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Spin pumping from canted antiferromagnets is a cutting-edge topic in modern spintronics. The interest for fundamental and applied research that these materials arouse is related to their unusual structure, namely, with a small canting of the magnetic sublattices, which is explained by the presence of the Dzyaloshinskii–Moriya interaction. Through this effect, it becomes possible to experimentally study quasi-ferromagnetic resonance spectra and spin pumping in the range of tens of GHz at room temperature. In this paper, an experimental and theoretical investigation of spin pumping from an antiferromagnet with weak ferromagnetism, α -Fe 2 O 3 , is carried out. The conversion of the precession of the magnetization vector, excited by an alternating magnetic microwave field, into a constant voltage is realized using the inverse spin Hall effect in the hematite/heavy metal structure. Using a constant magnetic field up to 5 kOe, the resonant frequency of such a detector is tunable over a wide range up to 32 GHz with potential sensitivity reaching 10.1 μ V/W. Confirmation of the measurement of the spin current is the change in the sign of V sp when the polarity of the constant magnetic field alters. We believe that these studies will make a major contribution to the understanding of the physics of the spin-pumping effect from antiferromagnets and will also help in the development of devices for quantum technologies and next-generation communication technologies. [ABSTRACT FROM AUTHOR]

Spin pumping from canted antiferromagnets is a cutting-edge topic in modern spintronics. The interest for fundamental and applied research that these materials arouse is related to their unusual structure, namely, with a small canting of the magnetic sublattices, which is explained by the presence of the Dzyaloshinskii–Moriya interaction. Through this effect, it becomes possible to experimentally study quasi-ferromagnetic resonance spectra and spin pumping in the range of tens of GHz at room temperature. In this paper, an experimental and theoretical investigation of spin pumping from an antiferromagnet with weak ferromagnetism, α -Fe 2 O 3 , is carried out. The conversion of the precession of the magnetization vector, excited by an alternating magnetic microwave field, into a constant voltage is realized using the inverse spin Hall effect in the hematite/heavy metal structure. Using a constant magnetic field up to 5 kOe, the resonant frequency of such a detector is tunable over a wide range up to 32 GHz with potential sensitivity reaching 10.1 μ V/W. Confirmation of the measurement of the spin current is the change in the sign of V sp when the polarity of the constant magnetic field alters. We believe that these studies will make a major contribution to the understanding of the physics of the spin-pumping effect from antiferromagnets and will also help in the development of devices for quantum technologies and next-generation communication technologies. [ABSTRACT FROM AUTHOR]

Investigating the interplay between charge and spin conversion in two-dimensional (2D) materials holds significant promise for futuristic electronic applications. Through density functional theory, our study delves into the charge-spin conversion and spin density dynamics in the non-magnetic SnNBr monolayer under time-reversal invariance. The breaking of out-of-plane mirror symmetry and inversion symmetry, along with the presence of spin–orbit coupling (SOC) lead to a notable momentum-dependent spin band splitting or Rashba effect induced by the inherent out-of-plane electric field. Theoretical calculations reveal not only the presence of profound Rashba spin splitting but also the coexistence of intrinsic spin Hall effects in the SnNBr monolayer. Analysis of k-resolved spin Berry curvature sheds light on the origin of the substantial intrinsic spin Hall conductivity. Furthermore, our research highlights the modulation of charge-to-spin conversion and spin density accumulation through in-plane biaxial strains. Moreover, the variation in the Rashba parameter is correlated with the changes in the built-in out-of-plane electric field and microscopic atomic orbital contributions. These findings underscore the exceptional potential of the non-centrosymmetric SnNBr monolayer for advanced spintronics, spin-orbitronics, and piezo-spintronic applications, and serve as a catalyst for further experimental investigations. [ABSTRACT FROM AUTHOR]

The combined influence of spin–orbit coupling and spatial inversion asymmetry leads to an enhancement of electronic properties, including Rashba spin-splittings as well as spin Hall effect. Recent research has shown the possibility to create two-dimensional Janus materials with inherent structural asymmetry. In this work, the structural stability, piezoelectricity, electronic properties, and intrinsic spin Hall conductivity of quintuple-layer atomic Janus Sb2XSX' (X, X' = S, Se, Te; X ≠ X') monolayers are investigated using first-principles calculations within the framework of density functional theory. They demonstrate relatively high in-plane piezoelectric coefficients ( d 22) and also possess out-of-plane piezoelectric coefficients ( d 31), which is due to the breaking of inversion symmetry in the crystal structure with the space group P3m1. Large Rashba parameters are obtained in Janus Sb2XSX' monolayers, especially high for Sb 2 S 2 Te (1.62 eV Å) and Sb 2 SeSTe (1.33 eV Å) due to strong spin–orbit coupling. Moreover, Rashba-like spin-splitting is also observed in the edge-states as well, which is highest for Sb 2 SeSTe with 2.17 eV Å. Furthermore, Sb 2 S 2 Te and Sb 2 SeSTe monolayers reveal a significantly high Berry curvature (65.59 and 61.05 Bohr 2), spin Berry curvature (− 118.4 and − 120.6 Bohr 2), and spin Hall conductivity (1.8 and 1.6 e 2 /h). Our results suggest that Janus Sb 2 S 2 Te and Sb 2 SeSTe monolayers could be an excellent platform for multifunctional electronic applications. [ABSTRACT FROM AUTHOR]

The photonic spin Hall effect has attracted considerable attention for its potential applications in precision metrology and spin-based photonics. However, the spin-dependent transverse shift arising from this phenomenon is considerably weak and poses a challenge in terms of detection. Here, we present a novel technique to amplify the photonic spin Hall effect by exciting the optical Tamm states through an Au-distributed Bragg reflector. Our approach involves optimizing the thickness of the Au layer and the spacing layer, as well as adjusting the Fermi energy of graphene. The result is a remarkable transverse shift of up to 18 μm in the horizontal polarization state. Furthermore, we introduce graphene into the Au-distributed Bragg reflector to enable dynamic control of the photonic spin Hall effect by manipulating the Fermi energy of graphene. These findings represent an innovative platform for enhancing and actively controlling the photonic spin Hall effect with significant potential for spin-controlled optics. [ABSTRACT FROM AUTHOR]

The recent discovery of inherently stable two-dimensional (2D) transition-metal dichalcogenides (TMDs) provides a unique platform for spintronic devices. However, its efficacy for electric detection by spin Hall magnetoresistance (SMR) has not been established yet. In this work, we report on SMR in 2D TMDs/ferromagnet heterostructures, i.e., PtSe 2 /NiFe (Py), whose magnitude reaches the maximum with bilayer PtSe 2. Notably, the SMR value in bilayer PtSe 2 /Py heterostructures undergoes a sign change with increasing Py thickness. For thinner Py samples, the SMR rapidly decreases with increasing Py thickness, eventually changing from positive to negative. In the case of intermediate Py thicknesses, the SMR consistently exhibits negative behavior. However, for thicker Py samples, the negative SMR values gradually decrease. This complex behavior is attributed to the dominant and competing mechanisms that contribute to SMR, including the spin Hall effect (or Rashba-induced effect) and its inverse effect, the orbital Hall effect and its inverse effect, as well as interfacial spin–orbit-coupling-induced spin-current-to-charge-current conversion. These findings would expand the arsenal for advanced spintronic applications based on 2D TMDs. [ABSTRACT FROM AUTHOR]

We investigate the photonic spin Hall effect of a linearly polarized Gaussian beam reflected on the surface of twisted bilayer phosphorene. The photonic spin shift depends strongly on optical resonance behavior, which is determined by the twist angle. The magnified spin shift near the Brewster angle is sensitive to the twist angle and can be fitted by numerical models. In particular, the spin shifts in the terahertz region of frequency are well within the current experimental detection precision. Our findings suggest that the photonic spin Hall effect is promising for precise characterization of the optical property and the structure of twisted bilayer phosphorene. [ABSTRACT FROM AUTHOR]

Thin layers of ferromagnetic/non-magnetic bimetallic heterostructures have become the focal point of spintronics, primarily due to their capacity to convert spin to charge current, leveraging the spin- and inverse spin Hall effects. However, the interfacial properties and morphologies can significantly influence this conversion. Hence, we employed molecular dynamics calculations to model the construction of the Fe/Pt interface at various bilayer growth temperatures and Pt deposition rates. We then experimentally evaluated the modeling using x-ray methods to resolve the chemical and structural state of the interface. The calculations revealed moderate diffusive phenomena between the adjacent layers and an interfacial roughness of less than 1 nm, consistent with the experimental observations. In cases where plastic relaxation of the Fe/Pt interface is insufficient, lattice deformation is mitigated by a local pseudomorphic growth caused by transformation of the Pt crystal symmetry. Additionally, interfacial planar defects may emerge as a complementary stress-relieving mechanism to misfit dislocations. By combining the experimental and computational findings, we propose optimized growth conditions for an "ideal" Fe/Pt interface, which could serve as a useful tool to control the efficiency of spin-to-charge conversion. [ABSTRACT FROM AUTHOR]

In this work, we study the electronic properties of nanotubes with spin–orbit interaction that exhibit a spin Hall effect. Nanoribbons made of these materials are expected to have topologically protected states. The lack of edge states in a seamless tube eliminates the possibility of finding a topological edge state. The spin–orbit interaction breaks the degeneracy of Dirac's cones and eliminates the chance of finding a metal nanotube. As a consequence, this makes all nanotubes with spin–orbit interaction trivial band insulators. We focus our attention on two features. First, we study the energy band gap as a function of the diameter of the nanotubes. Then, we concentrate on controlling the bandgap of a nanotube by applying an external radial electric field. Finally, we discuss the possibility of using one of these tubes as a field-effect transistor. [ABSTRACT FROM AUTHOR]

Photonic spin Hall effect (PSHE) of the transmitted wave presents promising applications in photonic spintronic devices, including inter-chip optical circuitry and quantum computing devices. These applications can benefit from phenomena such as the photon tunneling effect, frustrated total internal reflection, and the resonant optical tunneling effect. However, the mechanisms for enhancing PSHE of the transmitted wave are limited. In this study, an alternative strategy is proposed, which involves the utilization of topological edge states to enhance PSHE without relying on the aforementioned means. To demonstrate this effect, a heterostructure is designed, comprising two one-dimensional photonic crystals (PhCs) and a monolayer graphene. By leveraging the topological edge state, a significant enhancement of PSHE in the transmitted wave is observed, surpassing several times the incident wavelength. Furthermore, it is shown that the enhanced PSHE can be controlled and fine-tuned by adjusting the Fermi energy of monolayer graphene and the repetition numbers of the two PhCs. The enhanced and controlled PSHE in this heterostructure introduces possibilities for the development of novel optical components, such as switches, filters, modulators, and sensors. [ABSTRACT FROM AUTHOR]

We study the W/Cu multilayers as a spin current source and the coherent spin–orbit torques in a Fe layer using the spin-torque ferromagnetic resonance (STFMR) technique. With increasing numbers of layers, the line shape of the STFMR signals changes from predominantly antisymmetric to predominantly symmetric. When using [W(0.5)/Cu(0.5)]5 as a spin current source, the symmetric amplitude increases by a factor of 5 compared to a single W layer. Simultaneously, the effective damping parameter also increases slightly due to enhanced spin pumping. Along with an increasing trend in the damping-like torque efficiency, this suggests that the extrinsic spin Hall effect is enhanced. Concurrently, the antisymmetric amplitude decreases significantly by a factor of 27, which indicates an increase in the field-like torque when multilayers are used as a spin current source. [ABSTRACT FROM AUTHOR]

Here, we report a photonic spin Hall effect (PSHE), i.e., splitting of opposite spin in a transverse direction using a multi-layered metallo-dielectric heterostructure by hybridization of a Tamm plasmon polariton and a surface plasmon polariton. The underlying mechanism of PSHE is also explained using the concept of superposition of normal and abnormal modes in the circular-polarization basis. It is revealed that the spin-dependent transverse shift for the proposed hybrid structure is enormously high owing to the transverse shift of ∼18 μm. The PSHE is found to be strongly dependent on the number of bi-layers of the structure and the analyte refractive index, which provides an additional degree of freedom for tailoring the device performance. Therefore, this study opens a pathway for developing next-generation photonic spin Hall devices in the fields of spin photonics, optical sensing, and optical communications. [ABSTRACT FROM AUTHOR]

We investigate the spin Hall effect in a single-layer graphene device with disorder and interface-induced spin–orbit coupling. Our graphene device is connected to four semi-infinite leads that are embedded in a Landauer–Büttiker setup for quantum transport. We show that the spin Hall angle of graphene devices exhibits mesoscopic fluctuations that are similar to metal devices. Furthermore, the product between the maximum spin Hall angle deviation and dimensionless longitudinal conductivity follows a universal relationship Θ s H × σ = 0.18. Finally, we compare the universal relation with recent experimental data and numerically exact real-space simulations from the tight-binding model. [ABSTRACT FROM AUTHOR]

We present a detailed investigation of spin pumping from full Heusler compound Co2FeSi (CFS) to single-layer two-dimensional (2D) transition metal dichalcogenide (TMD) MoS2 (molybdenum disulfide) excited by ferromagnetic resonance. Microwave-induced spin pumping has been identified by a significant enhancement of Gilbert damping in Si/SiO2/MoS2/CFS heterostructures as compared to bare Si/SiO2/CFS samples. The CFS thickness dependent spin mixing conductance indicates an efficient spin transparent interface of MoS2/CFS. In addition, the spin-to-charge conversion process has been quantified using inverse spin Hall effect (ISHE) measurements. In ISHE measurements, a highly symmetric Lorentzian DC voltage signal in Si/SiO2/MoS2/CFS heterostructures is observed in comparison with a highly asymmetric signal in bare Si/SiO2/CFS samples, establishing a clear sign of FMR induced spin pumping. The results in this work are expected to aid in the understanding of the spin angular momentum transfer phenomenon at the interface of the 2D TMDs/ferromagnet bilayer system. [ABSTRACT FROM AUTHOR]

We present a detailed investigation of spin pumping from full Heusler compound Co2FeSi (CFS) to single-layer two-dimensional (2D) transition metal dichalcogenide (TMD) MoS2 (molybdenum disulfide) excited by ferromagnetic resonance. Microwave-induced spin pumping has been identified by a significant enhancement of Gilbert damping in Si/SiO2/MoS2/CFS heterostructures as compared to bare Si/SiO2/CFS samples. The CFS thickness dependent spin mixing conductance indicates an efficient spin transparent interface of MoS2/CFS. In addition, the spin-to-charge conversion process has been quantified using inverse spin Hall effect (ISHE) measurements. In ISHE measurements, a highly symmetric Lorentzian DC voltage signal in Si/SiO2/MoS2/CFS heterostructures is observed in comparison with a highly asymmetric signal in bare Si/SiO2/CFS samples, establishing a clear sign of FMR induced spin pumping. The results in this work are expected to aid in the understanding of the spin angular momentum transfer phenomenon at the interface of the 2D TMDs/ferromagnet bilayer system. [ABSTRACT FROM AUTHOR]

The enhanced photonic spin Hall effect was previously possible only for the horizontal polarization (H-polarized) in plasmonic systems. The wave-guiding surface plasmonic resonance (SPR) effect is used to report a giant photonic spin Hall effect (G-PSHE) of reflected light for horizontal and vertical polarized waves. This novel work investigated the polarization-manipulated G-PSHE in the modified Kretschmann configuration with an additional glass dielectric thin wave-guiding layer. The ultrathin gold layer and an additional dielectric wave-guiding layer are responsible for achieving millimeter-scale (more than 2 mm to submillimeter) G-PSHE. With this novel approach, polarization manipulation is achieved by employing wave-guiding and the SPR effect. Using a finite element method based simulation study, the impact of an additional thin dielectric wave-guiding layer on G-PSHE is investigated. This study enables the potential application of both horizontal and vertical polarization-based quantum devices and sensors for which light spin plays a pivotal role. [ABSTRACT FROM AUTHOR]

We investigated the ferromagnet (FM) and heavy metal (HM) thickness dependence of the electric current-induced spin orbit torque (SOT), especially the field-like (FL) torque component in HM/CoFeB/MgO heterostructures. For Pt/CoFeB/MgO and Ta/CoFeB/MgO structures, after subtracting the dead-layer thickness of CoFeB, the damping-like (DL) effective field follows 1/tFM dependence, while the FL effective field deviates from 1/tFM dependence at the ultra-thin FM thickness range, indicating that an extra origination of FL torque, i.e., spin backflow at the FM/MgO interface, is responsible for the large FL torque in HM/CoFeB/MgO structures with a ultra-thin CoFeB layer. For Ta/Pt(tPt)/CoFeB(1)/MgO structures, the FL-SOT exhibits a gradual change similar to the DL-SOT, suggesting that the spin Hall effect is the dominant origination of spin current, which enhances the FL-SOT in the HM/CoFeB/MgO structures by the spin backflow effect when tCoFeB is less than the spin dephasing length. We also demonstrated that the obvious dead-layer thickness at the Ta/CoFeB interface reduces the effective CoFeB thickness and enhances the spin backflow effect further. [ABSTRACT FROM AUTHOR]

In this work, we theoretically study the magnon spin transport in easy-plane antiferromagnetic insulators in the presence of an in-plane magnetic field. By exactly calculating the magnon spectrum, we find that the band splitting due to magnetic anisotropy can be fully compensated by the external field at a particular strength, which makes the dynamics nearly equivalent to an easy-axis antiferromagnet. As a result, the intrinsic magnon spin Hall effect due to the dipole–dipole interaction, previously predicted in easy-axis antiferromagnets, is activated in easy-plane antiferromagnets. The compensation feature also allows the field control of magnon spin lifetime and hence the spin diffusion length. The compensation feature is robust against biaxial anisotropy. [ABSTRACT FROM AUTHOR]

Spin–orbit torques (SOTs) generated by in-plane current injection in a ferromagnetic metal (FM)/heavy metal (HM) bilayer offers a new route to electrically manipulate magnetization. Here, we report on two sizable spin–orbit field contributions from the spin Hall effect and Rashba effect in NiFe/W bilayers by using the planar Hall effect. Both spin–orbit fields decrease with increasing W layer thickness. Importantly, the spin–orbit field contributing from the spin Hall effect decreases faster than the one from the Rashba effect as the thickness of W layer increases, leading to the sign change of the field-like torque at thicker W. Our results illustrate the co-contributions of the Rashba effect and the spin Hall effect to the field-like SOT in NiFe/W bilayer giving more insight into the effect of the field-like SOT in a FM/HM bilayer. [ABSTRACT FROM AUTHOR]

Charge–spin interconversion provides an effective way to generate spin current, spin–orbit torque, and unconventional magnetoresistance that is different from the magnetoresistance originated from spin-polarized current. A widely studied system that leads to all these phenomena is the ferromagnet/heavy metal bilayer, in which spin accumulation/current is generated through either the spin Hall effect in the heavy metal layer or Rashba–Edelstein effect at the ferromagnet/heavy metal interface. The subsequent interaction of the current-induced spins with the ferromagnet generates spin–orbit torque, and the inverse conversion of the backflow spin current to charge current in the heavy metal layer leads to different types of magnetoresistances. Many proof-of-concept devices and applications have been demonstrated based on the spin–orbit torque and magnetoresistance in the bilayer system, including non-volatile memory, logic, nano-oscillator, magnetic sensor, neuromorphic and scholastic computing, etc. In addition to the bilayer systems, recently there is also a growing interest in charge–spin interconversion in single-layer ferromagnets. In this Perspective, we first introduce the charge–spin interconversion in different systems based on phenomenological models, after which we show how the spin–orbit torque and spin Hall magnetoresistance in ferromagnet/heavy metal bilayers can be exploited for magnetic sensing applications. We also discuss charge–spin interconversion in single-layer ferromagnets via the anomalous Hall effect. [ABSTRACT FROM AUTHOR]

Spin–orbit torque that originates from spin Hall effect and Dzyaloshinskii–Moriya interaction (DMI) can efficiently move chiral magnetic domain walls in perpendicularly magnetized wires. It has been shown that antiferromagnetically coupled composite domain walls across a ruthenium layer can be driven even faster by exchange coupling torque that is proportional to exchange coupling strength. Here, we report a current-driven motion of composite chiral domain walls in synthetic antiferromagnets with a rhodium spacer layer. It is found that the domain walls in the wire with a rhodium layer do not move as fast as that with a ruthenium layer although the exchange coupling in Co|Rh|Co is stronger than Co|Ru|Co, which is due to the formation of a large DMI at the Rh|Co interface. The Dzyaloshinskii–Moriya interaction at the Co/Rh interface has the same sign and comparable strength to the Pt|Co interface, thus negating the exchange coupling torque. The spin Hall effect from rhodium is found to be as small as ruthenium. Our findings show that rhodium can be used to tailor the DMI strengths in the current-driven motion of chiral domain walls in various magnetic nanostructures. [ABSTRACT FROM AUTHOR]

Efficient spin-charge conversion is indispensable in spintronic computing and memory technologies for achieving low power. Spin Hall and quantum spin Hall effects have been demonstrated in certain atomically thin two-dimensional (2D) materials. In this work, we develop a multiscale simulation method from atomistic quantum transport simulation to the circuit model for the spin Hall effect (SHE) device based on 2D materials. Numerical implementation to speed up atomistic transport simulations with the non-equilibrium Green's function formalism is described for the crossbar SHE device. The multiscale method can treat atomistic scale features and compute the spintronic device performance metrics of the modeled device. As an example, the effect of edge roughness on the SHE devices based on monolayer 2D materials is investigated. The results illustrate that aggressively scaled monolayer SHE devices can efficiently transduce charge to spin in the presence of edge roughness. [ABSTRACT FROM AUTHOR]

Monolayer transition metal dichalcogenides have strong spin–orbit coupling and broken space inversion symmetry, which enable them to be the key building blocks in realizing spin and valley-related effects. Here, we report the spin and valley Hall conductivities of monolayer transition metal dichalcogenides in the presence of the magnetic proximity effect, which is introduced by a ferromagnetic substrate. It is found that the profile and magnitude of the spin and valley Hall conductivities in monolayer transition metal dichalcogenides are different with and without magnetic exchange interactions. This difference can be attributed to the asymmetrical band structure of monolayer transition metal dichalcogenides and chemical potential-dependent interband transitions. The former comes from the fact that the magnetic proximity effect can effectively break the time reversal symmetry and thus lead to the asymmetry of the band structures between K + and K − valleys, which causes the final changes in the spin and valley Hall conductivities. Our findings demonstrate that the magnetic proximity effect can affect the spin as well as valley Hall behaviors in monolayer transition metal dichalcogenides, and this strategy is applicable for other two-dimensional layered materials, which is promising for spintronic and valleytronic devices. [ABSTRACT FROM AUTHOR]

The unidirectional spin Hall magnetoresistance (USMR) is one of the most complex spin-dependent transport phenomena in ferromagnet/nonmagnet bilayers, which involves spin injection and accumulation due to the spin Hall effect, spin-dependent scattering, and magnon scattering at the interface or in the bulk of the ferromagnet. While USMR in metallic bilayers has been studied extensively in very recent years, its magnitude (∼10−5) is too small for practical applications. Here, we demonstrate a giant USMR effect in a heterostructure of BiSb topological insulator – GaMnAs ferromagnetic semiconductors. We obtained a large USMR ratio of 1.1% and found that this giant USMR is governed not by the giant magnetoresistancelike spin-dependent scattering but by magnon emission/absorption and strong spin-disorder scattering in the GaMnAs layer. Our results provide new insights into the complex physics of USMR, as well as a strategy for enhancing its magnitude for device applications. [ABSTRACT FROM AUTHOR]

Spin Hall magnetoresistance (SMR) provides an effective tool to probe the spin structure in magnet/heavy metal bilayers. Here, we investigate the SMR in Gd3Fe5O12 (GdIG)/Pt bilayers, where GdIG is a compensated ferrimagnetic insulator. Under a finite magnetic field, GdIG has a collinear magnetic phase far away from compensated temperature (Tcomp) and noncollinear/canted magnetic phase around Tcomp of 278 K. A conventional SMR behavior is observed at different temperatures without any sign change around Tcomp. Meanwhile, an asymmetric behavior (unidirectional-like) exists in the observed SMR at the temperatures just above or below Tcomp, because of the contribution of the anisotropic magnetothermopower effect, i.e., spin Seebeck effect. The spin Seebeck effect component exhibits a sign change around Tcomp, which is correlated with the reversal of the sublattice magnetization. Our finding provides an insight into SMR and thermal spin transport in the GdIG/Pt bilayer structure. [ABSTRACT FROM AUTHOR]

Realization of the Inverse Spin Hall Effect (ISHE) with hot electrons in direct bandgap semiconductors is an intriguing puzzle. Here, we report the influence of steady state carrier accumulation in the satellite L valley on the establishment of ISHE in the GaAs epilayer. Steady state carrier accumulation is calculated by analytically solving the rate equations where the whole conduction band is divided into four distinct regions based on the energy and momentum. Electron-hole generation, energy and spin relaxation, and various recombination mechanisms are considered in the theoretical framework where carrier accumulation in the L valley of GaAs is driven by intervalley scattering. This is then followed by a set of experiments to measure the photoinduced ISHE at excitation energy (Eex) of 1.65, 1.94, and 2.33 eV, where significant differences are theoretically predicted. The measured values of ISHE signal are thereafter compared with the numerically calculated ones, which establish the validity of the proposed formalism. Further, the physical origin of ISHE signal is investigated for different regimes that lead to the observation of intervalley scattering induced ISHE at Eex = 2.33 eV. [ABSTRACT FROM AUTHOR]

A ferrimagnet (FiM) has small domains consisting of oppositely polarized and unequal magnetic moments. Oppositely polarized magnetic moments have strong exchange coupling between them resulting in robust torque in FiM called bulk torque. Due to the strong bulk torque, magnetic moments in FiM do not precess around the switching axis for a long time unlike ferromagnets (FMs) leading to faster switching speed compared to FM. In this paper, we propose and model the switching of FiM (CoTb) with spin current injection from heavy metal with strong spin Hall effect (SHE) such as Pt. We carry out ab initio calculation of the Dzyaloshinskii-Moriya interaction (DMI) at the FiM(CoTb)/heavy metal(Pt) interface using spin polarized relativistic Korringa-Kohn-Rostoker (KKR) Green's function method. We compute the exchange coupling among the magnetic moments inside the CoTb layer and model how the spin-orbit torque (SOT) along with the bulk torque can efficiently switch the FiM. Then, we consider a ferrimagnet based magnetic tunnel junction (FMTJ) with SHE metal. We perform a comprehensive simulation and performance analysis of FiM(CoTb)/MgO/CoFeB and FiM(CoTb)/MgO/FiM(CoTb) FMTJs with Pt underlayer. Using non-equilibrium Green's function (NEGF) formalism, we calculate the tunneling magnetoresistance (TMR) of the proposed FMTJs at room temperature. Furthermore, the importance of thickness in CoTb magnetization dynamics is shown using our FiM magnetization simulation framework. We analyze and show that the CoTb based FMTJ has large switching energy barrier to ensure thermal stability. Finally, we show the performance comparison (TMR, write performance and power consumption) between our proposed FMTJs and FM based MTJ and our simulation exhibits that for picosecond range switching speed, FMTJ is ∼ 25 times more energy efficient than FM based MTJ. [ABSTRACT FROM AUTHOR]

The fullerene C60, C70, and C84 molecules, that are composed of ∼99% naturally abundant 12C having spinless nuclei, are considered to have miniature hyperfine interaction and also weak intrinsic spin-orbit coupling (SOC) due to the light carbon atoms. However, it has been theoretically predicted that the curvature of the fullerene molecules may increase the SOC due to the induced hybridization of the π and σ electrons on the carbon atoms that reside on the fullerene molecule surface. In this work, we have measured the spin diffusion length in films of C60, C70, and C84 in NiFe/fullerene/Pt trilayer devices, where pure spin current is injected into the fullerene film at the NiFe/fullerene interface via spin pumping induced by microwave absorption at ferromagnet resonance conditions, and subsequently detected at the fullerene/Pt interface as electrical current via the inverse spin-Hall effect. The obtained spin diffusion lengths in the fullerene films are of the order of 10 nm and increase from C60 to C84 in which the fullerene molecule's curvature decreases; this finding validates the existence of curvature-induced SOC in the fullerenes. Our results deepen the understanding of spin transport in fullerene films and may benefit the design of molecular spintronic devices. [ABSTRACT FROM AUTHOR]

Current-induced magnetization reversal due to spin-orbit torque is demonstrated in an anisotropy controlled Pt/Co/Pt trilayer. The samples were designed to have weak perpendicular magnetic anisotropy, with a measured anisotropy field of (1340 ± 20) Oe. Reversal is shown to be dominated by a damping-like torque associated with the spin-Hall effect. A small in-plane magnetic field was required to break the symmetry and enable reversal. With a 273 Oe field, magnetization reversal occurred with a current density amplitude of only 5 × 10 10 A m − 2 , which is shown to be consistent with a simple model. The field-like torque is negligible, so measurements indicate that the imaginary part of the spin-mixing conductance associated with Co/Pt interfaces must be negligible. [ABSTRACT FROM AUTHOR]

The photo-induced inverse spin Hall effect (ISHE) experiments are conducted in heavily doped n-GaAs epitaxial layers by measuring the transverse electric current generated through the diffusion of optically injected spin orientations over a temperature range of 10–300 K. ISHE origin of the measured signal is confirmed through meticulous checks including the characteristic dependence of magnitude of signal on the angle of incidence. The measured value of ISHE current (IISHE) is observed to fall with the increase in temperature. Furthermore, the value of spin current density is theoretically estimated by solving the spin diffusion equation with appropriate boundary conditions for an epitaxial layer. It is shown that by near resonant excitation and subsequent solution of diffusion equation, the spin Hall angle (γ) and spin Hall conductivity (σSH) can be estimated, provided the effective life time of spin polarized electrons(τS) is known independently. By using the numerically calculated value of τS, the proposed method is implemented to estimate the values of γ and σSH. It is found that the fall in the values of IISHE at high temperatures is not governed by σSH, rather by a rapid decrease in the values of τS. In fact, σSH is seen to increase with the temperature, which is compared with existing literature. The present work provides the necessary insight into material parameters which are essential for the development of advanced spin-photonic semiconductor devices. [ABSTRACT FROM AUTHOR]

We show that the photon energy dependence of the photo-induced inverse spin-Hall effect (ISHE) signal at Pt/semiconductor junctions can be reproduced by a model that explicitly accounts for the electron spin diffusion length Ls in the semiconductor. In particular, we consider the Pt/GaAs, Pt/Ge, and Pt/Si systems: although optical spin injection and transport of spin-polarized electrons in the conduction band of these semiconductors are ruled by different mechanisms, a simple one dimensional analytical diffusion model, where Ls is the free parameter, can reproduce the ISHE data in all cases. This highlights the potentialities of the photo-induced ISHE spectra as a tool to directly address fundamental spin transport properties in semiconductors. [ABSTRACT FROM AUTHOR]

In order to enhance the magnitude of spin-orbit torque (SOT), considerable experimental works have been devoted to studying the thickness dependence of the different layers in multilayers consisting of heavy metal (HM), ferromagnet (FM), and capping layers. Here, we present a theoretical model based on the spin-drift-diffusion formalism to investigate the effect of the capping layer properties such as its thickness on the SOT observed in experiments. It is found that the spin Hallinduced SOT can be significantly enhanced by incorporating a capping layer with an opposite spin Hall angle to that of the HM layer. The spin Hall torque can be maximized by tuning the capping layer thickness. However, in the absence of the spin Hall effect (SHE) in the capping layer, the torque decreases monotonically with the capping layer thickness. Conversely, the spin Hall torque is found to decrease monotonically with the FM layer thickness, irrespective of the presence or absence of the SHE in the capping layer. All these trends are in correspondence with experimental observations. Finally, our model suggests that capping layers with a long spin diffusion length and high resistivity would also enhance the spin Hall torque. [ABSTRACT FROM AUTHOR]

The spin-Hall effect induced modification of the attenuation of propagating exchange-mode spin waves (SWs) is studied micromagnetically and analytically in heavy-metal/ferromagnet bilayers. Micromagnetic simulations of spin-wave propagation in Pt/NiFe show that at a relatively low current density of ~6×1011 A/m2, Gilbert damping is exactly balanced by the spin-Hall torque and long-distance SW transmission is possible. An analytical model is developed to explain the micromagnetic results and relate the current density to the characteristic attenuation length. The results suggest that the spin Hall effect can be used as an effective means to control the attenuation length of propagating spin waves in nanostructures. [ABSTRACT FROM AUTHOR]

An electric method for measuring magnetic anisotropy in antiferromagnetic insulators (AFIs) is proposed. When a metallic film with strong spin-orbit interactions, e.g., platinum (Pt), is deposited on an AFI, its resistance should be affected by the direction of the AFI Néel vector due to the spin Hall magnetoresistance (SMR). Accordingly, the direction of the AFI Néel vector, which is affected by both the external magnetic field and the magnetic anisotropy, is reflected in resistance of Pt. The magnetic field angle dependence of the resistance of Pt on AFI is calculated by considering the SMR, which indicates that the antiferromagnetic anisotropy can be obtained experimentally by monitoring the Pt resistance in strong magnetic fields. Calculations are performed for realistic systems such as Pt/Cr2O3, Pt/NiO, and Pt/CoO. [ABSTRACT FROM AUTHOR]

Recently, we have demonstrated the presence of spin-orbit torque in FeMn/Pt multilayers which, in combination with the anisotropy field, is able to rotate its magnetization consecutively from 0° to 360° without any external field. Here, we report on an investigation of the static and dynamic magnetic properties of FeMn/Pt multilayers using the combined techniques of magnetometry, ferromagnetic resonance, inverse spin Hall effect, and spin Hall magnetoresistance measurements. The FeMn/Pt multilayer was found to exhibit ferromagnetic properties, and its temperature dependence of saturation magnetization can be fitted well using a phenomenological model by including a finite distribution in Curie temperature due to subtle thickness variations across the multilayer samples. The non-uniformity in static magnetic properties is also manifested in the ferromagnetic resonance spectra, which typically exhibit a broad resonance peak. A damping parameter of around 0.106 is derived from the frequency dependence of ferromagnetic resonance linewidth, which is comparable to the reported values for other types of Pt-based multilayers. Clear inverse spin Hall signals and spin Hall magnetoresistance have been observed in all samples below the Curie temperature, which corroborate the strong spin-orbit torque effect observed previously. [ABSTRACT FROM AUTHOR]

We have investigated dc voltage generation induced by ferromagnetic resonance in a Co75Fe25/Pt film. In order to reduce rectification effects of anisotropic magnetoresistance and the planar Hall effect, which may be observed simultaneously with the inverse spin Hall effect, we selected Co75Fe25 with extremely small anisotropic magnetoresistance as a spin injector. Using the difference in the spectral shape of voltage and in the angle dependence of in-plane magnetization among the effects, we demonstrated that the generated dc voltage is governed by the inverse spin Hall effect induced by spin pumping. [ABSTRACT FROM AUTHOR]

Quantification of spin-charge interconversion has become increasingly important in the fastdeveloping field of spin-orbitronics. Pure spin current generated by spin pumping acts as a sensitive probe for many bulk and interface spin-orbit effects, which has been indispensable for the discovery of many promising new spin-orbit materials. We apply spin pumping and inverse spin Hall effect experiments, as a useful metrology, and study spin-orbit effects in a variety of metals and metal interfaces. We quantify the spin Hall effects in Ir and W using the conventional bilayer structures and discuss the self-induced voltage in a single layer of ferromagnetic permalloy. Finally, we extend our discussions to multilayer structures and quantitatively reveal the spin current flow in two consecutive normal metal layers. [ABSTRACT FROM AUTHOR]

This paper micromagnetically studies the magnetization dynamics driven by the spin-Hall effect in a Platinum/Permalloy bi-layer. For a certain field and current range, the excitation of a uniform mode, characterized by a power with a spatial distribution in the whole ferromagnetic cross section, is observed. We suggest to use the ferromagnet of the bi-layer as basis for the realization of an array of spin-torque oscillators (STOs): the Permalloy ferromagnet will act as shared free layer, whereas the spacers and the polarizers are built on top of it. Following this strategy, the frequency of the uniform mode will be the same for the whole device, creating an intrinsic synchronization. The synchronization of an array of parallely connected STOs will allow to increase the output power, as necessary for technological applications. [ABSTRACT FROM AUTHOR]

Measurement of the magnetic hyperfine fields in metallic thin wires under spin Hall conditions was attempted using the emerging technique, synchrotron-radiation Mössbauer spectroscopy. A Mössbauer probe layer of 57Fe (0.2 nm), 57Fe (0.6 nm), or 119Sn (0.6 nm) was embedded as an electron spin detector near the surfaces of V, Au, Pt, and 56Fe wires. The magnitudes of the magnetic hyperfine fields at the 57Fe and 119Sn nuclear sites that could be enhanced by non-equilibrium conduction- electron spin polarization were measured both without and with the application of an electric current along the wire. Changes in the Mössbauer spectra were not clearly observed, indicating that the magnetic hyperfine field induced by non-equilibrium spin polarization is smaller than the detection limit at least for the measured systems and conditions. [ABSTRACT FROM AUTHOR]

We investigate the influence of a spin current generated from a platinum layer on the ferromagnetic resonance (FMR) properties of an adjacent ferromagnetic layer composed of the halfmetallic half-Heusler material NiMnSb. Spin Hall nano-oscillator devices are fabricated, and the technique of spin torque FMR is used to locally study the magnetic properties as in-plane anisotropies and resonance fields. A change in the FMR linewidth, in accordance with the additional spin torque produced by the spin Hall effect, is present for an applied dc current. For sufficiently large currents, this should yield auto-oscillations, which however are not achievable in the present device geometry. [ABSTRACT FROM AUTHOR]

We present a study of the effective magnetization Meff and the effective damping parameter αeff by means of ferromagnetic resonance spectroscopy on the ferromagnetic (FM) materials Ni81Fe19 (NiFe) and Co40Fe40B20 (CoFeB) in FM/Pt, FM/NM, and FM/NM/Pt systems with the nonmagnetic (NM) materials Ru, Cr, Al, and MgO. Moreover, for NiFe layer systems, the influence of interface effects is studied by way of thickness dependent measurements of Meff and αeff. Additionally, spin pumping in NiFe/NM/Pt is investigated by means of inverse spin Hall effect (ISHE) measurements. We observe a large dependence of Meff and αeff of the NiFe films on the adjacent NM layer. While Cr and Al do not induce a large change in the magnetic properties, Ru, Pt, and MgO affect Meff and αeff in different degrees. In particular, NiFe/Ru and NiFe/Ru/Pt systems show a large perpendicular surface anisotropy and a significant enhancement of the damping. In contrast, the magnetic properties of CoFeB films do not have a large influence of the NM adjacent material and only CoFeB/Pt systems present an enhancement of αeff . However, this enhancement is much more pronounced in NiFe/Pt. By the introduction of the NM spacer material, this enhancement is reduced. Furthermore, a difference in symmetry between NiFe/NM/Pt and NiFe/NM systems in the output voltage signal from the ISHE measurements reveals the presence of spin pumping into the Pt layer in all-metallic NiFe/NM/Pt and NiFe/Pt systems. [ABSTRACT FROM AUTHOR]

We demonstrate the localized excitation and dc electrical detection of magnetostatic surface spin waves (MSSWs) in yttrium iron garnet (YIG) by a shorted coaxial probe. Thin films of NiFe and Pt are patterned at different regions onto a common bulk YIG substrate. A shorted coaxial probe is used to excite spin precession locally near various patterned regions. The dc voltages across the corresponding regions are recorded. For excitation of the Pt regions, the dc voltage spectra are dominated by the spin pumping of MSSWs from YIG, where various modes can be clearly distinguished. For the NiFe region, it is also found that spin pumping from MSSWs generated in YIG dominated the spectra, indicating that the spin pumped currents are dissipated into charge currents via the inverse Spin Hall effect (ISHE) in NiFe. For all regions, dc signals from YIG MSSWs are observed to be much stronger than the ferromagnetic resonance (FMR) uniform mode, likely due to the nature of the microwave excitation. The results indicate the potential of this probe for microwave imaging via dc detection of spin dynamics in continuous and patterned films. [ABSTRACT FROM AUTHOR]

We report on the deformation of microwave absorption spectra and of the inverse spin Hall voltage signals in thin film bilayers of yttrium iron garnet (YIG) and platinum at high microwave power levels in a 9.45-GHz TE011 cavity. As the microwave power increases from 0.15 to 200 mW, the resonance field shifts to higher values, and the initially Lorentzian spectra of the microwave absorption intensity as well as the inverse spin Hall voltage signals become asymmetric. The contributions from opening of the magnetization precession cone and heating of YIG cannot well reproduce the data. Control measurements of inverse spin Hall voltages on thin-film YIG Pt systems with a range of line widths underscore the role of spin-wave excitations in spectral deformation. [ABSTRACT FROM AUTHOR]

We have proposed a method to synchronize multiple spin-transfer torque oscillators based on spin pumping, inverse spin Hall, and spin Hall effects. The proposed oscillator system consists of a series of nano-magnets in junction with a normal metal with high spin-orbit coupling, and an accumulative feedback loop. We conduct simulations to demonstrate the effect of modulated charge currents in the normal metal due to spin pumping from each nano-magnet. We show that the interplay between the spin Hall effect and inverse spin Hall effect results in synchronization of the nano-magnets. [ABSTRACT FROM AUTHOR]

The effect of phase-transition from the quantum-spin-hall to the band-insulator phase on the transport through a three-terminal U-shape spin-separator has been computationally investigated via non-equilibrium green function formalism. Two-dimensional group-IV elements have been comprehensively appraised as the device material. The device separates the unpolarized current injected at the source-terminal into nearly 100% spin-polarized currents of the opposite polarities at the two drain terminals. The phase-transition activated by the electric-field orthogonal to the device is shown to extensively influence the current magnitude and its spin-polarization, and the effect is stronger for materials with smaller intrinsic spin-orbit coupling. Moreover, the device length and the area under field are shown to critically affect the device characteristics on phase change. It is shown that the same device can be operated as a spin-filter by inducing phase-transition selectively in the channel. The results are important for designing spin-devices from Group-IV monolayers. [ABSTRACT FROM AUTHOR]

In semiconductors, the spin degree of freedom is usually disregarded in the theoretical treatment of electron many-body effects such as band-gap renormalization and screening of the Coulomb enhancement factor. Nevertheless, as was observed experimentally in GaAs, not only the singleparticle phase-space filling but also many-body effects are spin sensitive. In this paper, we report on time- and polarization-resolved differential transmission pump-probe measurements in CdTe, which has the same zincblende crystal structure but different material parameters compared to that of GaAs. We show experimentally that at room temperature in CdTe—unlike in GaAs—the pumpinduced decrease of transmission due to the band-gap renormalization can even exceed the transmission increase due to the phase-space filling, which enables to measure directly the spinsensitivity of the band-gap renormalization. We also observed that the influence of the band-gap renormalization is more prominent at low temperatures. [ABSTRACT FROM AUTHOR]

The nucleation of domain walls in ultrathin ferromagnetic/heavy-metal bilayers is studied by means of micromagnetic simulations. In the presence of interfacial Dzyaloshinskii-Moriya interaction, the nucleated walls naturally adopt a homochiral configuration with internal magnetization pointing antiparallely. The interaction between these walls was analyzed and described in terms of a classical dipolar force between the magnetic moments of the walls, which couples their dynamics. Additionally, the current-induced motion of two homochiral walls in the presence of longitudinal fields was also studied by means of a simple one-dimensional model and micromagnetic modeling, considering both one free-defect strip and another one with random edge roughness. It is evidenced that in the presence of pinning due to edge roughness, the in-plane longitudinal field introduces an asymmetry in the current-induced depinning, in agreement with recent experimental results. [ABSTRACT FROM AUTHOR]

The generation of spin current and spin polarization in a two-dimensional electron gas structure is studied in the presence of Dresselhaus and Rashba spin-orbit couplings (SOC), the strength of the latter being modulated in time by an ac gate voltage. By means of the non-Abelian gauge field approach, we established the relation between the Lorentz spin force and the spin current in the SOC system, and showed that the longitudinal component of the spin force induces a transverse spin current. For a constant (time-invariant) Rashba system, we recover the universal spin Hall conductivity of e/8π, derived previously via the Berry phase and semi-classical methods. In the case of a time-dependent SOC system, the spin current is sustained even under strong impurity scattering. We evaluated the ac spin current generated by a time-modulated Rashba SOC in the absence of any dc electric field. The magnitude of the spin current reaches a maximum when the modulation frequency matches the Larmor frequency of the electrons. [ABSTRACT FROM AUTHOR]

Current-induced domain wall motion along high perpendicular magnetocrystalline anisotropy multilayers is studied by means of full micromagnetic simulations and a one-dimensional model in the presence of in-plane fields. We consider domain wall motion driven by the spin Hall effect in the presence of the Dzyaloshinskii-Moriya interaction (DMI). In the case of relatively weak DMI, the wall propagates without significant tilting of the wall plane, and the full micromagnetic results are quantitatively reproduced by a simple rigid one-dimensional model. By contrast, significant wall-plane tilting is observed in the case of strong DMI, and a one-dimensional description including the wall tilting is required to qualitatively describe the micromagnetic results. However, in this strong-DMI case, the one-dimensional model exhibits significant quantitative discrepancies from the full micromagnetic results, in particular, when high longitudinal fields are applied in the direction of the internal domain wall magnetization. It is also shown that, even under thermal fluctuations and edge roughness, the domain wall develops a net tilting angle during its current-induced motion along samples with strong DMI. [ABSTRACT FROM AUTHOR]

Using the nonequilibrium Green's function technique, spin-related Andreev tunneling through a double quantum-dot device attached to a ferromagnetic and a superconducting leads in the presence of the Rashba spin-orbit interaction is explored. We derive the general formulas of spin-related currents, which provide an insight into the Andreev reflection. Our study demonstrates that the spin-polarized Andreev reflection can be achieved, even the pure spin injection may be realized via the spin-orbit coupling and the Zeeman field. The currents show the interesting step-like behaviors and the pronounced rectification effect in the Andreev reflection regime, and the magnitude of currents can be enhanced with increasing the spin polarization of the ferromagnetic electrode. The strong Zemann field and the relative temperature are not favor of the spin-related Andreev transport; moreover, the existence of negative differential conductance of the spin-polarized current under certain conditions is observed and analyzed. These results provide the new ways to manipulate the spin-dependent transport. [ABSTRACT FROM AUTHOR]