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The control of electron spin, crucial to the stability of matter, offers new possibilities for manipulating the properties of molecules and materials with potential applications in spintronics and chemical reactions. Recent experiments have demonstrated that electron transmission through chiral molecules depends on the electron spin orientation, a phenomenon known as chiral-induced spin selectivity (CISS). In this study, we show that CISS can be observed in achiral systems driven by an external circularly polarized laser field in the framework of Floquet engineering. By using the Floquet theory for a time-periodically driven system to investigate spin-dependent electron transport in a two-terminal setup, we demonstrate that the spin polarization can approach unity if the light intensity is sufficiently strong, the rate of dephasing is sufficiently low, and the average chemical potential of the two leads is within an appropriate range of values, which is narrow because of the high frequency of the laser field. To obtain a broader range of energies for large spin polarization, a combination of chiral molecules and light–matter interactions is considered, and the spin polarization of electrons transported through a helical molecule driven by a laser field is evaluated. [ABSTRACT FROM AUTHOR]

Semiconductor spintronics has brought about revolutionary application prospects in future electronic devices. The tunnel junction plays a key role in achieving efficient spin injection in semiconductors. This work employed the GaN semiconductor as a room-temperature spin injection system, taking advantage of its weak spin–orbit coupling and spin scattering. By introducing a lattice-matched AlN barrier layer to improve the tunneling interface, advanced spin injection and transport were realized compared with traditional oxide barriers. The spin polarization was further improved by modulating the applied bias, and a bias-controlled tunneling enhancement mechanism was revealed. Consequently, we demonstrated a high record of spin polarization of 20.5%. This work paves a feasible route for achieving efficient spin injection and transport in GaN, which will further promote the development of room-temperature and high-performance spintronic devices. [ABSTRACT FROM AUTHOR]

The generation and manipulation of spin-polarized electrons are the basis of spintronic applications. Spin injection from a ferromagnetic surface or heterojunction to a semiconductor adjacent layer is often used to create spin-polarized carriers; however, for halide perovskites, due to the mismatch of lattice parameters with most ferromagnets at room temperature, this spin injection is challenging. In this study, we synthesize all-inorganic perovskite CsPbBr3 surrounded by Fe3O4 magnetic nanoparticles. It is found that this nanocomposite shows both magnetization and magnetic field-induced circularly polarized photoluminescence at room temperature. Specifically, with the attachment of Fe3O4 nanoparticles closely on the surface of CsPbBr3 nanocrystals, both the degree of circular polarization and g-factor enhanced by 3.5 times compared with that of pure CsPbBr3. The phenomenon should be due to the formation of exciton magnetic polaron through the coupling of the magnetic aligned nanoparticles with the excitonic state of the host semiconductor in the external magnetic field. The effective spin injection provides a method of controlling the excitonic spin polarization of all-inorganic halide perovskites for spintronic applications. [ABSTRACT FROM AUTHOR]

Spin–orbit coupling in chiral materials can induce chirality-dependent spin splitting, enabling electrical manipulation of spin polarization. Here, we use first-principles calculations to investigate the electronic states of chiral one-dimensional (1D) semiconductor InSeI, which has two enantiomorphic configurations with left- and right-handedness. We find that opposite spin states exist in the left- and right-handed 1D InSeI with significant spin splitting and spin-momentum collinear locking. Although the spin states at the conduction band minimum (CBM) and valence band maximum of 1D InSeI are both nearly degenerate, a direct-to-indirect bandgap transition occurs when a moderate tensile strain (∼4%) is applied along the 1D chain direction, leading to a sizable spin splitting (∼0.11 eV) at the CBM. These findings indicate that 1D InSeI is a promising material for chiral spintronics. [ABSTRACT FROM AUTHOR]

Anomalous carrier transport in magnetic Heusler compounds has evolved as a lively field of research owing to their unusual band structure and broken time-reversal symmetry. They have attractive properties for spintronics due to their high Curie temperature (Tc), high spin polarization, and extravagant transport properties. Here, we scrutinize CoFeSn. Based on the inferences from structural stability, lattice dynamics, and magnetic analysis, we propose a cubic polymorph of hexagonal CoFeSn and explain why we must consider cubic CoFeSn. Through density-functional-theory calculations, we predict a robust 3D half-metallic ferromagnetic compound, CoFeSn (P 4 ¯ 3 m) with a Tc ∼ 693 K, calculated via the Heisenberg magnetic exchange interactions under mean-field approximation, and a magnetic moment of 3 μB. In addition, Wannier interpolation suggests anomalous Hall conductivity (AHC) and spin Hall conductivity (SHC) in cubic CoFeSn, the largest SHC at the Fermi level being ≈ 47 (h/2πe) S/cm. Our theoretical results show that spin–orbit interaction at the Fermi level brings on finite Berry flux that gives an intrinsic AHC ∼ 122 S/cm at room temperature. We note that adjusting the Fermi level can be a sensible way to achieve high values of AHC or SHC. Our findings pave the way for the realization of the quantum anomalous and spin Hall effect in half-Heusler compounds. [ABSTRACT FROM AUTHOR]

The spin polarization factor was investigated using electrical spin injection at low temperatures in n+-Si(100)/MgO/ferromagnet lateral spin-valve devices with Co2Fe0.4Mn0.6Si (CFMS) and CoFe electrodes. CFMS films were annealed at different post-annealing temperatures (Ta). Although atomic diffusion of CFMS into the silicon channel was observed at high annealing temperatures, the CFMS device annealed at a Ta of 350 °C, clearly showing a narrow Hanle signal measured using the three-terminal Hanle effect; a consistent spin relaxation time of 7.1 ± 0.4 ns and spin diffusion length of 1.6 ± 0.2 μm were obtained at 10 K. A local three-terminal spin-valve (L-3TSV) signal from the CFMS lateral spin-valve device was obtained at about 370 μV, three times larger than that of the CoFe device. The tunnel spin polarization factor was evaluated from the L-3TSV signals by an analytical equation that considered the spin drift effect. The estimated tunnel spin polarization factor for CFMS was 45% at a Vbias of about 600 mV, while that for CoFe was 18%. This result indicates that the high spin polarization of CFMS is responsible for the large intensity of the L-3TSV signal and that CFMS is a promising FM material for electrical spin injection into silicon. [ABSTRACT FROM AUTHOR]

Antiferromagnetic (AFM) spintronics is an emerging field, with significant advances in particular in the study of the tunable spin generation, transport, manipulation, and detection based on the control and probe of AFM moments. The Néel-vector-dependent spin current generation in AFM materials makes them an efficient and controllable spin source, paving the way for future spintronic devices with ultralow power consumption and high operability. Herein, we aim to provide a comprehensive review of recent progress in charge-spin conversion mediated by AFMs. First, we present a brief summary of several typical characterization techniques of charge-spin conversion. Then, we focus on the recent efforts for improving the charge-spin conversion efficiency and performances of spin torques in the antiferromagnet/ferromagnet bilayer. In the third part, we review the controllable spin current and multidirectional spin polarization generated by AFMs and the resultant field-free magnetization switching. Finally, we discuss the prospects of the AFM spin sources, which will inspire more in-depth studies and advance practical applications. [ABSTRACT FROM AUTHOR]

Organic materials with mechanical flexibility, low cost, chemical engineering, and long spin lifetime attract considerable attention for building spintronic devices. Here, a C6H6/Co2MnSi(001) spinterface is investigated by first-principles calculations and spin-polarized scanning tunneling microscopy simulations. Several high symmetry adsorption sites are discussed, together with two possible surface terminations of Co2MnSi(001). An inversion of the spin polarization is induced near EF even in the case of an external electric field, indicating that C66 can act as a spin filter to exploit the spin injection efficiency in organic spintronic devices. Unlike previous studies on molecule/ferromagnet interfaces, this inversion is closely related to the electronic structure of the atoms in the subsurface layer of Co2MnSi according to the orbital symmetry analysis. Furthermore, the magnetic moment and magnetic anisotropic energy (MAE) in the outermost Co2MnSi layer are studied. Particularly, in the most stable configuration, the sign of MAE is inversed due to hybridization between C p and Co dz2 orbitals, which suggests that a greater modification on MAE can be achieved by the use of a highly chemically reactive organic molecule. These findings improve the study on the engineering of magnetic properties at molecule/ferromagnetic interfaces through a single π-conjugated organic molecule. [ABSTRACT FROM AUTHOR]

Two-dimensions Ruddlesden–Popper perovskites (RPPs) are promising materials for spintronic devices due to the spin–orbit coupling. However, a relative low spin related photoluminescence (PL) circular polarization is observed from RPPs at room temperature due to the spin relaxation and spin flip caused by the soft lattice of RPPs. Here, we report the enhancement of the circular polarization of PL of RPPs by reducing the carrier lifetime of RPPs via constructing van der Waals heterostructures. We observed the maximum PL polarization of RPPs reaching about 30%. Moreover, we found that the degree of the polarization decreases as the thickness of the heterostructure becomes thicker. Our work provides an effective method to enhance the spin polarization of RPPs and could promote the RPPs based spintronics. [ABSTRACT FROM AUTHOR]

Very recently, boron nitride atomic chains were successively prepared and observed in experiments [O. Cretu et al., ACS Nano 8, 11950 (2015)]. Herein, using a first-principles technique, we study the magnetism and spin-dependent electronic transport properties of three types of BN atomic chains whose magnetic moment is 1 µB for BnNn-1, 2 µB for BnNn, and 3 µB for BnNn+1 type atomic chains, respectively. The spin-dependent electronic transport results demonstrate that the short BnNn+1 chain presents an obvious spin-filtering effect with high spin polarization ratio (>90%) under low bias voltages. Yet, this spin-filtering effect does not occur for long BnNn+1 chains under high bias voltages and other types of BN atomic chains (BnNn-1 and BnNn). The proposed short BnNn+1 chain is predicted to be an effective low-bias spin filters. Moreover, the length-conductance relationships of these BN atomic chains were also studied. [ABSTRACT FROM AUTHOR]

We present theoretical and experimental results on tunneling current in single Fe/MgO/GaAs and double Fe/MgO/GaAs/MgO/Fe tunnel junctions. The charge and spin currents are calculated as a function of external voltage for different sets of parameters characterizing the semiconducting GaAs layer. Transport characteristics of a single Fe/MgO/GaAs junction reveal typical diode as well as spin diode features. The results of numerical calculations are compared with current-voltage characteristics measured experimentally for double tunnel junction structures, and a satisfactory agreement of the theoretical and experimental results has been achieved. [ABSTRACT FROM AUTHOR]

The spin–orbit torques (SOTs) induced by spin currents in the heavy metal/ferromagnet (HM/FM) bilayer are of great importance for enabling nonvolatile, low power consumption spintronics. In the standard HM/FM bilayers, only the spin current at the interface is employed for implementing SOTs. Another part of the spin current with the opposite spin polarization, which is generated at the opposite side of the HM layer, is supposably not put into action. Here, we will show the experimental feasibility of utilizing spin currents from the dual surfaces of the HM Pt layer. In particular, through synthesizing perpendicularly magnetized Fe 1 − x 1 Tb x 1 /Pt/ Fe 1 − x 2 Tb x 2 trilayers, we demonstrate that spin currents at the dual surfaces of the Pt layer can be simultaneously used to deterministically switch the perpendicular magnetization vectors of the neighboring Fe1-xTbx layers, through the current-induced SOTs. Based on the second harmonic measurement, we further quantify the enhanced efficiency of the current-induced SOTs. A three-dimensional spintronic device that can host an exponentially increased magnetization states is also demonstrated. Our results could be important for enabling more energy efficient spin-orbitronics that could be used in multistate memory and spin logic devices. [ABSTRACT FROM AUTHOR]

Isotropic spin analysis is a key step in spintronics and could be useful in quantum information, which usually requires light as an essential component. It has not yet been realized in a solid-state device. Here, we propose an isotropic all electrical spin analyzer designed from a quantum ring with spin–orbit couplings by analytically and numerically modeling how the charge transmission rate depends on the polarization of the incident spin. The spin transport features are also demonstrated to be robust against ring structure defects, disorder, and a bias between the two leads at finite temperature in the nanoscale ring. Similar to the light polarizer/analyzer, this interesting two-dimensional electron system can be designed as a spin filter, spin polarizer, and a general spin analyzer with high resolution by simply tuning the spin–orbit couplings, which paves the way for realizing the tunable and integrable spintronics devices. [ABSTRACT FROM AUTHOR]

The electro- and magneto-transport as well as magnetic properties of Co2MeSi (Me = Ti, V, Cr, Mn, Fe, Co, Ni) Heusler alloys were studied. The electroresistivity was measured from 4.2 to 300 K, the galvanomagnetic properties (magnetoresistivity and Hall effect) were measured at T = 4.2 K in magnetic fields of up to 100 kOe, and the magnetization at T = 4.2 and 300 K in fields of up to 70 kOe. The normal and anomalous Hall coefficients, saturation magnetization, residual resistivity, current carrier concentration, coefficients at linear contributions into the electroresistivity and magnetoresistivity were obtained. It was shown that on the one hand, there is quite clear correlation between the electronic and magnetic characteristics of Heusler alloys studied, and the spin polarization coefficients of current carriers, taken from well know literature data, on the other hand. The obtained results can be used for creation of new materials for spintronics. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the effect of Be acceptors on the electroluminescence and the spin polarization in GaAs/AlAs p-i-n resonant tunneling diodes. The quantum well emission comprise two main lines separated by ~20meV attributed to excitonic and Be-related transitions, which intensities show remarkably abrupt variations at critical voltages, particularly at the electron resonant peak where it shows a high-frequency bistability. The circular-polarization degree of the quantum-well electroluminescence also shows strong and abrupt variations at the critical bias voltages and it attains relatively large values (of ~–75% at 15 T). These effects may be explored to design novel devices for spintronic applications such as a high-frequency spin-oscillators. [ABSTRACT FROM AUTHOR]

Spin transport was studied in a two-dimensional electron gas hosted in a wide GaAs quantum well occupying two subbands. Using space and time Kerr rotation microscopy to image drifting spin packets under an in-plane accelerating electric field, optical injection and detection of spin polarization were achieved in a pump–probe configuration. The experimental data exhibited high spin mobility and long spin lifetimes allowing us to obtain the spin–orbit fields as a function of the spin velocities. Surprisingly, above moderate electric fields of 0.4 V/cm with velocities higher than 2 µm/ns, we observed a dependence of both bulk and structure-related spin–orbit interactions on the velocity magnitude. A remarkable feature is the increase in the cubic Dresselhaus term to approximately half of the linear coupling when the velocity is raised to 10 µm/ns. In contrast, the Rashba coupling for both subbands decreases to about half of its value in the same range. These results yield new information on the application of drift models in spin–orbit fields and about limitations for the operation of spin transistors. [ABSTRACT FROM AUTHOR]

The current focus of valleytronics research lies in how to produce valley polarization. Although many schemes have been broadly studied, spontaneous valley polarization is rarely explored. Here, we report the discovery of a two-dimensional material with the long-pursued spontaneous spin and valley polarizations. Using first-principles calculations, we reveal that single-layer LaBr2 is dynamically and thermally stable, which could be exfoliated from its bulk material. Single-layer LaBr2 is found to be a compelling two-dimensional ferromagnetic semiconductor. More interestingly, we show that single-layer LaBr2 harbors the extremely rare intrinsic valley polarization, owing to the coexistence of inversion symmetry and time-reversal symmetry breakings. Its spontaneous valley polarization reaches 33 meV, sizable enough for operating room-temperature valleytronic physics. Our work thus provides a promising material for experimental studies and practical applications of two-dimensional spintronics and valleytronics. [ABSTRACT FROM AUTHOR]

Spin-gapless semiconductors (SGSs), the new generation of spintronic materials, have received increasing attention recently owing to their various attractive properties such as fully spin-polarization and high carrier mobility. Based on their unique band structures, SGSs can be divided into two types: parabolic and Dirac-like linear. The linear-type SGSs, also called Dirac SGSs (DSGSs), have real massless fermions and dissipation-less transport properties, and thus are regarded as promising material candidates for applications in ultra-fast and ultra-low-power spintronic devices. DSGSs can be further classified into p-state type or d-state type depending on the degree of contribution of either the p-orbitals or d-orbitals to the Dirac states. Considering the importance of the research field and to cover its fast development, we reviewed the advances in DSGSs and proposed our own viewpoints. First, we introduced the computational algorithms of SGSs. Second, we found that the boundaries between DSGSs and Dirac half-metals were frequently blurred. Therefore, a simple classification is proposed in this work. Third, we collected almost all the studies on DSGSs published in the past six years. Finally, we proposed new guidance to search for DSGSs among 3D bulk materials on the basis of our latest results. [ABSTRACT FROM AUTHOR]

Fe3O4 with high Curie temperature and 100% spin polarization is a potential candidate for practical applications in flexible spintronics. In this work, combined with flexible muscovite substrates, the dynamic strain influenced Verwey transition of Fe3O4 has been studied. The Verwey transition temperature increases (decreases) in the inward (outward) bending heterostructures. From the analyses of Fe L2,3 edge X-ray absorption spectroscopy, the reversible modulation originates from the charge reconstruction effect with the valence variations of Fe ions on the tetrahedral site and octahedral site in different bending states. Meanwhile, the charge reconstruction effect enhances the net magnetic moments of the Fe3O4/muscovite heterostructures in bending states. [ABSTRACT FROM AUTHOR]

Interdot spin transfer dynamics is studied in a laterally coupled excited spin ensemble of high-density InGaAs quantum dots (QDs). We observe a rise time of the photoluminescence intensity of ∼100 ps and a simultaneous increase in the spin polarization of the excited spin ensemble, indicating spin injection from higher-energy levels in smaller QDs. Moreover, this coupled ensemble exhibits decay properties of the spin polarization that vary with the excited spin density. This phenomenon can be quantitatively understood by considering interdot spin transfer into lower-energy levels of the surrounding QDs, where the transfer rate depends on the degree of state filling of each QD level. [ABSTRACT FROM AUTHOR]

Spin-gapless semiconductors with their unique band structure have recently attracted much attention due to their interesting transport properties that can be utilized in spintronics applications. We have deposited the thin films of a quaternary spin-gapless semiconductor CoFeMnSi Heusler alloy on MgO (001) substrates using a pulsed laser deposition system. These films show epitaxial growth along the (001) direction and display a uniform and smooth crystalline surface. The magnetic properties reveal that the film is ferromagnetically soft along the in-plane direction and its Curie temperature is well above 400 K. The electrical conductivity of the film is low and exhibits a nearly temperature independent semiconducting behaviour. The estimated temperature coefficient of resistivity for the film is –7x10–10 Ωm/K, which is comparable to the values reported for spin-gapless semiconductors. [ABSTRACT FROM AUTHOR]

Heusler compounds are of interest as electrode materials for use in magnetic tunnel junctions (MTJs) due to their half metallic character, which leads to 100% spin polarization and high tunneling magnetoresistance. Most work to date has focused on the improvements to tunneling magnetoresistance that can stem from the use of Heusler electrodes, while there is much less work investigating the influence of Heusler electrodes on the spin transfer torque properties of MTJs. Here, we investigate the bias dependence of the anti-damping like and field-like spin transfer torque components in both symmetric (Co2MnSi/MgO/Co2MnSi) and asymmetric (Co2MnSi/MgO/CoFe) structure Heusler based MTJs using spin transfer torque ferromagnetic resonance. We find that while the damping like torque is linear with respect to bias for both MTJ structures, the asymmetric MTJ structure has an additional linear component to the ordinarily quadratic field like torque bias dependence and that these results can be accounted for by a free electron tunneling model. Furthermore, our results suggest that the low damping and low saturation magnetization properties of Heusler alloys are more likely to lead significant improvements to spin torque switching efficiency rather than their half metallic character. [ABSTRACT FROM AUTHOR]

We present a systematical study on the evolution of antiphase boundary (APB) densities in Fe3O4 films, which were prepared by pulsed laser deposition and post annealing at different temperatures. By measuring the electron-phonon coupling parameter and using Allen's formula, we evaluate the films' antiphase boundary densities, which show a decreasing tendency with increasing annealing temperature. Consequently, a 50% increase of spin polarization in Fe3O4 films is achieved, and a 110% increase of the magnetoresistance ratio was found in 900 °C annealed Fe3O4 films compared to the as-grown sample. This work could contribute to the effective manipulation of APB densities and spin polarization in Fe3O4 films, which is desirable for the application of spintronics devices based on Fe3O4 films. [ABSTRACT FROM AUTHOR]

Herein, we propose and provide evidence for the experimentally and theoretically promising route of exploring spintronics materials with high performance via a synthetic hybrid of half-metallic ferromagnet and diluted magnetic semiconductor. Crystalline and well-ordered [Co2FeGe/Ge(Mn)]n superlattice, which is free of secondary phase separation, were prepared by the hybridization of end members, Co2FeGe and Ge(Mn), using the molecular beam epitaxy technique. Besides comparable magnetic properties with respect to the Co2FeGe films, the superlattice sample exhibits superior properties in electric conductivity and spin polarization, thus enhancing in favor of the spin injection efficiency. These results demonstrate the high feasibility of spintronics materials with low saturation magnetization, small coercivity, high Curie temperature, and high spin injection efficiency through the proposed route in this work. [ABSTRACT FROM AUTHOR]

We report a first-principles study on the tunnel magnetoresistance (TMR) and spin-injection effi- ciency (SIE) through phosphorene with nickel electrodes under the mechanical tension and bending on the phosphorene region. Both the TMR and SIE are largely improved under these mechanical deformations. For the uniaxial tension (εy) varying from 0% to 15% applied along the armchair transport (y-)direction of the phosphorene, the TMR ratio is enhanced with a maximum of 107% at εy=10%, while the SIE increases monotonously from 8% up to 43% with the increasing of the strain. Under the out-of-plane bending, the TMR overall increases from 7% to 50% within the bending ratio of 0%-3.9%, and meanwhile the SIE is largely improved to around 70%, as compared to that (30%) of the flat phosphorene. Such behaviors of the TMR and SIE are mainly affected by the transmission of spin-up electrons in the parallel configuration, which is highly dependent on the applied mechanical tension and bending. Our results indicate that the phosphorene based tunnel junctions have promising applications in flexible electronics. [ABSTRACT FROM AUTHOR]

The spin selection of the topological boundary states (TBS) which are protected by the chiral-like symmetry in quantum anomalous Hall insulator (QAHI) can be used to construct a bifunctional spin detector (SD). Such device made of QAHIs in parallel with opposite chirality can divide an incoming spin-polarized current into two outgoing currents. The agreement between numerical and analytical calculation proves that the SD device functions as both spin filter and spin separator well in reflecting the spin polarization of source material from the ratio of two currents. The monotonic relation of spin polarization and current ratio suggests that using such kind of device, the spin polarization can be obtained directly. We also find that such device has a broad working energy region attributed by the TBS within the bulk gap. Combining with the result that the current ratio is barely dependent on the coupling between candidate materials and device, it is reasonable to apply this technique with a stable measuring accuracy. Furthermore, the features such as having simple geometry, being manipulated without external magnetic field, and the prospect of working at room temperature make this proposed device seem promising in developing future low-power-consumption spintronic device. [ABSTRACT FROM AUTHOR]

Half-metallic ferromagnetic (HMF) materials show high spin polarization and are therefore interesting to researchers due to their possible applications in spintronic devices. In these materials, while one spin sub band has a finite density of states at the Fermi level, the other sub band has a gap. Because of their high Curie temperature (TC) and tunable electronic structure, HMF Heusler alloys have a special importance among the HMF materials. Full Heusler alloys with the stoichiometric composition X2YZ (where X and Y are the transition metals and Z is a sp element) have the cubic L21 structure with four interpenetrating fcc sublattices. When each of these four fcc sublattices is occupied by different atoms (XX0YZ), a quaternary Heusler structure with different structural symmetries (space group F-43m, #216) is obtained. Recently, these equiatomic quaternary Heusler alloys (EQHAs) with 1:1:1:1 stoichiometry have attracted a lot of attention due to their superior magnetic and transport properties. A special class of HMF materials identified recently is known as spin gapless semiconductors (SGS). The difference in this case, compared with HMFs, is that the density of states for one spin band is just zero at the Fermi level, while the other has a gap as in the case of HMFs. Some of the reported SGS materials belong to EQHAs family. This review is dedicated to almost all reported materials belonging to EQHAs family. The electronic structure and hence the physical properties of Heusler alloys strongly depend on the degree of structural order and distribution of the atoms in the crystal lattice. A variety of experimental techniques has been used to probe the structural parameters and degree of order in these alloys. Their magnetic properties have been investigated using the conventional methods, while the spin polarization has been probed by point contact Andreev reflection technique. The experimentally obtained values of saturation magnetization are found to be in agreement with those estimated using the Slater-Pauling rule in most of the cases. Electrical resistivity and Hall measurements are being used to distinguish between SGS and HMF nature in detail. The current spin polarization value, P=0.70±0.01, for CoFeMnGe is found to be highest among the EQHAs. CoFeMnSi and CoFeCrGa are found to show SGS behavior with high Curie temperatures, thus making them suitable substitutes for diluted magnetic semiconductors. CoRuFeSi is found to have the highest TC among EQHAs. Theoretical prediction of magnetic properties on the basis of electronic structure calculations has also been reported in a few systems, which are also discussed in this review. Thus, this review presents a consolidated picture of the magnetic and spintronic properties of this important, but relatively new class of Heusler alloys. It is expected that this will stimulate further interest in these alloys, thereby paving the way for the identification of more HMF and SGS materials. As a result of this, it is expected that more efficient spintronic devices using these alloys would emerge in the near future. [ABSTRACT FROM AUTHOR]

Layered transition metal dichalcogenides (TMDs) have attracted extensive attention due to their interesting properties originating from an effective honeycomb lattice and strong spin-orbit coupling, and have potential applications in catalysis, lithium batteries, photonic, electronic, and valleytronic devices. Introducing magnetism in the TMDs can lead to the interesting functionalities such as magnetic order and carrier spin polarization with potential applications in spintronics. Here, we demonstrate an effective approach to induce robust ferromagnetism in MoS2 nanostructures by transition metal doping. After doping with a few percent Mn2+, the magnetism of MoS2 nanostructures is enhanced dramatically. Moreover, the magnetic properties are strongly temperature dependent, which is clearly different from the behavior of defect-induced magnetism. Our approach opens up the possibility for tuning the spin and magnetic properties in two-dimensional nanostructures. [ABSTRACT FROM AUTHOR]

The increasing interest in spin-based electronics has led to a vigorous search for new materials that can provide a high degree of spin polarization in electron transport. An ideal candidate would act as an insulator for one spin channel and a conductor or semiconductor for the opposite spin channel, corresponding to the respective cases of half-metallicity and spin-gapless semiconductivity. Our first-principle electronic-structure calculations indicate that the metallic Heusler compound Ti2MnAl becomes half-metallic and spin-gapless semiconducting if half of the Al atoms are replaced by Sn and In, respectively. These electronic structures are associated with structural transitions from the regular cubic Heusler structure to the inverted cubic Heusler structure. [ABSTRACT FROM AUTHOR]

We propose and investigate a spin modulator device consisting of two ferromagnetic leads connected by a two-dimensional topological insulator as the channel material. It exploits the unique features of the topological spin-helical edge states, such that the injected carriers with a noncollinear spin-polarization direction would travel through both edges and show interference effect. The conductance of the device can be controlled in a simple and all-electric manner by a side-gate voltage, which effectively rotates the spin-polarization of the carrier. At low voltages, the rotation angle is linear in the gate voltage, and the device can function as a good spin-polarization rotator by replacing the drain electrode with a non-magnetic material. [ABSTRACT FROM AUTHOR]

We propose a magnetic molecular junction consisting of a single-molecule magnet Fe4 connected two grapheneelectrodes and investigate transport properties, using the nonequilibrium Green's function method in combination with spin-polarized density-functional theory. The results show that the device can be used as a nearly perfect spin filter with efficiency approaching 100%. Our calculations provide crucial microscopic information how the four iron cores of the chemical structure are responsible for the spin-resolved transmissions. Moreover, it is also found that the device behaves as a highly efficient spin valve, which is an excellent candidate for spintronics of molecular devices. The idea of combining single-molecule magnets with graphene provides a direction in designing a new class of molecular spintronic devices. [ABSTRACT FROM AUTHOR]

Chromium dioxide (CrO2) is a half metal that is of interest for spintronic devices. It has not been synthesized through traditional physical vapor deposition (PVD) techniques because of its thermodynamic instability in low oxygen pressures. Epitaxial thin films of Ru doped tetragonal rutile CrO2 were synthesized by a PVD technique. The as-deposited RuxCr1-xO2 was ferrimagnetic with the saturation magnetization moment showing a strong dependence on the Ru concentration. Curie temperature as high as 241K has been obtained for ~23 at. % Ru. The Ru substitution increased the electrical conductivity by increasing the minority spin concentration. The spin polarization was found to be as high as 70% for 9 at.% Ru and decreased to ~60% with Ru concentrations up to ~44 at. %, which is determined by the Fermi velocities of the majority and minority spins. First principle calculations were performed to understand the effect of Ru content on the properties of CrO2. The PVD processes of Ru doped CrO2 could lead to the practical applications of the high spin polarization of CrO2 in spintronic devices. [ABSTRACT FROM AUTHOR]

Chromium dioxide (CrO2) is a half metal that is of interest for spintronic devices. It has not been synthesized through traditional physical vapor deposition (PVD) techniques because of its thermodynamic instability in low oxygen pressures. Epitaxial thin films of Ru doped tetragonal rutile CrO2 were synthesized by a PVD technique. The as-deposited RuxCr1-xO2 was ferrimagnetic with the saturation magnetization moment showing a strong dependence on the Ru concentration. Curie temperature as high as 241K has been obtained for ~23 at. % Ru. The Ru substitution increased the electrical conductivity by increasing the minority spin concentration. The spin polarization was found to be as high as 70% for 9 at.% Ru and decreased to ~60% with Ru concentrations up to ~44 at. %, which is determined by the Fermi velocities of the majority and minority spins. First principle calculations were performed to understand the effect of Ru content on the properties of CrO2. The PVD processes of Ru doped CrO2 could lead to the practical applications of the high spin polarization of CrO2 in spintronic devices. [ABSTRACT FROM AUTHOR]

Modern electronic devices utilize charge to transmit and store information. This leaves the information susceptible to external influences, such as radiation, that can introduce short timescale charge fluctuations and, long term, degrade electronic properties. Encoding information as spin polarizations offers an attractive alternative to electronic logic that should be robust to randomly polarized transient radiation effects. As a preliminary step towards radiation-resistant spintronic devices, we measure the spin properties of n-GaAs as a function of radiation fluence using timeresolved Kerr rotation and photoluminescence spectroscopy. Our results show a modest to negligible change in the long-term electron spin properties up to a fluence of 1×1014 (5MeV protons)/ cm², even as the luminescence decreases by two orders of magnitude. [ABSTRACT FROM AUTHOR]

Lasers in which spin-polarized carriers are injected provide paths to different practical room temperature spintronic devices, not limited to magnetoresistive effects. Unlike the conventional understanding of spintronic devices, an optimal performance of such spin-lasers can arise for finite, not infinite, spin relaxation time. By considering spin-relaxation times of both electrons and holes, we elucidate advantages of spin-lasers over their conventional (spin-unpolarized) counterparts. In addition to the steady-state threshold reduction, spin-lasers can improve transient operation leading to shorter turn-on delay times, reduced ringing of emitted light, and an enhanced bandwidth. [ABSTRACT FROM AUTHOR]

We investigate the microwave response of a spin transfer vortex based oscillator in a magnetic tunnel junction with an in-plane reference layer combined with a spin valve with an out-of-plane magnetization spin polarizing layer. The main advantage of this perpendicular spin polarizer is to induce a large spin transfer force even at zero magnetic field, thus leading to a record emitted power (up to 0.6 μW) associated to a very narrow spectral linewidth of a few hundreds of kHz. The characteristics of this hybrid vortex based spin transfer nano-oscillator obtained at zero field and room temperature are of great importance for applications based on rf spintronic devices as integrated and tunable microwave source and/or microwave detector. [ABSTRACT FROM AUTHOR]

We investigate the spin transport and precession in graphene by using the Hanle effect in nonlocal and three-terminal measurement geometries. Identical spin lifetimes, spin diffusion lengths, and spin polarizations are observed in graphene devices for both techniques over a wide range of temperatures. The magnitude of the spin signals is well explained by spin transport models. These observations rules out any signal enhancements or additional scattering mechanisms at the interfaces for both geometries. This validates the applicability of both the measurement methods for graphene based spintronics devices and their reliable extractions of spin parameters. [ABSTRACT FROM AUTHOR]

NiFe2O4(111) ultrathin films (3-5 nm) have been grown by oxygen-assisted molecular beam epitaxy and integrated as effective spin-filter barriers. Structural and magnetic characterizations have been performed in order to investigate the presence of defects that could limit the spin filtering efficiency. These analyses have revealed the full strain relaxation of the layers with a cationic order in agreement with the inverse spinel structure but also the presence of antiphase boundaries. A spin-polarization up to þ25% has been directly measured by the Meservey-Tedrow technique in Pt(111)/NiFe2O4(111)/γ-Al2O3(111)/Al tunnel junctions. The unexpected positive sign and relatively small value of the spin-polarization are discussed, in comparison with predictions and previous indirect tunnelling magnetoresistance measurements. [ABSTRACT FROM AUTHOR]

The CoFe thickness (tCoFe) dependence of spin injection efficiency was investigated for Co2MnSi/CoFe/n-GaAs junctions. The ΔVNL/I value, which is a measure of spin injection efficiency, strongly depended on tCoFe, where ΔVNL is the amplitude of a nonlocal spin-valve signal, and I is an injection current. Importantly, the maximum value of ΔVNL/I for a Co2MnSi/CoFe/n-GaAs junction was one order of magnitude higher than that for a CoFe/n-GaAs junction, indicating that a Co2MnSi electrode works as a highly polarized spin source. No clear spin signal, on the other hand, was observed for a Co2MnSi/n-GaAs junction due to diffusion of Mn atoms into the GaAs channel. Secondary ion mass spectrometry analysis indicated that the CoFe insertion effectively suppressed the diffusion of Mn into GaAs, resulting in improved spin injection properties compared with those for a Co2MnSi/n-GaAs junction. [ABSTRACT FROM AUTHOR]

Ni/EuS multilayers with excellent multilayer sequencing are deposited via e-beam evaporation on the native oxide of Si(100) wafers at 4 x 10-9 millibars. The samples have very small surface and interface roughness and show sharp interfaces. Ni layers are nanocrystalline 4-8 nm thick and EuS layers are 2-4 nm thick and are either amorphous or nanocrystalline. Unlike for Co/EuS multilayers, all Eu ions are in divalent (ferromagnetic) state. We show a direct antiferromagnetic coupling between EuS and Ni layers. At room temperature, the EuS layers are spin-polarized due to the proximity of Ni. Therefore, Ni/EuS is a candidate for room-temperature spintronics applications. [ABSTRACT FROM AUTHOR]

The spin lifetime and Hanle signal amplitude dependence on bias current has been investigated in insulating Al0.3Ga0.7As:Si using a three-terminal Hanle effect geometry. The amplitudes of the Hanle signals are much larger for forward bias than for reverse bias, although the spin lifetimes found are statistically equivalent. The spin resistance-area product shows a strong increase with bias current for reverse bias and small forward bias until 150 µA, beyond which a weak dependence is observed. The spin lifetimes diminish substantially with increasing bias current. The dependence of the spin accumulation and lifetime diminish only moderately with temperature from 5K to 30K.V [ABSTRACT FROM AUTHOR]

Spin-dependent transport through a ferromagnetic metal/organic-ferromagnet/ferromagnet metal junction is investigated theoretically. It is demonstrated that the current through the device strongly depends on the alignment of the magnetization orientations of the electrodes and interlayer. The spin-related electron tunnelling between the ferromagnetic electrodes suffers a further spin selection induced by the spin-polarized states of the central organic ferromagnet. This work indicates an intriguing prospect of organic ferromagnets in spintronic devices, such as four-state magnetoresistance manipulated by a magnetic field. [ABSTRACT FROM AUTHOR]

We demonstrate the electrical injection and detection of spin-polarized electrons in the Co2FeSi/GaAs hybrid system using lateral transport structures. Spin valve signatures and characteristic Hanle curves are observed both in the non-local and the local configuration. The comparatively large magnitude of the local spin valve signal and the high signal-to-noise ratio are attributed to the large spin polarization at the Fermi energy of Co2FeSi in the well-ordered L21 phase. [ABSTRACT FROM AUTHOR]

Non-zero spin polarization induced by optical orientation was clearly observed at room temperature in a Ge/Ge0.8Si0.2 quantum well grown on Ge and a Ge layer grown on Si by molecular beam epitaxy, whereas it was absent in bulk Ge. This occurred because indirect-gap photoluminescence (PL), which can obscure the spin-polarization information carried by the direct-gap PL, was quenched by unintentional growth-related defects in the epitaxial layers. Such interpretation was confirmed by applying time gating that effectively removed the indirect-gap PL characterized by a slower rise time, which allowed us to demonstrate the existence of room-temperature spin polarization in bulk Ge. [ABSTRACT FROM AUTHOR]

Spin-dependent transport through an endohedral fullerene Co@C60 dimer with gold electrodes is explored theoretically using density functional and extended Hückel theory. Density of states spin polarizations up to 95%, due to spin-splitting of Co 3d orbitals, are found by varying the gate and/or bias voltage. The current-voltage characteristics and strong (up to 100%) spin polarization of the current indicate that the device can be utilized for highly efficient spin injection into nonmagnetic conductors. This finding opens the way to the realization of electrostatically tuned spintronic nano devices less than 2 nm in size, without ferromagnetic electrodes. [ABSTRACT FROM AUTHOR]