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In this work, we investigate the effect of anti-site disorder on the half-metallic properties of a Mn2FeAl Heusler alloy thin film. The film was grown on TiN-buffered MgO 001 substrates via magnetron sputtering. A detailed structural characterization using x-ray diffraction (XRD) and anomalous XRD showed that the film crystallizes in the partially disordered L21 B structure with 33% disorder between the Mn(B) and Al(D) sites. We measure a positive anisotropic magnetoresistance in the film, which is an indication of non-half metallic behaviour. Our x-ray magnetic circular dichroism sum rules analysis shows that Mn carries the magnetic moment in the film, with a positive Fe moment. Experimentally determined moments correspond most closely with those found by density functional calculated for the L21 B structure with Mn(B) and Al(D) site disorder, matching the experimental structural analysis. We thus attribute the deviation from half-metallic behaviour to the formation of the L21 B structure. To realize a half-metallic Mn2FeAl film it is important that the inverse Heusler XA structure is stabilized with minimal anti-site atomic disorder.

The observation of in-plane ferromagnetism in layered magnetic materials in conjunction with the topological nodal-ring dispersion in a spin gapless semimetal with 100 % spin polarization has a fertile ground for novel physics, rich scientific significance and for the next-generation advanced spintronic and topological devices. Topological nodal ring spin gapless semimetals with large band gap in the other spin channel prevents the spin leakage and are excellent spintronic materials. On the basis of density functional theory (DFT), we have studied the layered magnetic perovskite, CsMnF4 which is predicted to be a ferromagnetic insulator though the fellow compounds like AMnF4 (A = Na, K, Rb) are anti-ferromagnetic in nature. DFT + U calculations reveal that this layered system undergoes a transition from an insulating to half-semimetallic nature with decreasing on-site Hubbard Coulomb interaction, U. For U = 2.5 eV, we observe the topological nature in the system with the emergence of four Mexican hat like dispersions associated with band-flipping. Also, we calculated the magneto-crystalline anisotropic energy with inclusion of spin-orbit coupling (SOC) and found that the system consists of in-plane ferromagnetism. Transport properties infer huge anisotropy of one order of magnitude between 'a' and 'c' axes. Interestingly, the estimated Fermi velocities are 2.66 × 105 and 2.24 × 105 m s-1 for Z(=0) and Z(=0.5) plane respectively and are comparable to that of graphene, which might fetch applications in high speed spin electronic devices. The topological phase observed is robust to SOC and the band-crossings associated with nodal rings could be preserved by additional symmetry as the time-reversal symmetry breaks in magnetic systems. The nearly charge compensation observed from Fermi surfaces might fetch memory device applications.

The dwell time and spin polarization (SP) of electrons tunneling through a parallel double δ-magnetic-barrier nanostructure in the presence of a bias voltage is studied theoretically in this work. This nanostructure can be constructed by patterning two asymmetric ferromagnetic stripes on the top and bottom of InAs/Al x In1 – x As heterostructure, respectively. An evident SP effect remains after a bias voltage is applied to the nanostructure. Moreover, both magnitude and sign of spin-polarized dwell time can be manipulated by properly changing the bias voltage, which may result in an electrically-tunable temporal spin splitter for spintronics device applications.

Based on first-principles calculations, the unconventional Rashba- and Zeeman-type spin splitting can simultaneously coexist in the Pb-adsorbed monolayer WSe2 system. The first two adsorption configurations t 1 and t 2 show remarkable features under the spin–orbit coupling, in which two split energy branches show same spin states at the left or right side of Γ, and the spin polarization is reversed for both Rashba band branches. For the second adsorption configuration, an energy gap was observed near the unconventional spin polarization caused by the repelled Rashba bands for avoid crossing, and this gap can produce non-dissipative spin current by applying the voltage. The results for t 2 configuration with spin reversal show that the repel band gap and Rashba parameter can be effectively regulated within the biaxial strain range of −8% to 6%. By changing the adsorption distance d between Pb and the neighboring Se atom layer, the reduced d caused the transfer from Rashba-type to Zeeman-type spin splitting. This predicted adsorption system would be promising for spintronic applications.

Spin-orbit (SO) coupling combined with space inversion symmetry breaking is at the origin of the lifting of the spin degeneracy in the band structure of many materials. The momentum-dependent energy splitting and the degree of spin polarization are indicative of the strength and symmetry of the SO interaction, and enter in the figure of merit of essentially all conceptual designs aiming to control the electron spin degree of freedom in solids. Here we briefly review the role played by spin-and-angle-resolved photoemission (spin ARPES or SARPES) in revealing the spin polarization specifically in the topological states of 3-dimensional (3D) topo- logical insulators (TIs), and we discuss how the progress in the technique can assist the rise of several active fields like spintronics, spin-orbitronics or the generation of spin-polarized beams.

Recently, two-dimensional (2D) BCN, an in-plane heterostructure formed by graphene and hexagonal boron nitride, has been successfully synthesized experimentally and exhibits diverse electronic properties. Unfortunately, it has been slow on the application of 2D BCN for spintronics due to the lack of the magnetic ordering. Here, using density functional theory calculations, we explored the effect of vacancy defect and biaxial strain on the electronic and magnetic properties of BCN monolayer. It is demonstrated that BCN monolayer can be converted from nonmagnetic semiconductor to magnetic half-metal/metal by introducing C or B vacancies. The half-metal/metal behavior can be remained under the different vacancy concentrations in defective BCN monolayer. In addition, BCN monolayer with C and B vacancies can be converted between half-metal and metal by applying biaxial strain. Moreover, the magnetic properties of defective BCN monolayer can also be efficiently modulated under the biaxial strain by regulating the spin polarization of the C/N/B 2porbitals. Our findings not only provide an effective way to achieve half-metal/metal transition, but also can induce and manipulate the magnetism of BCN monolayer, which may be utilized for the development of 2D BCN spintronic nanodevices.

The electronic structures and magnetic properties of diverse transition metal (TM = Fe, Co, and Ni) and nitrogen (N) co-doped monolayer MoS2 are investigated by using density functional theory. The results show that the intrinsic MoS2 does not have magnetism initially, but doped with TM (TM = Fe, Co, and Ni) the MoS2 possesses an obvious magnetism distinctly. The magnetic moment mainly comes from unpaired Mo:4d orbitals and the d orbitals of the dopants, as well as the S:3p states. However, the doping system exhibits certain half-metallic properties, so we select N atoms in the V family as a dopant to adjust its half-metal characteristics. The results show that the (Fe, N) co-doped MoS2 can be a satisfactory material for applications in spintronic devices. On this basis, the most stable geometry of the (2Fe–N) co-doped MoS2 system is determined by considering the different configurations of the positions of the two Fe atoms. It is found that the ferromagnetic mechanism of the (2Fe–N) co-doped MoS2 system is caused by the bond spin polarization mechanism of the Fe–Mo–Fe coupling chain. Our results verify that the (Fe, N) co-doped single-layer MoS2 has the conditions required to become a dilute magnetic semiconductor.

The fascinating Dirac cone in honeycomb graphene, which underlies many unique electronic properties, has inspired the vast endeavors on pursuing new two-dimensional (2D) Dirac materials. Based on the density functional theory method, a 2D material Zn3Si2 of honeycomb transition-metal silicide with intrinsic Dirac cones has been predicted. The Zn3Si2 monolayer is dynamically and thermodynamically stable under ambient conditions. Importantly, the Zn3Si2 monolayer is a room-temperature 2D Dirac material with a spin–orbit coupling energy gap of 1.2 meV, which has an intrinsic Dirac cone arising from the special hexagonal lattice structure. Hole doping leads to the spin polarization of the electron, which results in a Dirac half-metal feature with single-spin Dirac fermion. This novel stable 2D transition-metal-silicon-framework material holds promises for electronic device applications in spintronics.

The needs of high speed performance electronic devices for various applications require novel materials and new physical phenomena. For these purposes we propose to study new physical effects based on electron scattering on magnetic skyrmions and vortices distributed in a 2D ferromagnetic material. We show that the topological spin Hall effect can be efficiently employed for the filtering, switching, and separation of spin currents. For some values of the parameters (conduction electron concentrations, and skyrmion/vortex sizes) it is possible to separate Hall currents for different electron spin projections as it is like for different carrier charges (electrons and holes) in the normal Hall effect. The calculations are performed using the Boltzmann kinetic equation for the nonequilibrium distribution function and the Lippmann-Schwinger equation for the transition matrix in the whole range of the adiabaticity parameter. The spin filtering due to the skyrmion/vortex scattering can be several orders of magnitude more efficient in the narrow range of the electron concentrations than that of the ordinary ferromagnetic spin polarization in spintronics.

The realization of spin gapless semiconductor (SGS) and half-metal (HM) behavior in two-dimensional (2D) transition metal (TM) dichalcogenides is highly desirable for their applications in spintronic devices. Here, using density functional theory calculations, we demonstrate that Fe, Co, Ni substitutional impurities can not only induce magnetism in MoSe2 monolayer, but also convert the semiconducting MoSe2 to SGS/HM system. We also study the effects of mechanical strain on the electronic and magnetic properties of the doped monolayer. We show that for all TM impurities we considered, the system exhibits the robust SGS/HM behavior regardless of biaxial strain values. Moreover, it is found that the magnetic properties of TM-MoSe2 can effectively be tuned under biaxial strain by controlling the spin polarization of the 3d orbitals of Fe, Co, Ni atoms. Our findings offer a new route to designing the SGS/HM properties and modulating magnetic characteristics of the TM-MoSe2 system and may also facilitate the implementation of SGS/HM behavior and realization of spintronic devices based on other 2D materials.

Using the Su-Schrieffer-Heeger Hamiltonian and exploiting the Green's function method in the framework of the Landauer-Büttiker formalism, the topological and spin dependent electron transport properties of a trans polyacetylene molecule are studied. It is found that molecules with the intracell single carbon-carbon bonding and the even number of monomers in their chains have two edge states and possess topological properties though their Hamiltonians do not respect the chiral symmetry. A perpendicular exchange magnetic field and two perpendicular and transverse electric fields are used to induce and manipulate the quantum spin dependent electron transport properties. The exchange field induces the spin polarization in different electron energy regions which are expanded by stronger exchange fields. Therefore this proposed device works as a perfect spin filter. The spin polarization can be manipulated by applying the perpendicular electric field and remains robust against the transverse electric field variations.

In order to search for stable ferromagnets with high spin polarization in Heusler alloys for spintronic applications, we develop an efficient machine learning workflow based on a deep neural network, whose training data were collected from the open quantum materials database and high throughput calculation by first-principle calculations. The lattice constants, formation energy and spin polarization of 10 577 candidate materials were predicted, and 192 materials with high spin polarization were selected according to a spin polarization greater than 0.87 and formation energy less than 80 meV/atom. 57 of these alloys have been reported as Half-metal (100% spin polarization) according to previous researches, and 18 have been reported as semiconductors. Especially, 6 Heusler alloys were identified as promising half-metallic ferromagnets, and some of them have high Curie temperature above room temperature. Our study suggests this approach is an efficient method for the discovery of superior spintronic materials, which should be also suitable for exploring other functional materials.

Spintronics addresses the spin degree of freedom of electrons as an analog of the traditional information technology approach toward the charge degree of freedom. Two-dimensional (2D) materials have provided a new platform for spintronics since the successful isolation of graphene in 2004. In this review, we discuss the recent progress of chromium tri-iodide (CrI3), phosphorene, silicene, germanene, stanene, animonene, and borophene in spintronics. Among these 2D materials, CrI3 has intrinsic magnetism, while the others are single-element 2D materials (Xenes) without intrinsic magnetism. A review is presented of works based on different research methods, including experimental, theoretical, and simulation studies. Various morphologies of 2D materials are included, such as monolayers, bilayers, nanoribbons, heterojunctions, and nanoflakes of different shapes. The effect of atomic doping, vacancies, line defects, strain, and external fields is also summarized. Among the properties and applications of these materials, the spin polarization, spin/valley-dependent resistance, various Hall effects, RKKY interaction, Rashba effect, and topological phase are the most widely studied topics. Over the past two years, various novel spintronics devices have been designed based on 2D materials, and numerous fundamental functions in spintronics have been realized. Thus, we also summarize the emerging novel devices in this field. Finally, we present a summary of the remaining challenges and possible future directions.

Recent experiments revealed the unusual strong spin effects with high spin selective transmission of electrons in double-stranded DNA. We propose a new mechanism that the strong spin effects could be understood in terms of the combination of the chiral structure, spin-orbit coupling, and especially spin-dependent Anderson localization. The presence of chiral structure and spin-orbit coupling of DNA induce weak Fermi energy splitting between two spin polarization states. The intrinsic Anderson localization in generic DNA molecules may result in remarkable enhancement of the spin selective transport. In particular, these two spin states with energy splitting have different localization lengths. Spin up/down channel may have shorter/longer localization length so that relatively less/more spin up/down electrons may tunnel through the system. In addition, the strong length dependence of spin selectivity observed in experiments can be naturally understood. Anderson localization enhanced spin selectivity effect may provide a deeper understanding of spin-selective processes in molecular spintronics and biological systems.

Next generation of spintronic devices aims to utilize the spin-polarized current injection and transport to control the magnetization dynamics in the spin logic and memory technology. However, the detailed evolution process of the frequently observed bias current-induced sign change phenomenon of the spin polarization has not been examined in details and the underlying microscopic mechanism is not well understood. Here, we report the observation of a systematic evolution of the sign change process of Hanle spin precession signal in the graphene nonlocal spintronic devices at room temperature. By tuning the interface tunnel resistances of the ferromagnetic contacts to graphene, different transformation processes of Hanle spin precession signal are probed in a controlled manner by tuning the injection bias current/voltage. Detailed analysis and first-principles calculations indicate a possible magnetic proximity and the energy dependent electronic structure of the ferromagnet-graphene interface can be responsible for the sign change process of the spin signal and open a new perspective to realize a spin-switch at very low bias-current or voltage.

We studied the spin transport properties of an oxygen-terminated armchair graphene nanoribbon (O-AGNR) with a single edge vacancy via an ab-initio calculation based on density functional theory combined with the nonequilibrium Green's function technique. We found that spin-filtering occurs regardless of the ribbon width by introducing an edge vacancy on one edge side of the O-AGNR because the four energy bands mainly consisted of the oxygen p orbital, such that the up-spin states were localized on one edge side and the down-spin states were on the other edge side. Moreover, we showed that the absolute value of spin-filtering efficiency reached ~1.00 at certain values of the chemical potential; additionally, the direction of spin polarization can be switched by controlling the chemical potential. These results suggest that O-AGNRs have potential applications in spintronics devices.

Electric gating provides a versatile tool to create new spintronic materials and functionalities. Here, we have shown significant tuning effects of the gate voltage via ionic liquid on spin pumping and spin Hall magnetoresistance in Pt/yttrium iron garnet heterostructure. It is found that the interfacial spin mixing conductance is greatly enhanced upon application of the gate voltage. In addition, and interestingly, the spin relaxation time also increases with the gate voltage. Moreover, suppressed spin Hall magnetoresistance and enhanced spin polarization of Pt atoms both suggest that the spin Hall angle is reduced by the gate voltage. All these results can be consistently explained by the enhanced charge carrier density and the subsequent elevated Fermi level induce by the gate voltage. By tackling the key parameters in controlling the generation and propagation of pure spin current via voltage gating, the present work provides novel strategies to improve the performance of the spin current devices.

Electrically controllable magnetic properties in 2D materials are promising for the development of the next-generation of magnetic and spintronic applications. In this paper, a theoretical design of magnetic property modulation in an Fe-doped GaSe monolayer is provided based on systematical density functional theory calculations. A ferromagnetic coupling between Fe and the vicinal Ga atom in the Fe-doped GaSe monolayer is found to be regulated to an antiferromagnetic coupling at a critical electric field of 0.2 V ??1, accompanied with the change of the magnetic moment and the spin polarization. By calculating the magnetization energy, total energy, charge redistribution, and orbital-decomposed densities of states, the significant effect of the electric field on the magnetic configuration and magnetic anisotropy in the Fe-doped GaSe monolayer is analyzed, and the related physics mechanism is revealed. The electric-field tunable magnetic properties offer a promising application in magnetic and spintronic devices.

A comprehensive first-principles study of the correlation between zero-energy states and the tunability of the spin-selective semiconducting properties of zigzag-edged bowtie-shaped graphene nanoflakes under an electric field is presented for the first time. We demonstrate that the spin degenerate semiconducting ground state can be lifted by the electric field. In particular, we find that the number of zero-energy states ('the nullity') defined by the structural configuration determines the complexity and efficiency of the tunability of spin polarization. The fine-tuning of spin-dependent properties by the electric field originates from the manipulation of spin-polarized molecular orbital energies. We expect this study to aid the design of more effective and controllable low-dimensional molecular spintronics.

Applications of semiconductors in spintronics are being developed and revolutionized to fabricate nanostructures in which the spin current is injected, detected and manipulated. The manifestation of the spin Hall effect (SHE) in semiconductors with a simple geometry is still a challenge to implement in spintronics. In this work, we demonstrate the distinct electrical detection of the inverse spin Hall effect (ISHE) in WS2 multilayer crystals at temperatures ranging from 4.2 K to 300 K. The novel idea of this study is the electrical detection of the ISHE in WS2 using an in-plane spin-polarized current, which is realized using non-ferromagnetic electrodes on the top and bottom surfaces of the WS2 channel. The flow alteration of spin-polarized current results in a polarity change in the inverse spin Hall signal. By analyzing the magnitude of the ISHE, we estimated a spin diffusion length of ~250 nm, spin Hall angle of ~0.028, spin polarization of ~0.20 and spin lifetime of ~560 ps in WS2-layered crystals at room temperature. The ISHE in layered, 2D materials, including WS2 crystals, provides a new methodology to develop low-power and fast memory devices to write, read and store information.

We investigate a novel way to manipulate the spin polarized transmission in a two terminal zigzag graphene nanoribbon in presence of Rashba spin-orbit (SO) interaction with circular shaped cavity engraved into it. A usual technique to control the spin polarized transport behaviour of a nanoribbon can be achieved by tuning the strength of the SO coupling, while we show that an efficient engineering of the spin polarized transport properties can also be done via cavities of different radii engraved in the nanoribbon. Simplicity of the technique in creating such cavities in the experiments renders an additional handle to explore transport properties as a function of the location of the cavity in the nanoribbon. Further, a systematic assessment of the interplay of the Rashba interaction and the dimensions of the nanoribbon is presented. These results should provide useful input to the spintronic behaviour of such devices. In addition to the spin polarization, we have also included an interesting discussion on the charge transmission properties of the nanoribbon, where, in absence of any SO interaction a metal-insulator transition induced by the presence of a cavity is observed., 7 pages, 9 figures (Accepted in Europhysics Letters)

By means of the Keldysh Green's function method, we investigate the spin-polarized electron transport in a three-terminal device, which is composed of three normal metal leads and two serially-coupled quantum dots (QDs). The Rashba spin-orbit interaction (RSOI) is also considered in one of the QDs. We show that the spin-polarized charge current with arbitrary spin polarization can be obtained because of the quantum spin interference effect arising from the Rashba spin precession phase, and it can be modulated by the system parameters such as the applied external voltages, the RSOI strength, the QD levels, as well as the dot-lead coupling strengths. Moreover, a fully spin-polarized current or a pure spin current without any accompanying charge current can also be controlled to flow in the system. Our findings indicate that the proposed model can serve as an all-electrical spin device in spintronics field.

Based on first-principles calculations, the evolution of hybrid interface states (HISs) from a single spinterface to a magnetic molecular junction and their contribution to the spin-dependent electron transport are investigated. It is demonstrated that the spin polarization of HISs may be conserved or eliminated by relying on the spin configuration of the electrodes. By comparing the results of 1,4-benzene-dithiolate (1,4-BDT) and 1,3-benzene-dithiolate (1,3-BDT) magnetic junctions, the transport calculations explore two entirely different transmission abilities of HISs. An efficient transmission close to 1 is achieved for the 1,4-BDT junction while a strongly suppressed one (~0.1) is achieved for the 1,3-BDT junction. An apparent enhancement of magnetoresistance by HISs is realized in the 1,4-BDT junction. The intrinsic mechanism is revealed by analyzing the transmission pathway and interfacial structures. This work indicates the promising prospect of HISs in improving the performance of molecular spintronic devices in the case of suitable interfacial designs.

Alloying effects by Mn and Ni substitution on FeS2 have been studied using density-functional calculations. Standard generalized gradient approximation (GGA) and local hybrid functional have been utilized to account for exchange-correlations. The alloys Fe1-x T x S2 with T = Mn,Ni have been investigated for concentrations [Formula: see text] together with the ground states of the pure compounds. The electronic structure is discussed with the main goal to identify candidates for ferromagnetic half-metals, which are of interest for spintronics applications. Depending on the used calculation framework, interesting candidates have been found at different concentrations. However, at mean concentration of the Mn-doping and low concentration for Ni-doping, both GGA and hybrid functional agree to predict half-metallic character. For the Mn alloys we also note the proximity to a low-spin to high spin transition.

To realize a graphene based spintronic device, the prime challenge is to control the electronic structure of edges. In this work we find the origin of the spin filtering property in edge boron doped zigzag graphene nanoribbons (ZGNRs) and provide a guide to preparing a graphene based next-generation spin filter based device. Here, we unveil the role of orbitals (p-electron) to tune the electronic, magnetic and transport properties of edge B doped ZGNRs. When all the edge carbon atoms at one of the edges of ZGNRs are replaced by B (100% edge B doping), the system undergoes a semiconductor to metal transition. The role of passivation of the edge with single/double atomic hydrogen on the electronic properties and its relation with the p-electron is correlated in-depth. 50% edge B doped ZGNRs (50% of the edge C atoms at one of the edges are replaced by B) also show half-metallicity when the doped edge is left unpassivated. The half-metallic systems show 100% spin filtering efficiency for a wide range of bias voltages. Zero-bias transmission function of the other configurations shows asymmetric behavior for the up and down spin channels, thereby indicating their possible application potential in nano-spintronics.

Thermoelectric transport properties of Ti doped or adsorbed monolayer blue phosphorene are investigated by density functional theory combined with the nonequilibrium Green's function formalism. The thermal giant magnetoresistance and a nearly 100% spin polarization which solely relies on the temperature gradient of electrodes without bias or gate voltage are observed. Moreover, the spin Seebeck effect is also found. Furthermore, taking into account the electronic and phonon dispersion, the thermoelectric merit for Ti doping in the monolayer blue phosphorene at room temperature is also studied, the maximum value of thermoelectric merit can reach 1.01 near the Fermi level. The results indicate that Ti doped or adsorbed monolayer blue phosphorene has potential application in both spintronics and spin caloritronics.

Mn2CrGa-based Heusler compounds combining small magnetization with high spin polarization, fabricated by Fe and Pt substitution for Cr, are investigated experimentally and discussed in terms of sublattice site occupancies. X-ray diffraction and electron diffraction indicate that the parent alloy and Mn2Cr0.6Fe0.4Ga are normal cubic Heusler alloys with substantial chemical disorder, whereas Mn2Cr0.6Pt0.4Ga crystallizes in the tetragonal D022 structure. Magnetization measurements indicate that the spin structure of the parent alloy is essentially ferrimagnetic, but alloying with Fe or Pt reduces the net magnetization per formula unit from 0.40 µ B in the parent alloy to nearly zero in the Fe case. The Curie temperature, the magnetoresistance, and the Andreev-reflection transport-spin polarization are less affected by the substitutions, the last changing from 65% in Mn2CrGa to 60% and 61% in the Fe- and Pt-substituted alloys, respectively. The properties of these alloys are favorable for spintronics applications.

Regulation of ferromagnetism and electronic structure in PtSe2 nanostructures has attracted much attention because of its potential in spintronics. The magnetic and optical properties of PtSe2 nanoribbons with different edge reconstruction and external deformations are calculated by density function theory. In 1 T phase PtSe2 nanoribbons, the ferromagnetism induced by spin polarization of exposed Pt or Se atoms is decreased with the reducing nanoribbon width. For smaller nanoribbon, the magnetism can be regulated by external strain more easily. However, the magnetism cannot occur in 1 H phase PtSe2 nanoribbon. The absorption spectra are suggested to identify the nanoribbon structural changes in detail. Our results suggest the use of edge reconstruction and strain engineering in spintronics applications.

First-principles calculations are conducted to study the electronic and magnetic states of Mn-doped monolayer MoS2 under lattice strain. Mn-doped MoS2 exhibits half-metallic and ferromagnetic (FM) characteristics in which the majority spin channel exhibits metallic features but there is a bandgap in the minority spin channel. The FM state and the total magnetic moment of 1 µ B are always maintained for the larger supercells of monolayer MoS2 with only one doped Mn, no matter under tensile or compressive strain. Furthermore, the FM state will be enhanced by the tensile strain if two Mo atoms are substituted by Mn atoms in the monolayer MoS2. The magnetic moment increases up to 0.50 µ B per unit cell at a tensile strain of 7%. However, the Mn-doped MoS2 changes to metallic and antiferromagnetic under compressive strain. The spin polarization of Mn 3d orbitals disappears gradually with increasing compressive strain, and the superexchange interaction between Mn atoms increases gradually. The results suggest that the electronic and magnetic properties of Mn-doped monolayer MoS2 can be effectively modulated by strain engineering providing insight into application to electronic and spintronic devices.

Perpendicular magnetic anisotropy is significantly important for realizing a long-term retention of information for spintronics devices. Inspired by 2D graphene with its high charge carrier mobility and long spin diffusion length, we report a first-principles design framework on perpendicular magnetic anisotropy engineering of a Fe atom adsorbed graphene by employing a O-terminated MgO (1 1 1) substrate. Determined by the adsorption sites of the Fe atom, a tunable magnetic anisotropy is realized in Fe/graphene/MgO (1 1 1) structure, with the magnetic anisotropy energy of −0.48 meV and 0.23 meV, respectively, corresponding to the in-plane and out of plane easy magnetizations. Total density of states suggest a half-metallicity with a 100% spin polarization in the system. Decomposed densities of Fe-3d states reveal the orbital contributions to the magnetic anisotropy for different Fe adsorption sites. Bonding interaction and charge redistribution regulated by MgO substrate are found responsible for the novel perpendicular magnetic anisotropy engineering in the system. The effective manipulation of perpendicular magnetic anisotropy in present work offers some references for the design and construction of 2D spintronics devices.

Ferromagnetic Heusler compounds have vast and imminent applications for novel devices, smart materials thanks to density functional theory (DFT) based simulations, which have scored out a new approach to study these materials. We forecast the structural stability of Co2TaZ alloys on the basis of total energy calculations and mechanical stability criteria. The elastic constants, robust spin-polarized ferromagnetism and electron densities in these half-metallic alloys are also discussed. The observed structural aspects calculated to predict the stability and equilibrium lattice parameters agree well with the experimental results. The elastic parameters like elastic constants, bulk, Young's and shear moduli, poison's and Pugh ratios, melting temperatures, etc have been put together to establish their mechanical properties. The elaborated electronic band structures along with indirect band gaps and spin polarization favour the application of these materials in spintronics and memory device technology.

We study the charge and valley-spin ballistic transport through monolayer (ML) WSe2 potential barrier, of width and height , in the presence of an off-resonant light and ferromagnetic (FM) exchange field. We show that an electric switch is available in WSe2 by increasing beyond the critical value . Due to the band gaps of valley and responding differently to off-resonant light together with the huge spin–orbit coupling (SOC) in WSe2, the perfect valley and spin polarizations are obtained. Interestingly, under the effect of electrostatic potential , the valley polarization can be realized even for a tiny light intensity. Additionally, the FM exchange field can assist significantly the spin polarization in a wider region of light intensity and barrier height plane due to the large shift of spin-up and down bands. More important in our results, the highest valley and spin conductance is near 100% even under the polarized situation. These results demonstrate that WSe2 is a distinguished 2D material for novel spintronics and valleytronics in future.

We propose and theoretically analyse a double magnetic tunnel device that takes advantages of the spin filter effect. Two magnetic tunnel barriers are formed by different spin filters which have different barrier heights. The magnetoresistance of the device is low (high) when the magnetic moments of the two spin filters are parallel (antiparallel). We present a theoretical calculation of the magnetoresistance based on electric tunnel effect. In addition, the effect of the difference barrier heights and exchange splitting energies between the two spin filters are also analysed in detail. The numerical results show that the spin filter in this configuration gives a magnetoresistance larger than that with standard magnetic tunnel junctions.

In order to search for promising candidates for spintronic applications, this paper systematically studies three ternary compounds based on Mn5Ge3 by using a full-potential linearized augmented plane wave method within the density functional theory. Through structure optimization and electronic structure calculations, it finds that Mn4FeGe3 and Mn4CoGe3 have much higher spin-polarization than original intermetallic compound Mn5Ge3, although the spin polarization of Mn4NiGe3 is lower than that of Mn5Ge3. The calculated result is in agreement with experiment in the case of Mn4FeGe3. Both of them can be taken as promising candidates for spintronics applications because of their high spin-polarization and compatibility with semiconductors.

Using the Keldysh nonequilibrium Green function and equation-of-motion technique, this paper investigates the spin-polarized transport properties of the T-shaped double quantum dots (DQD) coupled to two ferromagnetic leads. There are both Fano effect and Kondo effect in the system, and due to their mutual interaction, the density of states, the current, and the differential conductance of the system depend sensitively on the spin-polarized strength. Thus the obtained results show that this system is provided with excellent spin filtering property, which indicates that this system may be a candidate for spin valve transistors in the spintronics.

We fabricated heterojunctions using organic semiconductor pentacene sandwiched between two different magnetic electrodes: Co-doped TiO2 (Co:TiO2) and Fe. The conductance of the junctions was measured as a function of magnetic field. We found that the characteristics of the junctions are strongly dependent on the method used to deposit the Fe top electrode on pentacene. The magnetotransport properties can be explained by the effect of the interface morphology and spin polarization of interface traps.

A theory is developed for the treatment of magneto transport properties and spin dynamics in magnetic nanowire that contains a domain wall (DW), i.e. a region of non-collinearity. The method is applicable when the wavelength of spin up and down electrons are larger than the DW width in which case the problem is solvable exactly as a spin-resolved scattering from a strongly localized spin-dependent effective potential created by DW. We present calculations for the current-induced spin density, the distribution of the spin currents, and the spin torque acting locally on the magnetic moments within DW. We also discuss an extension based on the weak gradient (adiabatic) perturbation arising after a local transformation to a uniform magnetization.

On the basis of the Rashba spin?orbit interaction, we propose and investigate a mesoscopic spin interferometer for generating spin polarized current. We find that the output current is in general spin polarized if the interferometer is a multi-terminal device with two non-equal-length arms. We study the dependence of the spin polarization and output probability on the system parameters, and find that both of them can be quite large, simultaneously. The suggested device does not contain any magnetic material or magnetic field; moreover, the spin?orbit interaction can be either uniform or non-uniform. This spin device can be realized with today's technology.

We theoretically investigate the spin current for a parabolically confined semiconductor heterojunction quantum wire with weak Rashba spin-orbit coupling by means of the perturbation method. By analytical calculation, it is found that only two components of spin current density is non-zero in the equilibrium case. Numerical examples have demonstrated that the spin current of electron transverse motion is 10(-3) times that of electron longitudinal motion. However, the former one is much more sensitive to the strength of Rashba spin-orbit coupling. These results may suggest an approach to the spin storage device and to the measurement of spin current through its induced electric field.

We have studied the effects of dimerization on the energy levels of a one-dimensional molecular chain attached between two electrodes. Analytic expressions for the change in energies in the presence of a small perturbing external potential have been obtained for the three limiting cases: (a) uniform, (b) partially dimerized and (c) completely dimerized chains. We find that the presence of dimerization enhances the mixing between low-lying energies in the system resulting in a situation conducive to showing negative differential resistance (NDR) in the current-voltage characteristics. The effect of spin-polarized molecule-electrode couplings on a dimerized chain has also been studied, where both spin-parallel and spin-antiparallel current show NDR behaviour. Strong dimerization however is found to destroy the spin-valve effects that are most essential for spintronic devices.

We present the electrical spin injection from room-temperature ferromagnetic (Ga, Mn)N in nitride-based spin-polarized light-emitting diodes. The electroluminescence spectra from the spin LED indicate the existence of the spin polarization via optical polarization of emitted light up to room temperature. This demonstrates that the spin injection from the (Ga, Mn)N layer into (In, Ga)N quantum wells was achieved persisting up to room temperature by comparing it with the magnetic field dependence of the Hall resistance, which is proportional to the out-of-plane magnetization. These results support that (Ga, Mn)N is an appropriate material for a spin injection source in room-temperature operating semiconductor spintronic devices.