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A mesoscopic multi-terminal superconducting Nb strip with a spin injection terminal has been developed. We investigate the influence of the spin polarization on the relaxation process of the quasiparticle in the superconducting Nb. The position dependence of the nonlocal voltage provides the quasiparticle relaxation length. The relaxation length for the spin-polarized quasiparticle is found to show 12.5 percent increase from that for the un-polarized quasiparticle. This demonstration opens a new avenue for utilization of the the spin current in a superconducting device.

Summary The photomagnetic effect is known to be related only to transition metal atoms with empty orbitals and spin-state changes. In general, noble metals with high electron density cannot be used as photomagnetic materials because of the absence of spin polarization. However, here, we found that photomagnetic-chiral anisotropy (PM-ChA) was generated in chiral nanostructured Au films (CNAFs), and opposite photomagnetic fields (PMFs) were created in the antipodal CNAFs under unpolarized irradiation. The PM-ChA was speculated to arise from directional alignment of opposite spins polarized by the asymmetric spin-orbit coupling due to the opposite effective magnetic fields induced by electron motion in the antipodal helical structure. PM-ChA can be applied in enantiomeric quantification, probably because of the spin polarization coupling between CNAFs and enantiomers. PM-ChA of noble metals generated by directional spin control in helical nanostructures could provide new strategies in quantum technology and theories in magnetophysics.

This article introduces and develop a new area of transparent conducting material by doping GaN with two rare earth (RE) impurities (Eu, Sm). Our theoretical calculations confirm that the co-doped compound exhibits half-metallic ferromagnet (HMF) with 100% spin polarization at the Fermi level using GGA and mBJ. To determine which magnetic configuration is the most stable one, we compared the energy of ferromagnetic and antiferromagnetic states. Our results suggest that the ferromagnetic state is the most stable ground state. The exchange splitting energy and exchange constants $$N_{0} \alpha$$ and $$N_{0} \beta$$ are calculated. Additionally, we determined the electron specific heat ‘c’. It has a high optical transmittance and conductivity. These properties make GaN doped with double rare-earth impurities a potential material in optoelectronic and solar cell applications. For the calculations of mechanical, optical, and transport properties, the generalized gradient approximation + Hubbard U (GGA + U) and the modified Becke–Johnson (GGA-TB-mBJ) approximations were used.

Out-of-plane spin polarization {\sigma}_z has attracted increasing interests of researchers recently, due to its potential in high-density and low-power spintronic devices. Noncollinear antiferromagnet (AFM), which has unique 120{\deg} triangular spin configuration, has been discovered to possess {\sigma}_z. However, the physical origin of {\sigma}_z in noncollinear AFM is still not clear, and the external magnetic field-free switching of perpendicular magnetic layer using the corresponding {\sigma}_z has not been reported yet. Here, we use the cluster magnetic octupole in antiperovskite AFM Mn3SnN to demonstrate the generation of {\sigma}_z. {\sigma}_z is induced by the precession of carrier spins when currents flow through the cluster magnetic octupole, which also relies on the direction of the cluster magnetic octupole in conjunction with the applied current. With the aid of {\sigma}_z, current induced spin-orbit torque (SOT) switching of adjacent perpendicular ferromagnet is realized without external magnetic field. Our findings present a new perspective to the generation of out-of-plane spin polarizations via noncollinear AFM spin structure, and provide a potential path to realize ultrafast high-density applications., Comment: 23 pages, 4 figures, accepted by Nat. Commun

Spin-dependent charge transmission or the so-called chirality-induced spin selectivity (CISS) effect was demonstrated in self-assembled chiral coordinated monolayers. Distinct from the previous CISS phenomenon observed mainly on pure biomolecules, here we expanded this effect to the coordinated complex of chiral biomolecules and metal cations, specifically, cysteine-Cu2+-alanine (Cys/Cu/Ala), in which the complex itself was redox-active. However, the coordinated self-assembled monolayers of cysteine-Cu2+-cysteine did not show any spin-dependent effect. In addition, this phenomenon was explained by developing a theoretical model with spin-orbit coupling. The alanine molecules contributed to multiple transport pathways, leading to experimentally observable spin polarization. Finally, this CISS effect in Cys/Cu/Ala complex was demonstrated to amplify the sensing signal. The enantioselective discrimination efficiency could be improved by controlling the orientation of the external magnetic field.

In this article, for the first time, we propose a silicene-based spin filter having a TFET configuration. The device portrays a voltage-dependent spin polarization and achieves a “spin polarization” as high as 98% at a minimal “operating voltage” (0.35 V). The operation of the device is based on the “spin-polarized edge states” in a silicene nanoribbon. The “spin polarization” of the output current can be tuned by modifying the bandgap of the spin-up and spin-down states via an in-plane perpendicular “electric field” generated by two “lateral gates.” The device features high spin polarization apart from its expected integration with Si-based technology. The proposed device has a simple construction, wherein a single layer of Si atoms achieves such a high value of spin polarization at a minimal operating voltage. The operation of the proposed device is demonstrated by using the first-principles quantum transport simulations.

The mechanism of spin polarization transfer from a photogenerated spin-correlated radical pair to a stable radical was studied in a covalent donor-chromophore-acceptor-stable radical (D-C-A-R•) system, where the donor (D) is 4-methoxyaniline (MeOAn), the chromophore (C) is 4-(N-piperidinyl)-naphthalene-1,8-dicarboximide (ANI), the acceptor (A) is naphthalene-1,8:4,5-bis(dicarboximide) (NDI) and the stable radical (R•) is (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO). Experiments probed the effect of the spin–spin exchange interaction between D•+ and A•− as well as the charge recombination dynamics of D•+-C-A•− on spin polarization transfer from the D•+-C-A•− SCRP to R• as a function of the dielectric environment in glassy media at cryogenic temperatures. The results show that spin polarization on R• is generated by asymmetry in the charge recombination pathways rather than variations in the spin–spin exchange interaction between D•+ and A•−. These results inform design criteria for using an SCRP to spin polarize a third spin for potential applications in quantum information science.

A new scheme is presented for obtaining a pure spin state for the one-determinant wave function built on Hartree–Fock or Kohn–Sham orbitals. In this scheme, the unrestricted determinant is expanded in restricted determinants constructed in the basis set of spin-paired orbitals. Using spin projection, one can determine spin density components corresponding to pure spin states and estimate the weight of spin contaminants in the spin density. The efficiency of this approach is demonstrated on the example of methane oxidation. It is shown that self-consistent solutions of Hartree–Fock or Kohn–Sham equations with broken spin symmetry are not an artifact of one-determinant approximation. The equations reflect real spin polarization that creates negative spin density in some parts of the molecular system.

The quaternary Heusler LuCoTiSi, LuCoTiGe, and LuCoTiSn compounds' physical properties have been investigated using the GGA approximation based on the density functional theory. These compounds are stable in the ferromagnetic phase and semi-stable in the non-magnetic phase. Elastic studies show that these compounds are quite stable and belong to the category of ductile materials. Phonon calculations also show that these two combinations are quite stable, and the phonon levels in the band structure are all in the positive region. The LuCoTiSi, LuCoTiGe, and LuCoTiSn compounds are half-metallic with 100% spin polarization with 2.0µB 3.0 µB, and 2.0µB, respectively. The maximum value of their Seebeck (S) coefficient occurred at 130 K. The figure of merit (ZT) coefficient of these compounds at 100 K equals one and decreased to room temperature with a gentle slope, indicating their thermoelectric efficiency at low and room temperatures. All compounds have accessible regions that referred to their thermodynamic stability. The LuCoTiGe case has a more extensive accessible region than other cases of the thermodynamic phase diagram.

Electric field control of magnetic properties has been achieved across a number of different material systems. In diluted magnetic semiconductors (DMSs), ferromagnetic metals, multiferroics, etc., electrical manipulation of magnetism has been observed. Here, we study the effect of an electric field on the carrier spin polarization in DMSs ( GaAsMn ); in particular, emphasis is given to spin-dependent transport phenomena. In our system, the interaction between the carriers and the localized spins in the presence of electric field is taken as the main interaction. Our results show that the electric field plays a major role on the spin polarization of carriers in the system. This is important for spintronics application.

Molecular spintronics may boost the development of nanoscale devices with improved performance and enhanced functionality, which is very promising for the next generation of electronic devices. Here, we design a new type of spintronics device based on the novel 2D material C3N. Using nonequilibrium Green’s function in combination with the density functional theory, we systematically study the spin-dependent transport properties in four different magnetic configurations of the C3N junction, and the perfect spin filter efficiency and giant magnetoresistance effects are achieved. The calculated results clearly demonstrate that the transport properties of the C3N junction are sensitive to the magnetic configuration of the electrodes. The calculated spin-resolved transmission spectra of the proposed ferromagnetic coupling C3N junctions exhibit a robust spin filtering effect, where the conductance is mainly governed by the spin-down electrons. Under the small bias voltage, the transport properties are mainly determined by the spin-down channel and exhibit a large spin polarization. The conductance of three antiferromagnetic coupling states is nearly zero at the Fermi level. These theoretical results indicate that the novel 2D C3N monolayer is promising for molecular spintronics devices in the near future.

We theoretically investigate the dwell time for electrons in an antiparallel double $\delta $ -magnetic-barrier nanostructure, which is constructed on the surface of the InAs/Al x In1- x As heterostructure by patterning two ferromagnetic (FM) stripes. It is shown that the dwell time is dependent on electron spins due to the spin–field interaction between spins and magnetic fields. It is also shown that both magnitude and sign of the spin polarization in the dwell time can be modulated by the structural width or magnetic-strength difference between two magnetic barriers, which may give rise to a controllable temporal spin splitter for spintronics device applications.

Non-stationary spin-dependent transport through the interacting single-level quantum dot coupled to ferromagnetic leads with non-collinear magnetizations has been analyzed theoretically. The non-stationary transport is investigated within the theoretical approach based on kinetic equations for the electron occupation numbers with different spins taking into account high order correlation functions for the localized electrons. It has been demonstrated that spin polarization, direction and amplitude of the non-stationary currents could be effectively changed in a rather simple system by varying the relative directions of the magnetic moments in the leads. The degree of the currents spin polarization also changes following the direction of magnetic moments in the leads. The results open a possibility for spin polarization control in nanoscale systems and are very promising in the sense of spin filtering.

Nuclear magnetic resonance (NMR) spectroscopy is a powerful method to study the molecular structure and dynamics of materials. The inherently low sensitivity of NMR spectroscopy is a consequence of low spin polarization. Hyperpolarization of a spin ensemble is defined as a population difference between spin states that far exceeds what is expected from the Boltzmann distribution for a given temperature. Dynamic nuclear polarization (DNP) can overcome the relatively low sensitivity of NMR spectroscopy by using a paramagnetic matrix to hyperpolarize a nuclear spin ensemble. Application of DNP to NMR can result in sensitivity gains of up to four orders of magnitude compared to NMR without DNP. Although DNP NMR is now more routinely utilized for solid-state (ss) NMR spectroscopy, it has not been exploited to the same degree for liquid-state samples. This Review will consider challenges and advances in the application of DNP NMR to liquid-state samples. The Review is organized into four sections: (i) mechanisms of DNP NMR relevant to hyperpolarization of liquid samples; (ii) applications of liquid-state DNP NMR; (iii) available detection schemes for liquid-state samples; and (iv) instrumental challenges and outlook for liquid-state DNP NMR.

To broaden the scope of van der Waals 2D magnets, we report the synthesis and magnetism of covalent 2D magnetic Cr$_2$Te$_3$ with a thickness down to one-unit-cell. The 2D Cr$_2$Te$_3$ crystals exhibit robust ferromagnetism with a Curie temperature of 180 K, a large perpendicular anisotropy of 7*105 J m-3, and a high coercivity of ~ 4.6 kG at 20 K. First-principles calculations further show a transition from canted to collinear ferromagnetism, a transition from perpendicular to in-plane anisotropy, and emergent half-metallic behavior in atomically-thin Cr$_2$Te$_3$, suggesting its potential application for injecting carriers with high spin polarization into spintronic devices.

The spin resonance of two-dimensional conduction electrons in a ZnO/MgZnO heterojunction in tilted magnetic fields is studied near the filling factor $$\nu = 2$$ . The analysis of the spin resonance intensity at various ν values indicates that a phase transition accompanied by drastic change in the spin polarization occurs in a two-dimensional electron system at a certain angle near $$\nu = 2$$ . For ν values larger than a certain critical value νc, an intense spin resonance is observed, clearly demonstrating that the system turns out to be in a spin-polarized state. For ν < νc, the resonance amplitude drops by more than an order of magnitude, and the spin polarization of the ground state decreases significantly. In the immediate vicinity of the transition, the spin resonance is broadened significantly and split into several independent peaks. Such behavior of the resonance can most likely be explained by the division of the system into domains with different spin polarizations.

In non-centrosymmetric metals, spin-orbit coupling (SOC) induces momentum-dependent spin polarization at the Fermi surfaces. This is exemplified by the valley-contrasting spin polarization in monolayer transition metal dichalcogenides (TMDCs) with in-plane inversion asymmetry. However, the valley configuration of massive Dirac fermions in TMDCs is fixed by the graphene-like structure, which limits the variety of spin-valley coupling. Here, we show that the layered polar metal BaMn$X_2$ ($X =$Bi, Sb) hosts tunable spin-valley-coupled Dirac fermions, which originate from the distorted $X$ square net with in-plane lattice polarization. We found that in spite of the larger SOC, BaMnBi$_2$ has approximately one-tenth the lattice distortion of BaMnSb$_2$, from which a different configuration of spin-polarized Dirac valleys is theoretically predicted. This was experimentally observed as a clear difference in the Shubnikov-de Haas oscillation at high fields between the two materials. The chemically tunable spin-valley coupling in BaMn$X_2$ makes it a promising material for various spin-valleytronic devices., Comment: 25 pages, 4 figures. Published in Communications Materials

The influence of spatial variation of Fermi velocity on the spin-polarized transport properties of massless Dirac fermions in proximity-induced ferromagnetic graphene junction was investigated. We found that the velocity ratio ξ causing the width of the spin conductance dip near the Dirac point is broadened as the Fermi velocity ratio increases. In contrast, the effect of the Fermi velocity mismatch does not affect the shifting of the Dirac point. It leads to the indirect measurement of the Fermi velocity ratio that can be tuned by the spin-dependent conductance. In addition to the presence of both the exchange field and the Fermi velocity modulation, we found high spin filtering occurs when the Fermi velocity ratio ξ ≥ 1. Due to the transmission probability of electron with spin down, T↓ is blocked by the effect of Fermi velocity modulation similar to waves travelling through a different media. Moreover, we also found that the resonant transmission of the electron with spin up can be perfectly transmitted through the Fermi velocity barrier at the limit injected angle θ → π/2 for H/EF ≈ 1. The spin transport properties can be controlled by suitably modifying the strength of the ferromagnetic insulator and varying the Fermi velocity modulation, which leads to the highest spin polarization. By manipulating the behavior of spin-dependent collimation and spin beam splitting in this structure, we proposed a spin transport device for making lateral spin polarization. These interesting features will help make the development of spintronic devices in the graphene-based nanostructure.

Based on the full-potential linearized augmented plane wave (FP-LAPW) method, we have investigated the electronic, structural, magnetic and optical properties of Cd0.9375TM0.0625S (TM = Mn, Fe, Co and Ni) compounds in the zinc-blende (ZB) ferromagnetic phase. The magnetic and electronic properties are treated using the PBE-GGA and TB-mBJ approximations. CdS is well known as a non-magnetic semiconductor. When CdS is doped with a transition metal (TM), Cd0.9375TM0.0625S (TM = Mn, Fe, Co) changes to half-semiconductors (HSC) and Cd0.9375Ni0.0625S to a half-metal (HM). It is found that the 3d-t2g states of the transition metal are responsible for generating spin polarization and magnetic moment in these compounds. All the considered compounds are ferromagnetic and the calculated total magnetic moment increases from 2 to 5 µB moving from Ni to Mn. The optical properties exhibited new peaks in the visible and ultraviolet regions due to the effect of free-carrier absorption related to the magnetic impurities. Our results show very good agreement to previous theoretical and experimental data. The results presented herein imply that TM-doped CdS has potential for applications in spintronic and optoelectronic device sectors in a wide energy range of the light spectrum from visible to ultraviolet.

Spin-polarized currents are investigated in symmetric (asymmetric) resonant magnetic tunnel junctions (S- (A)-RMTJs) including a non-magnetic metal (NM) layer. Charge-diode and spin-diode features are found for the S-RMTJs at definite thicknesses of MgO and NM layers. Owing to the presence of quantum-well states, a full spin polarization can be achieved by proper choice of the thickness of NM layer. The charge and spin currents have increased for the A-RMTJs in comparison to those of the S-RMTJs due to different properties of ferromagnetic electrodes. The present study suggests new spin-filter devices to use in the spintronics field.

In this paper, an ab initio study of the electronic and magnetic properties of CdS doped by the transition metal elements has been investigated. Based on the KKR-CPA method within the Generalized Gradient Approximation (GGA), we have calculated the total energy to determine the most stable state in the system and found it to be the ferromagnetic state for Ti, V and Cr-doped CdS, while it is the stabilization in spin glass states for Mn and Co cases. On the other hand, we have investigated and plotted the density of states (DOSs) which reveals that the doped compounds exhibit a half-metallic character. The spin polarization at Fermi level is estimated and found to be around 100%. Furthermore, we have identified the type of mechanism of exchange interactions being double exchange for all components except Mn case where we find that the responsible mechanism is the p-d exchange. The evaluation of the Curie temperature variation TC for the three components stable in the ferromagnetic phase revealed values greater than 300 K for most cases. The effect of the crystal field and the exchange splitting as a function of the concentrations values has been also investigated. Half-metallic substances are very interesting for spin-dependent electronics devices as they boost their magnetoresistance capacity.

An exclusive advantage of semiconductor spintronics is its potential for opto-spintronics, which will allow integration of spin-based information processing/storage with photon-based information transfer/communications. Unfortunately, progress has so far been severely hampered by the failure to generate nearly fully spin-polarized charge carriers in semiconductors at room temperature. Here we demonstrate successful generation of conduction electron spin polarization exceeding 90% at room temperature without a magnetic field in a non-magnetic all-semiconductor nanostructure, which remains high even up to 110 degrees C. This is accomplished by remote spin filtering of InAs quantum-dot electrons via an adjacent tunnelling-coupled GaNAs spin filter. We further show that the quantum-dot electron spin can be remotely manipulated by spin control in the adjacent spin filter, paving the way for remote spin encoding and writing of quantum memory as well as for remote spin control of spin-photon interfaces. This work demonstrates the feasibility to implement opto-spintronic functionality in common semiconductor nanostructures. An electron spin polarization of 90% is achieved in a non-magnetic nanostructure at room temperature without magnetic field. This is accomplished by remote spin filtering of InAs quantum-dot electrons via an adjacent tunnelling-coupled GaNAs spin filter. Funding Agencies|Swedish Research CouncilSwedish Research CouncilEuropean Commission [2015-05532, 2019-04312, 201605091, 2020-04530]; Swedish Foundation for International Cooperation in Research and Higher Education (STINT) [JA2014-5698]; Linkoping University; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; European Research Council, ERC AdG AMETISTEuropean Research Council (ERC) [695116]; Academy of FinlandAcademy of FinlandEuropean Commission [310985, 323989]; Japan Society for the Promotion of Science (JSPS)Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science [16H06359, 19H05507]; JSPSMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science [19K15380]

The electronic and magnetic properties of armchair-hexagonal (AHEX) and zigzag-triangular (ZTRI) graphene quantum dots doped with alkali metals are investigated using density functional theory. The binding energy confirms the stability of the undoped systems. Although doping decreases stability of single layer structures, in bilayer ones the binding energy between the layers increases. The former is due to the broken bonds and the deformation at the surface, while the later is due to the chemical bonds formation between the layers. We found that the lowest ground state energy for AHEX/AHEX-doped is the singlet/quadruplet spin state. Therefore, AHEX dots experience transformation from diamagnetic to ferromagnetic state after doping. In addition, the optimized spin state for ZTRI/ZTRI-doped is the quintet/sextet spin-polarized state. In few cases, the doped AHEX/ZTRI dots have doublet/quadruplet spin state due to the strong interaction between the flake atoms that passivates some unpaired electrons. Magnetic properties depend also on stacking, for instance pristine bilayer triangular flakes become antiferromagnetic due to pairing between edge states. The energy gap significantly affected by doping, for instance the gap decreases from ~3.7 eV in hexagonal flakes to 1.5 eV when it is doped with Na in the upper position. Electrons from the broken bonds around the doped metal form orbitals loosely bound to the flake consequently decreasing the energy gap. On the other hand, stacking increases the energy gap in bilayer triangular flakes due to the mutual passivation of the reactive edge states from both the layers. The calculated spin up/down density ratio is high in hexagonal flakes leading to high spin polarization (P), for instance P = 0.64 in hexagonal flakes doped with K atom. The found enhanced spin polarization, in addition to the tunable magnetic properties, makes doped graphene flakes promising candidates for spintronic devices.

The high degree of spin-polarization observed in ordered double perovskite oxide Sr2FeMoO6 at room temperature has attracted considerable interest from both fundamental and practical points of view...

Topological aspects of the geometry of DNA and similar chiral molecules have received a lot of attention, while the topology of their electronic structure is less explored. Previous experiments have revealed that DNA can efficiently filter spin-polarized electrons between metal contacts, a process called chiral-induced spin-selectivity (CISS). However, the underlying correlation between chiral structure and electronic spin remains elusive. In this work, we reveal an orbital texture in the band structure, a topological characteristic induced by the chirality. We find that this orbital texture enables the chiral molecule to polarize the quantum orbital. This orbital polarization effect (OPE) induces spin polarization assisted by the spin-orbit interaction from a metal contact and leads to magnetorestistance and chiral separation. The orbital angular momentum of photoelectrons also plays an essential role in related photoemission experiments. Beyond CISS, we predict that OPE can induce spin-selective phenomena even in achiral but inversion-breaking materials., Comment: 24 pages, 4 figures, and Supplementary Materials

The present work reports the magnetism analysis of zigzag and armchair forms of CuO nanoribbons by using density functional theory (DFT)-based ab initio approach. The structural stability has been confirmed through the binding energy calculation. The electronic and magnetic properties have been analyzed as a function of varied width of CuO nanoribbons, interesting information for variety of applications. The metallic and ferromagnetic behaviors of CuO nanoribbons are observed, whereas its bulk counterpart shows a p-type semiconducting and antiferromagnetic nature. The computed magnetic moments for the zigzag and armchair forms of CuO nanoribbon are in the ranges of 0.19–0.61 μB and 0.24–0.97 μB, respectively. The computed spin polarizations confirms the half or full metallic ferromagnetic nature of these nanoribbons.

Spin polarization in the electron transmission of radicals is important for understanding single-molecule conductance experiments focusing on shot noise, Kondo properties or magnetoresistance. We study how stable radical substituents can affect such spin polarization when attached to oligo(p- phenyleneethynylene) (OPE) backbones. We find that it is not straightforward to translate the spin density on a stable radical substituent into spin-dependent transmission for the para-connected wires under study here, owing to increased steric interactions compared with meta-connected wires, and a resulting twisting of the radical substituent and OPE π systems. The most promising example is a t-butyl nitroxide substituent, which, despite little pronounced spin delocalization onto the backbone, yields a spin-dependent transmission feature which one might be able to shift towards the Fermi energy by additional substituents. We also find that for bulkier substituents, dispersion interactions with the substituent can lead to twisting of one of the outer OPE rings, reducing the overall conductance. As a further potential design consideration, attaching radicals via linkers might increase the possibilities for spin-dependent intermolecular and molecule-electrode interactions.

This paper theoretically examines the spin-dependent transport of electrons through InAs/GaAs symmetric triple barriers by solving the spin-dependent Schrodinger equation. The Transfer Matrix Method (TMM) was used to investigate the impact of the hydrostatic pressure, temperature, and magnetic field on the transmission coefficient and spin polarization of electrons while taking into account the Rashba and Dresselhaus spin orbit interactions. The results indicate that when both the hydrostatic pressure and temperature increase, the two resonant states of spin-up and down electrons move toward lower energies (blue shift). In addition, when the magnitude of the applied magnetic field increases, the resonant states of spin-up electrons shift toward lower energies, whereas the spin-down ones shift toward higher energies, which leads to perfect spin separation. This important spin-separation behavior could be very useful in the design of spin filters, which are strongly required in spintronics applications.

Due to the gapless between any two successive subbands with the same spin, the spin polarization in uniform MoS2 zigzag nanoribbon (MoS2-ZR) is weak. Here, through configuring Z-shaped structure, we realize 100% spin polarization in MoS2-ZR with only exchange field. The filtered spin electrons transmit along a specified edge of the device. This phenomenon is the result of the combined effect of the localized edge states and structure induced inversion of the Mo-edge and S-edge. In our calculation the fully spin polarization appears in several energy regions, so this Z-shaped MoS2-ZRs can be used in making spintronic devices.

The spin-dependent Seebeck effect (SDSE) and thermal spin-filtering effect (SFE) are now considered as the essential aspects of the spin caloritronics, which can efficiently explore the relationships between the spin and heat transport in the materials. However, there is still a challenge to get a thermally-induced spin current with no thermal electron current. This paper aims to numerically investigate the spin-dependent transport properties in hybrid graphene/silicene nanoribbons (GSNRs), using the nonequilibrium Green’s function method. The effects of temperature gradient between the left and right leads, the ferromagnetic exchange field, and the local external electric fields are also included. The results showed that the spin-up and spin-down currents are produced and flow in opposite directions with almost equal magnitudes. This evidently shows that the carrier transport is dominated by the thermal spin current, whereas the thermal electron current is almost disappeared. A pure thermal spin current with the finite threshold temperatures can be obtained by modulating the temperature, and a negative differential thermoelectric resistance is obtained for the thermal electron current. A nearly zero charge thermopower is also obtained, which further demonstrates the emergence of the SDSE. The response of the hybrid system is then varied by changing the magnitudes of the ferromagnetic exchange field and local external electric fields. Thus, a nearly perfect SFE can be observed at room temperature, whereas the spin polarization efficiency is reached up to 99%. It is believed that the results obtained from this study can be useful to well understand the inspiring thermospin phenomena, and to enhance the spin caloritronics material with lower energy consumption.

Manganites have shown potential in spintronics because they exhibit high spin polarization. Here, by ferromagnetic resonance we have studied the damping properties of La0.67Sr0.33MnO3/Pt bilayers which are prepared by oxide molecular beam epitaxy. The damping coefficient (α) of a La0.67Sr0.33MnO3 (LSMO) single layer is found to be 0.0104. However the LSMO/Pt bilayers exhibit a decrease in α with an increase in Pt thickness. This decrease in the value of α is probably due to high anti-damping like torque. Furthermore, we have investigated the angle dependent inverse spin Hall effect (ISHE) to quantify the spin pumping voltage from other spin rectification effects such as the anomalous Hall effect and anisotropic magnetoresistance. We have observed a high spin pumping voltage (∼20 μV). The results indicate that both anti-damping and spin pumping phenomena occur simultaneously.

Exploring the manipulation of magnetism in perovskite oxides is scientifically interesting and of great technical importance in next-generation magnetic memory. Dual control of magnetism in superlattices through epitaxial strain and ferroelectric polarization may induce rich physical properties. In this work, we demonstrated a strong magnetoelectric coupling that appears in an La0.75Sr0.25MnO3/BaTiO3 superlattice. Reversible transitions in ferromagnetism, ferrimagnetism and anti-ferromagnetism, with strong magnetoelectric coupling, are achieved by precisely controlling the magnitude and spin-direction of the magnetic moments of Mn. Half-metallicity is demonstrated in the MnO2 layers, accompanied by the spin polarization of the superlattice varying from 100% to 0%. We realize the coexistence of ferroelectric polarization and metallicity, i.e., "ferroelectric metal". The variation in strain and re-orientation of polarization lead to a change in interfacial Ti-O and Mn-O bond lengths, and hence a hybridization state, determining the magnetism of our system. The purpose-designed LSMO/BTO superlattice with intrinsic magnetoelectric coupling is a particularly interesting model system that can provide guidance for the development of spintronic devices.

We have investigated the half metallic Heusler alloy, Co2TiSi via first principle calculation using the Wien2K code and studied the electronic, magnetic and optical properties. Density of state (DOS) profile represents the half metallic character for Co2TiSi i.e, 100% spin polarization at the Fermi level. Partial (p-) DOS show that major contribution is due to Co-3d and Ti-3d states across the Fermi level. Band structure also shows a band gap of ~ 1.0 eV for spin down states whereas metallic character for the spin up states. Calculated electronic and magnetic behavior along with estimated magnetic moment (1.98 μB) found to be in good agreement with its experimental results.

We investigate spin dependent electron transport through a magnetic helix (MH) which is coupled to one input and two output leads. Suitably adjusting the physical parameters and lead positions we can achieve high degree of spin polarizations with opposite phase at the output terminals. We consider both long-range and short-range hopping magnetic helices and critically examine the interplay between these hopping integrals on spin polarization. From our results we find that the long-range hopping MH is much superior than the short-range one. Simulating the quantum system within a tight-binding framework we compute spin dependent transmission probabilities and spin polarization co-efficient using the well known Green’s function formalism. Our proposition can provide a deeper impact in realizing efficient spin based devices in near future.

Nodal-ring semimetals with band crossing are the new type of quantum materials that have attracted considerable interest from scholars for research. In general, the spin–orbit coupling (SOC) effect opens a band gap at the Dirac point. Therefore, finding 2D nodal-ring semimetals with resistance to SOC has more challenges. Based on first-principles calculations, we propose here that the two-dimensional (2D) Ta2C3 monolayer is a novel nodal-ring semimetal. In particular, Ta2C3 forms six closed rings in the Brillouin zone (BZ) with SOC, which originates from the dxy,x2–y2 orbitals of Ta and the pz orbitals of C. The nodal-ring bands at the K point in Ta2C3 exhibits characteristics of valley splitting and spin polarization due to the breaking of inversion symmetry and SOC. The masximal spin-splitting at the K point is as large as 268.87 meV and 61.90 meV for the conduction band minimum (CBM) and valence band maximum (VBM), respectively. The massless Dirac fermions in the non-equivalent valley have the opposite Berry curvature and spin moment. Therefore, 2D Ta2C3 is novel spin-valley-coupled nodal-ring semimetal. In addition, we found interesting negative differential resistance effects when calculating its transport properties. Our results not only provide an ideal platform for studying the combination of new physical properties, spintronics and valleytronics, but also open the way for designing low-power and fast-transport electronic devices.

Novel spintronic devices with low power consumption, nonvolatility, and high storage density are highly desired to meet the rapid development of modern information storage and communication technology, which poses a great challenge to both material and device researches. To overcome this challenge, our group has focused our research on the following two aspects. On one hand, we have explored novel magnetoresistance effects in a variety of materials and devices, aiming to get a deep understanding about the spin dependent transport and obtain an effective control of spin-dependent transport. On the other hand, we have tried to control the magnetoresistance based on multi-physical field effects, aiming to obtain spintronic prototype devices that can be used for multi-state data storage. Regarding the novel magnetoresistance explorations, this article will introduce: (1) The negative magnetoresistance in amorphous condensed magnetic semiconductors. The spin dependent variable range hopping model is proposed, which can quantitatively explain the temperature and magnetic field dependent transport behavior in the condensed magnetic semiconductors. In addition, this model provides an alternative way to detect the spin polarization ratio of the magnetic semiconductors. (2) The positive magnetoresistance in single-crystal CoZnO magnetic semiconductors. By quantitative analysis of the transport properties of CoZnO films, it is observed that the positive magnetoresistance in the “hard gap” regime is the result of the carrier wavefunction shrinkage under applied magnetic field. (3) The rectification magnetoresistance in non-magnetic Schottky heterojunctions and the tunneling rectification magnetoresistance in magnetic tunnel junctions. A brand new rectification magnetoresistance is observed in nonmagnetic Al/Ge Schottky heterojunctions: The application of a pure small sinusoidal alternating current to the nonmagnetic Schottky heterojunctions can generate a significant direct-current voltage, and this rectification voltage strongly varies with the external magnetic field. Moreover, by using CoO-ZnO composite tunneling barrier, the charge-related rectification and spin-dependent tunneling magnetoresistance are integrated into the Co/CoO-ZnO/Co magnetic tunneling junctions to realize the tunneling rectification magnetoresistance. The observation of rectification magnetoresistance and tunneling rectification magnetoresistance not only adds new members to the magnetoresistance family, but also provides a promising way to control the devices’ properties by using alternating current. In terms of multistate data storage application, this review will introduce: (1) The electrical and magnetic field controllable 4 resistance states in oxide heterojunctions. In Co/CoO-ZnO/Co magnetic tunneling junctions, by integrating the electrical field induced resistance switching and the magnetic field induced tunneling magnetoresistance effects, four nonvolatile resistance states are demonstrated. (2) The remanent magnetization controllable 10 resistance states in magnetic heterojunctions. Here, a general remanent magnetism engineering method is proposed for realizing multiple reliable magnetic and resistance states, not depending on a specific material or device structure. Especially, as a proof-of-concept demonstration, ten states of nonvolatile memory based on the manipulation of ferromagnetic remanent magnetization have been revealed in both Co/Pt magnetic multilayers with strong perpendicular magnetic anisotropy and MgO-based magnetic tunneling junctions at room temperature. (3) The spin-orbit torque controllable 10 resistance states in single-layer magnetic alloy. A repeatable bulk spin-orbit torque switching of the perpendicularly magnetized CoPt alloy single-layer films is realized by introducing a composition gradient in the thickness direction to break the inversion symmetry. Moreover, a ten states nonvolatile memory is illustrated solely by changing the electrical current to control the multi-domain states of the CoPt alloy.

In a semiconductor spin device with electrodes formed from the Fe2NbSn half-metallic ferromagnet film, a spin polarization of PS = 4% of electrons injected into the InSb semiconductor has been obtained. This corresponds to the maximum possible PS value for transparent contacts of a semiconductor and a ferromagnet, in which the polarization is PF = 95%. It is shown that, to ensure the effective injection of spin-polarized electrons from a ferromagnet into a semiconductor, it is necessary to use a ferromagnet with the 100% electron polarization or to form an additional high-resistance layer in the interface.

The structure, electrical transport, and magnetic properties have been systematically studied in superconducting Ti1−xMgxO (x = 0, 0.003, 0.02, 0.08, and 0.27) films. It is found that, both the zero resistance and onset superconducting transition temperatures of Ti1−xMgxO first increase with increasing the Mg content from x = 0 to x = 0.02, and then decrease with the further increase of x. More interestingly, the Mg-doping simultaneously introduces a ferromagnetic order into this superconducting system, and the ferromagnetism gradually increases with increasing Mg content. According to the first-principles calculations, the non-monotonous Mg doping-dependent superconductivity, carrier density, and disorder strength may be explained as that the Mg atoms first fill the Ti vacancy sites and then substitute the Ti atoms. The calculations also reveal that the ferromagnetism is highly related to the spin polarization of 3d states of Ti atoms surrounding Mg atoms. The discovery of enhanced superconductivity with coexisting ferromagnetism in Ti1−xMgxO films provides an excellent platform to investigate the interaction between superconductivity and ferromagnetism.

A single molecule offers to tailor and control the probing capability of a scanning tunneling microscope when placed on the tip. With the help of first-principles calculations, we show that on-tip spin sensitivity is possible through the Kondo ground state of a spin S = 1/2 cobaltocene molecule. When attached to the tip apex, we observe a reproducible Kondo resonance, which splits apart upon tuning the exchange coupling of cobaltocene to an iron atom on the surface. The spin-split Kondo resonance provides quantitative information on the exchange field and on the spin polarization of the iron atom. We also demonstrate that molecular vibrations cause the emergence of Kondo side peaks, which, unlike the Kondo resonance, are sensitive to cobaltocene adsorption., The authors thank the Agence Nationale de la Recherche (Grants ANR-13-BS10-0016, ANR-11-LABX-0058 NIE, and ANR-10-LABX-0026 CSC) and the MICINN (project RTI2018-097895–B-C44) for financial support.

Despite extensive research on recently discovered layered ferromagnetic (FM) materials, their further development is hampered by the limited number of candidate materials with desired properties. As a much bigger family, layered antiferromagnetic (AFM) materials represent excellent platforms to not only deepen our understanding of fundamental physics but also push forward high-performance spintronics applications. Here, by systematic first-principles calculations, we demonstrate pressure and carrier doping control of magnetic properties in layered AFM CoPS3, a representative of transition metal phosphorus trichalcogenides. In particular, pressure can drive isostructural Mott transition, in sharp contrast to other transition metal thiophosphates. Intriguingly, both pressure and carrier doping can realize the long-sought FM half-metallic states with 100% spin polarization percentage, which is good for improving the injection and detection efficiency of spin currents among others. Moreover, the Mott transition is accompanied by instantaneous spin-crossover (SCO) in CoPS3, and such cooperative SCO facilitates the implementation of fast-response reversible devices, such as data storage devices, optical displays and sensors. We further provide an in-depth analysis for the mechanisms of FM half-metallicity and SCO. Tunable magnetism in layered AFM materials opens vast opportunities for purposeful device design with various functionalities.

Based on the density functional theory framework and GGA approximation, the structural, electronic, optical and thermoelectric properties of the Co2TaAl and its [001] films have been calculated. The Co2TaAl compound has great hardness with the bulk modulus of 201.5 GPa which is bigger than steel. This compound has half-metallic nature with 100% spin polarization in the Fermi surface and 2.0µB magnetic moment. Due to its the real and imaginary dielectric function responses in the visible region and very low Eloss and extinction, this compound is a suitable case for optical applications in visible area energy. The Co2TaAl, also has a suitable thermoelectric efficiency in all temperatures, for a spin down with big power factor in high temperatures which is suitable for power generation applications. The energy-volume and thermodynamic phase diagrams of the [001] films are indicate, their stability, in the mechanical and thermodynamic views. The electronic diagrams showed the half-metallic behavior of the TaAl termination with 100% spin polarization, by the 0.25 eV energy gap in the down spin. The optical response of the TaAl termination for the E⊥z direction is similar to that of the bulk case and has a red shift, but in the E∥z the metallic nature is reduced. The merit amount of the TaAl termination is 0.7 in the lower temperatures for a down spin and its Seebeck has been greater than that of the bulk case.

The interconversion of charge and spin currents via spin-Hall effect is essential for spintronics. Energy-efficient and deterministic switching of magnetization can be achieved when spin polarizations of these spin currents are collinear with the magnetization. However, symmetry conditions generally restrict spin polarizations to be orthogonal to both the charge and spin flows. Spin polarizations can deviate from such direction in nonmagnetic materials only when the crystalline symmetry is reduced. Here, we show control of the spin polarization direction by using a non-collinear antiferromagnet Mn3GaN, in which the triangular spin structure creates a low magnetic symmetry while maintaining a high crystalline symmetry. We demonstrate that epitaxial Mn3GaN/permalloy heterostructures can generate unconventional spin-orbit torques at room temperature corresponding to out-of-plane and Dresselhaus-like spin polarizations which are forbidden in any sample with two-fold rotational symmetry. Our results demonstrate an approach based on spin-structure design for controlling spin-orbit torque, enabling high-efficient antiferromagnetic spintronics., In the typical spin-hall effect, spin-current, charge current, and spin polarisation are all mutually perpendicular, a feature enforced by symmetry. Here, using an anti-ferromagnet with a triangular spin structure, the authors demonstrate a spin-hall effect without a perpendicular spin alignment.

The half-Heusler ScPtBi compound, known with non-magnetic semi-metallic electronic behavior, mainly has topological properties in spin–orbit calculations. In the present study, the electronic structure and thermoelectric performance of this compound are studied under the substitution of vanadium, magnetic metal, instead of Sc atoms. Calculations were carried out in the framework of density functional theory (DFT) by applying Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) and corrected Tran and Blaha-modified Becke–Johnson potential (TB-mBJ) as well as solving Boltzmann semi-classical equations. The V atom’s entry leads to the change in the non-magnetic electronic structure of ScPtBi to a ferromagnetic half-metal with a 100% spin polarization at the Fermi level. The degenerated d orbitals of vanadium have caused severe electronic states near the Fermi level, which has led to a shift in the trend of the Seebeck coefficient from positive to negative values, and the p-type behavior can be seen for both ScPtBi and VPtBi modes. The highest Seebeck of these compounds are 198 and 169 µVK−1, respectively. The obtained maximum figure of merit (ZT) values also show that the ScPtBi is suitable for thermoelectric applications at room temperatures, while VPtBi will perform well at high temperatures. Our calculations have shown that the ScPtBi has high hardness with 202.09 GPa bulk modulus.

In this study, we have investigated the structural, electronic, and magnetic properties of the Rb2NaVF6 compound. We have performed our calculations by the use of first-principle methods based on spin-polarized density functional theory, where the electronic exchange-correlation potential is treated by the generalized gradient approximation GGA- PBEsol coupled with the improved TB-mBJ approach. The calculated structural parameters of Rb2NaVF6 are in good agreement with the available experimental data. Rb2NaVF6 exhibits a half-metallic ferromagnetic feature with a spin polarization of 100 % at the Fermi level and a direct large half-metallic gap of 3.582 eV. The total magnetic moments are 2 μB. This material is half-metallic ferromagnets, and it can be potential candidates for spintronics applications at a higher temperature.

Taking into account the electron spin mobility, the paper considers the numerical solution to the equation for nonequilibrium spin polarization at the boundary of a magnetic contact with a current formed by two ferromagnets. The frequencies of spin injection radiation are calculated. It is shown that at a certain current density exceeding the threshold value, these frequencies lie in the terahertz frequency range. It was found that for the same terahertz frequency range, even for small values of the difference in the mobility of electrons with spin up and down, the current density can be two orders of magnitude lower than the current density with the same mobility.

A two-dimensional topological insulator (2DTI) has an insulating bulk and helical edges robust to nonmagnetic backscattering. While ballistic transport has been demonstrated in micron-scale 2DTIs, larger samples show significant backscattering and a nearly temperature-independent resistance of unclear origin. Spin polarization has been measured, however the degree of helicity is difficult to quantify. Here, we study 2DTI few-layer Na3Bi on insulating Al2O3. A nonlocal conductance measurement demonstrates edge conductance in the topological regime with an edge mean free path ∼100 nm. A perpendicular magnetic field suppresses spin-flip scattering in the helical edges, resulting in a giant negative magnetoresistance (GNMR) up to 80% at 0.9 T. Comparison to theory indicates >96% of scattering is helical spin scattering significantly exceeding the maximum (67%) expected for a nonhelical metal. GNMR, coupled with nonlocal measurements, thus provides an unambiguous experimental signature of helical edges that we expect to be generically useful in understanding 2DTIs.

The half-metallic, mechanical, and thermoelectric properties of the Co2TiSn in bulk and [001] films were investigated based on density functional theory (DFT) and full-potential linear augmented plane waves plus local orbitals method (FP-LAPW+LO). The exchange-correlation functional was approximated by generalized gradient approximation (GGA). The Co2TiSn bulk has mechanical stability in three static, dynamic, and elastic forms. All phonon branches have positive frequencies, and elastic results have shown the hardness with brittle behavior for this case. The Co2TiSn has half-metallic nature with full spin polarization at the Fermi energy and 2.0 μB magnetic moment. It also has a good figure of merit (ZT) about one that makes it suitable for thermoelectric applications. All four Co–Co, Co–Sn, Ti–Sn, and Ti–Co terminations of the [001] films have the ground state point. However, the Ti–Sn termination has half-metallic property so that in the up-spin it is metal and in the down-spin it is a semiconductor with an indirect energy gap of 0.3 eV. The thermoelectric behavior of the Ti–Sn termination has shown big Seebeck coefficient S with a positive sign and in lower temperatures, and the ZT amount around one in this temperature range. Moreover, the power factor (PF) of this case has a significant peak in the room temperature.

In this study, spin polarization efficiency and spin-dependent transmission of electrons passing through a multiple quantum well structure with constant total effective length (60 nm) made of GaAs/Al0.3Ga0.7As, which was grown along [001] direction, were investigated. The calculations were done with the quantum transmitting boundary method. We presented the number of wells in a constant total length as a tuning tool for spin filtering purposes. In some energy intervals, 100% spin polarization and spin-dependent transmission were observed.

Among the vast pyrochlore group, oxide bismuth pyrochlores are quite interesting owing to the presence of stereochemically active lone pair electrons of bismuth and prominent Jahn-Teller interactions of the pyrochlore constituent cations leading to interesting structural modifications as well as emerging physical phenomenon of fundamental and technological significance. Particularly the bismuth pyrochlores nominally denoted by (Bi,M)MNO7-δ (M = transition metal, N= Nb, Ta, Sb) crystallizing with cubic symmetry at ambient conditions are intriguing due to the presence of ionic displacements and mixed cation occupancy especially at Bi site leading to non-stoichiometry and tunability of the physical properties with composition. Magnetic properties of the pyrochlore lattice has also garnered much attention as spin polarization on the frustrated square lattice indicated distinctive magnetic ground states such as spin glass, spin ice and spin liquid. In these cubic pyrochlores large cationic displacements coupled with uncontrolled random hopping, mixed cation crystallographic site occupancy and compositional variability gave rise to tunable dielectric relaxation. The cubic pyrochlore have been well known for showing low temperature as well as high temperature dielectric relaxation. Although long-range magnetic order was not supported on a bismuth pyrochlore lattice, recent findings reflected polar nature at room temperature in some of these disordered cubic pyrochlores comprising of highly polarizable cations. Herein we summarize the state of art in the exploration of cubic pyrochlores of Bi, and Nb/Ta/Sb in combination with various transition metals occupying multiple crystallographic sites. Their interesting structural, dielectric, magnetic properties and device applications are highlighted. Current challenges in the understanding of these materials are discussed and conclusions are put forth.

The ultrafast demagnetization effect allows for the generation of femtosecond spin current pulses, which is expected to extend the fields of spin transport and spintronics to the femtosecond time domain. Thus far, directly observing the spin polarization induced by spin injection on the femtosecond time scale has not been possible. Herein, we present time- and spin-resolved photoemission results of spin injection from a laser-excited ferromagnet into a thin gold layer. The injected spin polarization is aligned along the magnetization direction of the underlying ferromagnet. Its decay time depends on the thickness of the gold layer, indicating that transport as well as storage of spins are relevant. This capacitive aspect of spin transport may limit the speed of future spintronic devices., Scientific Reports, 10 (1), ISSN:2045-2322