [ABSTRACT FROM AUTHOR]

We have theoretically investigated the Andreev reflection (AR)-induced conductance spectra through antiferromagnet/normal layer/superconductor junctions with hexagonal lattices. When the PT symmetry is broken by the staggered sublattice potential, antiferromagnet may exhibit spin polarization. A gap-edge conductance peak is usually shown, reflecting the characteristic of conventional AR. Equal-spin AR can be generated by the spin-flip scattering caused by Rashba spin–orbit coupling in the normal layer. Surprisingly, when the equal-spin AR process dominates, the conductance peak divides into two peaks near the singlet-gap energy, indicating the existence of spin-triplet pairings in the antiferromagnet. Furthermore, as the amplitudes of the conventional and equal-spin ARs can be modulated by the staggered sublattice potential and electrostatic potential, a conversion from the conductance peak to the conductance peak splitting can be realized, which can help us to distinguish between the spin-singlet and spin-triplet pairings. These findings make the antiferromagnet/superconductor junctions as promising platforms for future superconducting spintronics applications. [ABSTRACT FROM AUTHOR]

Inspired by potential application prospects of spintronics and valleytronics, a novel heterobilayer Janus structure is designed by replacing the chalcogenide atomic layers in the original bilayer MoS2. Based on first-principles calculations, it is found that the SMoS/SeMoS structure exhibits a direct band-gap semiconductor and a typical type-II band alignment with longer carrier lifetime. The transition metal (TM) atom represented by V/Cr/Mn can be stably adsorbed on the heterobilayer Janus SMoS/SeMoS sheet and effectively introduce magnetic moments (m). The calculation results demonstrate that the most stable adsorption site of the TM atom is CX(A), and the TM (V/Cr/Mn) adatom modified SMoS/SeMoS system is converted into metal (V-) or half-metal (Cr/Mn-), respectively. Under the coupling of different indirect exchange interactions, the structure exhibits stable intrinsic anti-ferromagnetic interactions for V-SMoS/SeMoS and ferromagnetic ground state for Cr/Mn-SMoS/SeMoS, respectively, and the magnetic transition temperature (T c) reaches a high temperature or even room temperature. Moreover, the robust out-of-plane magnetocrystalline anisotropy energy ensures stable long-range magnetic order. Specifically, the combination of spin injection and strong spin–orbit coupling interaction effectively breaks the time-reversal symmetry, which leads to valley polarization of the system. Based on this, the biaxial strain can effectively regulate the electronic structure, magnetic properties and valley polarization of TM-SMoS/SeMoS nanosheets with double breaking of spatial-inversion and time-reversal symmetry. [ABSTRACT FROM AUTHOR]

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]

We investigated the Ge-composition (Îł) dependence of the saturation magnetization of Co2Fe(Ga, Ge) (CFGG) thin films and the magnetoresistance (MR) ratio of CFGG-based current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices together with first-principles calculations of the electronic states of CFGG. Theoretical calculations showed that spin polarization is highest at the stoichiometric composition Îł = 0.56 in Co2Fe1.03Ga0.41Ge Îł and that it decreases in off-stoichiometric CFGG, mainly due to the formation of CoFe antisites for Ge-deficient compositions and FeCo antisites for Ge-rich compositions, where CoFe (FeCo) indicates that Co (Fe) atoms replace the Fe (Co) sites. The saturation magnetic moment (ÎĽ s) per formula unit decreased monotonically as Îł increased from 0.24 to 1.54 in Co2Fe1.03Ga0.41Ge Îł. The ÎĽ s was closest to the Slaterâ€"Pauling value predicted for half-metallic CFGG at the stoichiometric composition Îł = 0.56, indicating that stoichiometric CFGG has a half-metallic nature. This is consistent with the result for the theoretical spin polarization. In contrast, the MR ratio of CFGG-based CPP-GMR devices increased monotonically as Îł increased from 0.24 to 1.10 and reached an MR ratio of 87.9% at the Ge-rich composition Îł = 1.10. Then, the MR ratio decreased rapidly as Îł increased from 1.10 to 1.48. Possible origins for the slight difference between the Ge composition at which the highest MR ratio was obtained (Îł = 1.10) and that at which the highest spin polarization was obtained (Îł = 0.56) are improved atomic arrangements in a Ge-rich CFGG film and the reduction of effective Ge composition due to Ge diffusion in the GMR stacks. [ABSTRACT FROM AUTHOR]

The impact of inter-valley scattering in modifying the density of optically injected spin polarized electrons in AlxGa1−xAs/GaAs heterostructure is investigated. Polarization resolved photoluminescence excitation measurements are performed for studying the spectral dependence of degree of circular polarization (DCP) of photoluminescence signal emanating from an adjacent quantum well layer. The experimental DCP spectra is found to deviate from the theoretically calculated curve at high excitation energy and the deviation is seen to widen with the Al-content of AlxGa1−xAs barrier layer. In the past, researchers had attributed similar deviations to the Dyakonov–Perel (DP) spin relaxation mechanism which dominates the electrons spin dynamics at high excitation energy. However, we find that the inter-valley scattering along with the DP mechanism decide the shape of optical spin orientation spectra at higher energy. In fact, at higher Al-content, the inter-valley scattering in AlxGa1–xAs layer becomes the most dominant mechanism to govern the steady state electron spin polarization at the band edge. A numerical model is also proposed for estimating the steady state electron spin polarization at zone centre by including the inter-valley scattering, energy relaxation and DP spin relaxation mechanisms. [ABSTRACT FROM AUTHOR]

Perfect polarization of spin and valley is found to coexist in the proposed junction of monolayer MoS2. The junction consists of two barriers modulated by off-resonant circularly polarized light and spin Zeeman field, respectively. By appropriately altering the modulation, we can achieve all four combinations of simultaneous perfect spin and valley polarization, which are , , , and. Moreover, we have found that by continuously tuning the light illuminating the junction, the valley polarization will abruptly dive from 100% to −100%. The spin polarization exhibits similar features when we tune the spin Zeeman field. Thus, the valley switching effect and the spin switching effect are realized in monolayer MoS2 by varying the circularly polarized light and spin Zeeman field. These results demonstrate the modulated monolayer MoS2's potential as a vital tool in spintronics and valleytronics. [ABSTRACT FROM AUTHOR]

In this work, we address the fundamental question of whether a magnetic material having zero net magnetization can produce polarized spin current from a completely unpolarized one. Common wisdom suggests that this is not possible, but if we break the symmetry in hopping integrals in different segments of the magnetic sample, then a finite possibility of getting polarized spin current is established. To substantiate this fact, we consider a one-dimensional magnetic chain with vanishing net magnetization where one part of the chain is subjected to an ac electric field, keeping the other part free. The ac field, introduced through Peierls substitution, modulates the hopping integrals yielding a misalignment of up and down spin channels, which is the primary requirement to get finite spin polarization. Simulating the system within a tight-binding framework, we compute spin-dependent transmission probabilities using the well-known Green's function prescriptionand determine junction currents following the Landauer–Büttiker formalism. Our analysis may shed some light on designing spin-polarized devices using driven magnetic materials with vanishing net magnetization. [ABSTRACT FROM AUTHOR]

Controlling the spin polarization of a 2D semiconductor through the proximity effect is an appealing approach for creating next generation spintronic devices; however, experiments showing the feasibility of this method are still limited. Here, we present a review of efforts intended to directly measure the spin polarization of monolayer graphene and h-BN coupled to a magnetic substrate. When considered together these studies conclusively show that 2D monolayers can obtain a spin polarization that is dependent on the magnetization of the underlying substrate, and, in some cases, can be comparable to the spin polarization of conventional ferromagnets. [ABSTRACT FROM AUTHOR]

Organic multiferroic tunnel junctions (OMFTJs) with multi-resistance states have been proposed and have drawn intensive interests due to their potential applications, for example in memristor and spintronics based synapse devices. The ferroelectric control of spin polarization at a ferromagnet/ferroelectric organic (FE-Org) interface by electrically switching the ferroelectric polarization of the FE-Org has been recently realized. However, there is still a lack of understanding of the transport properties in OMFTJs, especially the interplay between the ferroelectric domain structure in the organic barrier and the spin polarized electron tunneling through the barrier. Here, we report on a systematic study of the temperature dependent transport behavior in La0.6Sr0.4MnO3/PVDF/Co OMFTJs. It is found that thermal fluctuation of the ferroelectric domains play an important role on the transport properties. When T > 120 K, the opposite temperature dependence of resistance for up and down ferroelectric polarization states results in a rapid diminishing of the tunneling electroresistance. These results contribute to the understanding of the transport properties for designing high performance OMFTJs for memristor and spintronics applications. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "High Spin Polarization in All-3d-Metallic Heusler Compounds: The Case of Fe2CrZ and Co2CrZ (Z=Sc, Ti, V)" published in the Journal of Physics D: Applied Physics in 2019. The correction addresses errors in the caption of figure 4 and the first paragraph of subsection 3.3. The errors are related to the representation of the bands and the number of electrons in the minority-spin states. The correction does not affect the final conclusions of the paper. [Extracted from the article]

Spin-polarized electron transport through the zigzag graphene nanoribbon (ZGNR) is investigated by assuming that it couples with different charomium triiodide (CrI3) geometries, respectively. That is to say that the ZGNR either absorbs the monolayer CrI3 or one CrI3 molecule, or couples laterally with one CrI3 molecule. It is found that the spin polarization in the electron transport process is tightly dependent on the CrI3 geometry and the ZGNR-CrI3 coupling manner. When the CrI3 molecule is absorbed on the surface of the ZGNR, the spin-polarization efficiency is much higher than the other two cases, accompanied by the wide spin-polarization region. This work provides a new kind of scheme for optimizing the spin polarization in graphene-based materials. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the spin polarization from two-dimensional hole gases (2DHG) formed in p–i–p GaAs/AlAs resonant tunnelling diodes (RTDs) under magnetic field parallel to the tunnel current. We have observed that the polarization degree from the quantum well (QW) and the 2DHG formed at the accumulation layer is highly voltage and light sensitive and exhibits a clear sign inversion. Our results indicate that the voltage dependence of the QW polarization degree is mainly due to an efficient hole-resonant tunnelling process through spin states of the QW. On the other hand, the voltage dependence of the 2DHG polarization degree seems to be dependent on the hole density which is controlled by the applied voltage across the RTDs. [ABSTRACT FROM AUTHOR]

By means of ab initio calculations within density-functional theory, the structural, electronic and magnetic properties of a zigzag-edged graphene nanoribbon (ZGNR) with 3d transition-metal atoms (TMAs) (Sc–Zn) embedded in the periodically distributed single vacancies are systematically studied. Different from the pristine ZGNR, all of these composite structures show the subband structures with nontrivial spin polarizations, regardless of the type and the embedding position of the TMA. Embedding one kind of these atoms (V, Cr, Ni, Cu or Zn) near one ribbon edge can cause a notable edge distortion. Except for the cases of Sc, Fe and Co doping, other kinds of TMAs embedded near an edge of the ribbon can suppress the inherent magnetism of the zigzag edge. By further analysis, we find that two effects are responsible for the suppression of edge magnetism. One is the variation of the occupied spin-polarized subbands due to the hybridization of the edge state of the ZGNR and 3d atomic states of the dopant. The other is the delocalization of the edge state caused by the exotic TMA. The unilateral magnetism of these TMA-embedded ZGNRs can be utilized to realize the spin-polarized electronic transport, which is the key electronic property in the context of spintronics applications of carbon-based materials. [ABSTRACT FROM AUTHOR]

The trilayer system MgO/Au monolayer/Fe was investigated by hard x-ray photoemission experiments in combination with the standing-wave technique. The insertion of the Au layer into the Fe/MgO tunnel junction provides an additional handle to influence the properties of the interface. The recently explored method of standing-wave excited hard x-ray photoemission was used to investigate both the structural properties and chemical states of the interfacial layers in one experiment. The results show that the Au monolayer does not grow as a closed layer, but intermixes strongly with the Fe below. This behaviour results in a very sharp interface between the Au/Fe and the MgO layer on top. However, the XPS spectra show no hint for a formation of FeO at the interface. [ABSTRACT FROM AUTHOR]

Here, we use half-metallic Co2MnSi (CMS) ferromagnets to prepare CMS/Ag non-local lateral spin valve devices. By optimizing the structural property of CMS wires and the interface quality, device structure of CMS/Ag spin valves, large spin resistance about 4.2mγ can be observed clearly at room temperature when the gap length of two CMS wires is 200 nm. By fitting the spin accumulation signals, we obtained that the spin diffusion length for Ag wire is 290 nm and the spin polarization for CMS wires is 74%. These results indicate that half-metallic ferromagnetic materials can be used in semiconductor-based spin devices. [ABSTRACT FROM AUTHOR]

We investigated the effects of Mn ions on the spin dynamics of electrons confined in a semiconductor quantum well nearby a Mn-based ferromagnetic layer. Circularly polarized Hanle and time-resolved photoluminescence (PL) measurements were carried out on a set of samples with different Mn delta-doping concentrations. We observe a strong influence of the Mn layer for both the electron lifetime and its spin-relaxation time for high-Mn concentrations, when the electrons significantly overlap with Mn ions. Our results also show that the circular-polarization degree obtained by simple continuous-wave PL measurements is not sufficient to determine the relaxation dynamics due to a compensation effect of the lifetime and the spin-relaxation time. (Some figures may appear in colour only in the online journal) [ABSTRACT FROM AUTHOR]

Co/C granular films with 3-21% Co content are fabricated by facing-target magnetron sputtering. As the Co content increases, the isolated Co particles in the a-C matrix gradually connect with each other, and consequently the electrical transport of the Co/C films changes from insulating to metallic conduction. The insulating samples show spin-dependent negative magnetoresistance (MR), which is related to the alignment of the spins at the interface between Co particles and the carbon matrix. Interfacial spin polarization P0 is related to the amount of interfacial hybridization, which is influenced by the size of sp² carbon clusters in the a-C matrix. Metallic samples show the competition of negative MR and positive linear MR. Negative MR observed at low temperatures is caused by a weak localization effect and is suppressed when the magnetic field is above 15 kOe. Positive linear MR is observed at high fields and high temperatures, and could be explained by quantum electron-electron interaction theory. The magnetotransport properties in the Co/C films are significantly influenced by the configuration of Co particles and, consequently, the conduction regime rather than the size of sp2 carbon clusters in the a-C matrix. [ABSTRACT FROM AUTHOR]

Epitaxial La0.67Sr0.33MnO3 films grown on orthorhombic NdGaO3 (0 0 1) substrates show predominantly uniaxial magnetic anisotropy. On cooling, we observe the growth of a biaxial contribution, which we quantify by fitting magnetometry data to a coherent rotation model. A film grown under deliberately sub-optimal conditions shows a relatively stronger biaxial contribution that results in a significant population of transverse magnetic domains below ~200 K, as revealed by photoemission electron microscopy with x-ray magnetic circular dichroism contrast. Care should be taken to avoid these transverse domains in spintronic devices designed to exploit the high low-temperature spin-polarization of La0.67Sr0.33MnO3. [ABSTRACT FROM AUTHOR]

We perform a systematic investigation of MnPSe3/CrBr3 two-dimensional (2D) van der Waals heterostructures through first-principles calculations. The most stable stacking configuration of MnPSe3/CrBr3 heterostructures is found to have an indirect type-II band structure. Biaxial tensile strain is employed to tailor the spin–valley properties of the heterostructures in terms of the momentum, energy and spin components of the valleys. A novel opposite spin splitting evolution appears at the K and K′ valleys of the top valance band (TVB) with increasing tensile strain. A change from an indirect to a direct band gap is found at 7% tensile strain. A maximum spin splitting of 34.7 meV at the K′ valley is produced simultaneously with valley polarization under a tensile strain of 10%. The spin components distributed at the TVB are found to be controlled by strain-related competition between direct exchange interaction and indirect superexchange interaction of Se (px  +  py ) and Se pz orbitals. Spin polarization precisely regulated by strain can facilitate the manipulation of valley and spin degrees of freedom in MnPSe3/CrBr3 heterostructures, which opens up great potential for novel applications, such as strained sensor, spintronic and valleytronic devices. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a three-axis atomic magnetometer based on parametric oscillations, which can measure the three magnetic field components simultaneously and independently. A circularly polarized pump beam is applied to create the spin polarization, and another linearly polarized probe beam is used to detect the dynamics of the polarized spin under a magnetic field. With a closed-loop system to keep the magnetic field in resonance with the atoms, three components of magnetic field are measured by their feedback signals. We achieve a magnetometer sensitivity of 6 pT ()−1, 25 pT ()−1, and 60 pT ()−1 along three axes in the frequency range from 100 Hz to 1 kHz with a bandwidth better than 1 kHz under an unshielded environment. Furthermore, this magnetometer is free of optical modulation, which reduces the complexity of experimental setups. The methods we present here provide a prototype all-electrical three-axis atomic magnetometer. [ABSTRACT FROM AUTHOR]

In this study, we investigated the influence of the pump beam on the electronic and nuclear spin polarization homogeneity in the nuclear magnetic resonance gyroscope (NMRG). An analysis method was proposed based on the three dimensional simulation of the spin polarization spatial distribution. The pump power loss due to the aperture on the structure was considered. The average spin polarization and inertia measurement sensitivity were measured experimentally to demonstrate the simulation results. The results indicate that the nuclear spin polarization retains good homogeneity at different beam diameters, while the homogeneity of the electronic spin polarization highly depends on the beam diameter. It also can be seen that the electronic spin polarization homogeneity is more sensitive to pump power than pump beam diameter, while the nuclear spin polarization homogeneity is more sensitive to pump beam diameter than pump power. Moreover, the optimized beam diameter is obtained to balance the polarization and its homogeneity. The study provides reference for the design of the pump beam diameter and beam shaping structure in NMRG. [ABSTRACT FROM AUTHOR]

We investigate the Andreev reflections in a single-dot quantum ring with one s-wave superconductor side-coupled to the quantum dot, by considering the presence of local Rashba interaction and magnetic flux. It shows that in this system, the local Rashba interaction induces apparent spin polarizations of the local Andreev reflections, with their directions depending on the Rashba interaction and the lead index, respectively. Nevertheless, the crossed Andreev reflection cannot be polarized, and its magnitude can be adjusted by the threaded local magnetic flux. We propose this structure to be the promising candidate for achieving the manipulation of Andreev reflections. [ABSTRACT FROM AUTHOR]

Employing ab initio electronic structure calculations, we study a new class of magnetic Heusler compounds, which consist only of 3d transition metal atoms, namely, Fe2CrZ and Co2CrZ, where Z is an early 3d-metal, such as Sc, Ti or V. Although these compounds show a pseudogap and high spin polarization at the Fermi level, the so-called Slater–Pauling rule is not applicable to them. Co2CrTi and Co2CrV compounds present robust magnetic properties due to the short range magnetic exchange interactions and, thus, relatively high values of Curie temperature far above the room temperature. Moreover, these two compounds keep their magnetic properties upon B2 disorder that makes them very promising materials for spintronic and magnetoelectronic applications. [ABSTRACT FROM AUTHOR]

Electric field control of magnetization allows further miniaturization of integrated circuits for binary bit processing and data storage as it eliminates the need for bulky sophisticated systems to induce magnetic fields. Magnetoelectric coupling inherent to the bulk of multiferroic films or control of spin orientation in magnetic layers via piezoelectric strain in dual component composites have been two approaches standing out. Another magnetoelectric effect is spin-dependent screening that occurs at dielectric/ferromagnet interfaces which is of great importance for spin selective tunnel junctions. Here, we analyze the spin-dependent screening of ferroelectric polarization in a film interfacing ferromagnetic electrodes using the continuity equations in continuum media. The competition between the electrostatic and the magnetochemical potential in the FM electrodes gives rise to a reduction in the net magnetic moment near the interface due to spin mixing, extending to a distance comparable to the Thomas–Fermi screening length. Our continuum media treatment shows that the local spin population in spin subbands near the interfaces can dramatically deviate from bulk, which is in qualitative agreement with recent first principles results. We compute the tunneling currents for the majority and minority spins using the Wentzel–Kramers–Brillouin approximation as a function of ferroelectric polarization. We find that the spin polarization tends to disappear for increasing values of ferroelectric polarization in direct connection with the increase in subband spin population for minority spins at the interface. [ABSTRACT FROM AUTHOR]