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The topological insulator BiSb is promising for spin-orbit torque applications thanks to its high electrical conductivity and giant spin Hall effect. Previous works have reported a large spin Hall angle for BiSb deposited on top of a ferromagnetic layer (FM) with perpendicular magnetic anisotropy. However, since BiSb has large surface roughness, obtaining a large spin Hall angle in BiSb (bottom)/FM is more challenging than in FM/BiSb(top) structures, especially when the FM layer is very thin. Here, we investigate the role of an interfacial layer on the effective spin Hall angle in BiSb (bottom)/FM with in-plane magnetization deposited by magnetron sputtering on sapphire substrates. We showed that inserting an interfacial layer with optimized thickness helps improve the effective spin Hall angle. We achieved a relatively high effective spin Hall angle of 1.7 in BiSb (bottom)/Ru 1 nm/ Co 1 nm/ Pt 1 nm structure.

The spins, which are accumulated at a boundary of a nanomagnet due to the Spin Hall effect, induce a magnetic field, which tilts the nanomagnet magnetization out of its easy axis. Even though this magnetic field is relatively small (about 20 Gauss), it can reverse the magnetization of the nanomagnet if it is modulated in resonance with the magnetization precession and the conditions of the parametric resonance are met. Therefore, such magnetic field can be used to optimize the recording mechanism and to minimize the recording energy for MRAM. A high-precession measurement method of the spin-accumulation-induced magnetic field is developed. The magnetic field is measured in a FeCoB nanomagnet and its properties are studied., 5 pages, 6 figures

The spin Hall magnetoresistance (SMR) of Pt/FeCoB bilayers with in-plane magnetocrystalline anisotropy was analysed with respect to a second order effect in the sensing current which acts, through the spin Hall effect in Pt, as a torque on the magnetization of the ferromagnetic layer and changes slightly its configuration. This leads to a small current dependent shift of the SMR curves in field that allows, in structures with a multidomain state (e.g. Hall bars), the determination of the sign of the magnetic remanence. The SMR measurements were performed as a function of the Pt thickness and the spin Hall angle, the diffusion length and the field-like and damping like SOT efficiency were determined. The results were compared with the values obtained from harmonic Hall voltage and SOT-ferromagnetic resonance (FMR) measurements and show a good agreement.

We have examined a dynamical spin injection in a CoFeB/Pt/CoFeB trilayered structure. Although the contribution of the spin pumping was eliminated by the symmetric spin injection from the upper and lower CoFeB layers, a clear voltage change due to the inverse spin Hall effect has been observed. We find that the observed signal can be quantitatively explained by considering the thermal spin injection due to the heating effect during ferromagnetic resonance (FMR). This innovative demonstration indicates the significant contribution of the FMR heating in the dynamical spin injection.

The development of spintronic devices has been limited by the poor compatibility between semiconductors and ferromagnetic sources of spin. The broken inversion symmetry of some semiconductors may allow for spin–charge interconversion, but its control by electric fields is volatile. This has led to interest in ferroelectric Rashba semiconductors, which combine semiconductivity, large spin–orbit coupling and non-volatility. Here we report room-temperature, non-volatile ferroelectric control of spin-to-charge conversion in epitaxial germanium telluride films. We show that ferroelectric switching by electrical gating is possible in germanium telluride, despite its high carrier density. We also show that spin-to-charge conversion has a similar magnitude to what is observed with platinum, but the charge current sign is controlled by the orientation of ferroelectric polarization. Comparison between theoretical and experimental data suggests that the inverse spin Hall effect plays a major role in switchable conversion. The ferroelectric polarization of epitaxial thin films of germanium telluride can be switched by electrical gating and used to control spin-to-charge conversion.

In this work, we propose and analyze a plasmonic sensor with a three-layer waveguide structure. We consider the transverse spin-dependent shift (SDS) of the horizontal photonic spin Hall effect (PSHE) in the waveguide at a given wavelength (1557 nm) for a TM (transverse magnetic or p-polarized) mode. The sensor structure is analyzed in two ways. First, under the normal methods, that is, angular and intensity interrogation methods, for which the results indicate that the maximum figure of merit (FOM) of 4007.0 RIU−1 is attained for an optimum thickness ( $d_{2}=51$ nm) of the gold layer and this FOM is significantly greater than the corresponding FOM (413.7 RIU−1) reported earlier (for a 50 nm thick gold layer). Also, the average sensitivity increases from 0.0005 to 0.002°/Oe when the volume fraction of Fe3O4 particles ( $c$ ) in the magnetic fluid is increased from 1.48% to 1.93%. Correspondingly, a considerably finer value of the resolution (0.046 Oe) is obtained when the volume fraction is increased to 1.93% (compared to 0.199 Oe at 1.48%). Second way is the proposed method of PSHE, for which the analysis indicates that transverse SDS of the horizontal PSHE is the maximum for $d_{2} = 51$ nm leads to the maximum sensitivity $6.25 \times 10^{7}~\mu$ m/RIU for an amplified angle $\Delta = 0.1^{\circ}$ and $1.09 \times 10^{6}~\mu$ m/RIU for $\Delta = 0.1$ rad in the conventional weak measurements. The corresponding finest possible resolution of magnetic field detection at 1.93% is $1.5 \times 10^{-6}$ Oe in the conventional weak measurements for $\Delta = 0.1^{\circ}$ and $7.8 \times 10^{-8}$ Oe in the modified weak measurements for $\Delta = 0.5$ rad, which are significantly finer than those existing in the related state of the art. The above resolution is also superior to those found under normal methods mentioned earlier. Furthermore, the effect of temperature (24.3 °C–60 °C) on PSHE-based magnetic field sensor’s performance is also analyzed which indicates that the proposed PSHE-based magnetic field sensor should be operated in a thermally controlled milieu.

Computing-in-memory (CiM) architectures have experienced faster growth with the emergence of nanoscale magnetic tunnel junction (MTJ) spintronic devices due to their nonvolatile and CMOS compatible architectures. Recently, spin-transfer torque (STT) and spin Hall effect (SHE)-based several CiM designs have been published. The majority of these designs employ a single-level cell (SLC) memory array and require high write energy to perform logic computations. To mitigate these problems, we propose novel SLC and multilevel cell (MLC) differential spin Hall (DSH) magnetic random access memory (MRAM)-based CiM designs that employed MTJs with field-free switching technique using the in-plane magnetic (IPM) layer. Initially, SLC DSH-MRAM-based magnetic full adder (MFA) is proposed. Furthermore, DSH-MRAM series MLC (sMLC)-based CiM implementations of AND/OR/XOR gates and 1 bit MFA are presented in this work. This DSH-sMLC-based CiM structure exploits a reconfigurable precharge sense amplifier (RPCSA) and innovative MTJ reference mechanism to perform each of the logic operations within a single evaluation cycle and provides complementary logic outputs useful for further computations. The comparative performance analysis of the proposed CiM MFA with SHE-based and voltage-controlled SHE-sMLC-based CiM designs reveals 52% and 33% improvement in write energy, respectively. The proposed design saves 34% area compared to the SHE-based counterpart.

In recent years, the spin Hall effect of light (SHE), also called the photonic spin Hall effect has received extensive research attention, and a series of interesting results have been achieved. This phenomenon has potential applications in nanooptics, quantum information, and optoelectronic devices. In contrast to the pure photon SHE, the photonic spin Hall effect in the surface plasmonic platform exhibits unique properties due to the surface plasmon resonance effect of noble metal material and establishes the connection between photons and electrons. Therefore, the SHE of light in a surface plasmonic platform is expected to be applied to integrated optical devices to create a novel means of developing communication devices. In this paper, we review the progress on the SHE of light based on the plasmonic platform in recent years, and we discuss the future directions of research and prospects for its applications.

The detection of spin current injected from the ferromagnet source to the semiconductor channel is very challenging due to the low injection efficiency at the interface. Especially, it is difficult to detect the spin precession signal in a strong Rashba system without a signal decay. In a semiconductor system, the spin Hall angle is much larger than the spin injection efficiency, so the spin Hall effect is utilized for room temperature operation of the semiconductor-based Rashba devices. To realize spin transport device induce by the spin-charge and charge-spin conversions, the direct spin Hall effect (DSHE) and the inverse spin Hall effect (ISHE) are adopted, respectively. The spin current is clearly detected up to room temperature and the spin transport signal agrees to the temperature dependence of the Rashba effect. From these spin transport signals, we suggest another option to extract Rashba parameters from cryogenic temperature to room temperature. The both signals of DSHE and ISHE also confirm the Onsager Reciprocity in a Rashba system.

The magnetization manipulation by the current-induced spin–orbit torque opens a prospect for energy-efficient spintronic applications. Here, we investigate controllable spin–orbit torques (SOTs) re...

The field of spintronics has attracted tremendous attention recently owing to its ability to offer a solution for the present-day problem of increased power dissipation in electronic circuits while scaling down the technology. Spintronic-based structures utilize electron’s spin degree of freedom, which makes it unique with zero standby leakage, low power consumption, infinite endurance, a good read and write performance, nonvolatile nature, and easy 3D integration capability with the present-day electronic circuits based on CMOS technology. All these advantages have catapulted the aggressive research activities to employ spintronic devices in memory units and also revamped the concept of processing-in-memory architecture for the future. This review article explores the essential milestones in the evolutionary field of spintronics. It includes various physical phenomena such as the giant magnetoresistance effect, tunnel magnetoresistance effect, spin-transfer torque, spin Hall effect, voltage-controlled magnetic anisotropy effect, and current-induced domain wall/skyrmions motion. Further, various spintronic devices such as spin valves, magnetic tunnel junctions, domain wall-based race track memory, all spin logic devices, and recently buzzing skyrmions and hybrid magnetic/silicon-based devices are discussed. A detailed description of various switching mechanisms to write the information in these spintronic devices is also reviewed. An overview of hybrid magnetic /silicon-based devices that have the capability to be used for processing-in-memory (logic-in-memory) architecture in the immediate future is described in the end. In this article, we have attempted to introduce a brief history, current status, and future prospectus of the spintronics field for a novice.

This letter presents a three-bit magnetic analog-to-digital converter (MADC) based on the spin Hall effect, which exploits the spin current flowing at both sides of a heavy metal (HM) layer. The shape of the HM can be adjusted to produce multiple switching thresholds. After the input signal is injected, the magnetization of both free layers in the top and bottom magnetic tunnel junctions (MTJs) can be switched simultaneously. The converted results could be quantified by the states of the corresponding MTJs. In order to improve the accuracy and reliability of quantization, a multilayer structure with a double-check estimation method inspired by or gate operation is designed. This dual-bit MADC can reach up to 667 MHz sampling rate with only 0.17 pJ energy consumption, which is well suited for nonvolatile computing based on magnetic devices.

Magnetostatic surface waves (MSSW) propagation and electromotive force (EMF) generation effects in 14.6 µm-thick yttrium iron garnet (YIG) film covered by 8 nm-thick Pt layer was studied. It was found that MSSW dispersion k = k(f) and transmission S21(f) characteristics in the YIG/Pt structure are very similar to that of the free YIG film. For YIG/Pt structure, we show that EMF (U) demonstrates non-monotonous frequency dependence U(f) and is characterized by two peaks U1,2. The first one (U1) is located near the short-wavelength (k → ∞) cut-off frequency of the MSSW spectrum and can be attributed to MSSW drag of electrons in YIG/Pt structure. The second one (U2) is located near the long-wavelength (k → 0) cut-off frequency of the MSSW spectrum and can be attributed to the inverse spin Hall effect due to the spin pumping.

The concept of gauge fields plays a significant role in many areas of physics from particle physics and cosmology to condensed matter systems, where gauge potentials are a natural consequence of electromagnetic fields acting on charged particles and are of central importance in topological states of matter. Here, we report on the experimental realization of a synthetic non-Abelian gauge field for photons in a honeycomb microcavity lattice. We show that the effective magnetic field associated with TE-TM splitting has the symmetry of Dresselhaus spin-orbit interaction around Dirac points in the dispersion, and can be regarded as an SU(2) gauge field. The symmetry of the field is revealed in the optical spin Hall effect (OSHE), where under resonant excitation of the Dirac points precession of the photon pseudospin around the field direction leads to the formation of two spin domains. Furthermore, we observe that the Dresselhaus field changes its sign in the same Dirac valley on switching from s to p bands in good agreement with the tight binding modelling. Our work demonstrating a non-Abelian gauge field for light on the microscale paves the way towards manipulation of photons via spin on a chip., Original version submitted for peer review

The interactions of photonic spin angular momentum and orbital angular momentum, i.e., the spin-orbit coupling in focused beams, evanescent waves or artificial photonic structures, have attracted intensive investigations for the unusual fundamental phenomena in physics and potential applications in optical and quantum systems. It is of fundamental importance to enhance performance of spin-orbit coupling in optics. Here, we demonstrate a titanium dioxide (TiO2)–based all-dielectric metasurface exhibiting a high efficient control of photonic spin Hall effect (PSHE) in a transmissive configuration. This metasurface can achieve high-efficiency symmetric spin-dependent trajectory propagation due to the spin-dependent Pancharatnam-Berry phase. The as-formed metadevices with high-aspect-ratio TiO2 nanofins are able to realize (86%, measured at 514 nm) and broadband PSHEs in visible regime. Our results provide useful insights on high-efficiency metasurfaces with versatile functionalities in visible regime.

A high degree of tunability and versatility of organic chemistry has paved the way toward molecular engineering of electronic and spintronic devices. Here, we report molecular spin doping of a Pt f...

Topological optics is an emerging research area in which various topological and geometrical ideas are being proposed to design and manipulate the behaviors of photons. Here, the photonic spin Hall effect on the surfaces of topological Weyl semimetal (WSM) films was studied. Our results show that the spin-dependent splitting (i.e. photonic spin Hall shifts) induced by the spin-orbit interaction is little sensitive to the tilt αt of Weyl nodes and the chemical potential μ in type-I WSM film. In contrast, photonic spin Hall shifts in both the in-plane and transverse directions present versatile dependent behaviors on the αt and μ in type-II WSM film. In particular, the largest in-plane and transverse spin Hall shifts appear at the tilts between −2 and −3, which are ~40 and ~10 times of the incident wavelength, respectively. Nevertheless, the largest spin Hall shifts for type-II WSM film with positive αt are only several times of incident wavelength. Moreover, the photonic spin Hall shifts also exhibit different variation trends with decreasing the chemical potential for different signs of αt in type-II WSM films. This dependence of photonic spin Hall shifts on tilt orientation in type-II WSM films has been explained by time-reversal-symmetry-breaking Hall conductivities in WSMs.

Metalens is one kind of two-dimensional ultrathin lenses with subwavelength artificial structures that can focus light in a compact, flexible way. However, most strategies for designing metalenses ...

The topological Hall effect (THE), induced by the Berry curvature that originates from non-zero scalar spin chirality, is an important feature for mesoscopic topological structures, such as skyrmions. However, the THE might also arise from other microscopic non-coplanar spin structures in the lattice. Thus, the origin of the THE inevitably needs to be determined to fully understand skyrmions and find new host materials. Here, we examine the Hall effect in both, bulk- and micron-sized lamellar samples of MnBi. The sample size affects the temperature and field range in which the THE is detectable. Although a bulk sample exhibits the THE only upon exposure to weak fields in the easy-cone state, in micron-sized lamella the THE exists across a wide temperature range and occurs at fields near saturation. Our results show that both the non-coplanar spin structure in the lattice and topologically non-trivial skyrmion bubbles are responsible for the THE, and that the dominant mechanism depends on the sample size. Hence, the magnetic phase diagram for MnBi is size-dependent. Our study provides an example in which the THE is simultaneously induced by two mechanisms, and builds a bridge between mesoscopic and microscopic magnetic structures. © 2022. This work was financially supported by an Advanced Grant from the European Research Council (No. 742068 ) “TOPMAT,” the European Union's Horizon 2020 research and innovation programme (No. 824123 ) “SKYTOP,” the European Union's Horizon 2020 research and innovation programme (No. 766566 ) “ASPIN,” the Deutsche Forschungsgemeinschaft (Project-ID 258499086) “SFB 1143,” the Deutsche Forschungsgemeinschaft (Project-IDs FE 633/30-1, RE 1164/6-1 and LU 2261/2-1) “SPP Skyrmionics,” the DFG through the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter ct.qmat (EXC 2147, Project-ID 39085490). I.S. is grateful to Deutsche Forschungsgemeinschaft for supporting this work through project SO 1623/2-1. D.W. has received funding from the European Research Council (ERC) under the Horizon 2020 research and innovation program of the European Union (grant agreement number 715620 ).

All-optical switching connectors (AOSC) are made of topological insulators (three-dimensional magnetic materials) which reverse the magnetization field using short laser pulses. They gained extensive attention in the past decade due to its high potential for fast and energy-efficient data writing in the spintronic memory applications. Regrettably, using of AOSC in the ferromagnetic multilayers needs multiple pulses for the magnetization reversal that losing its speed and energy efficiency. Here we use the single-pulse mid-infrared and microwave photoexcitation to enable ultrafast manipulation of surface private intraband terahertz and gigahertz transitions in result of spin Hall effect driven motion of magnetic domains in Bi2Se3 synthetic ferromagnetic material of AOSC. This optical excitation is achieved in the magnetic tunnel cell by the optical Hall effect (OHE) of magnetic tunnel junction cells. Therefore, by measuring the (z) axis of optical field of spin Hall effect on the ferromagnetic topological material, the data stored by the optical excitation can be calculated and the write efficiency on the ferromagnetic material is verified. Our experiments show that the use of Bi2Se3 type topological material in both single-pulse AOSC optical excitations is powerful to amplify the OHE field amplitude, which may eventually pave the way for integrated photonic current based memory circuits.

Author(s): Zhou, HA; Liu, J; Wang, Z; Zhang, Q; Xu, T; Dong, Y; Zhao, L; Je, SG; Im, MY; Xu, K; Zhu, J; Jiang, W | Abstract: Interfacially asymmetric magnetic multilayers made of heavy metal/ferromagnet have attracted considerable attention in the spintronics community for accommodating spin-orbit torques (SOTs) and meanwhile for hosting chiral spin textures. In these multilayers, the accompanied interfacial Dzyaloshinskii–Moriya interaction (iDMI) permits the formation of Neel-type spin textures. While significant progresses have been made in Co, CoFeB, Co2FeAl, CoFeGd based multilayers, it would be intriguing to identify new magnetic multilayers that could enable spin-torque controllability and meanwhile host nanoscale skyrmions. In this report, first, thin films made of permanent magnet SmCo5 with perpendicular magnetic anisotropy are synthesized, in which the deterministic SOT switching, enabled by the spin Hall effect, in Pt/SmCo5/Ta trilayer is demonstrated. Further, the stabilization of room-temperature skyrmions with diameters ≈100nnm in [Pt/SmCo5/Ta]15, together with a skyrmionium-like spin texture in [Pt/SmCo5/Ir]15 multilayers is shown. Based on the material specific parameters, micromagnetic simulations are also carried out. The results confirm the presence of chiral spin textures in this new material family. Through interfacial engineering, the results thus demonstrate that rare earth permanent magnets could be a new platform for studying interfacial chiral spintronics.

The photonic spin Hall effect (PSHE) is a promising candidate for controlling the spin states of photons and exploiting next-generation photonic devices based on spinoptics. Herein, the influences of a perpendicular magnetic field on the PSHE appearing on the surface of monolayer black phosphorus (BP) are investigated. Results reveal that both the in-plane and transverse spin-dependent shifts are quantised and show an oscillating pattern due to the splitting of Landau levels (LLs) induced by the external magnetic field B. And the oscillation period of spin Hall shifts gradually increases with strengthening B because of the increase of LL spacings. By contrast, for a fixed magnetic field, as the LL spacings become smaller and smaller with increasing the LL index, the oscillation period of spin Hall shifts gradually decreases as the photonic energy increases. Moreover, it is possibly due to the synergistic role of intrinsic anisotropy, high crystallinity, and quantisation-incurred localised decreases in beating-like complex conductivities of the BP film, giant spin Hall shifts, hundreds of times of the incident wavelength, are obtained in both transverse and in-plane directions. These unambiguously confirm the strong impact of the external magnetic field on the PSHE and shed important insights into understanding the rich magneto-optical transport properties in anisotropic two-dimensional atomic crystals.

Artificial modulation of a neuronal subset through ion channels activation can initiate firing patterns of an entire neural circuit in vivo. As nanovalves in the cell membrane, voltage-gated ion ch...

Spintronics, being a burgeoning area of research, aims to incorporate magnetic tunnel junction (MTJ), as a basic storage building block, to various electronic applications. In continuation of many device structure using MTJ such as spin-transfer torque (STT)-MTJ, spin Hall effect (SHE)-MTJ, spin–orbit torque (SOT)-MTJ, domain wall-based MTJ, and complementary polarizer MTJ, this paper presents a differential spin Hall effect (DSHE). The working and operational analysis of the DSHE-based memory element is presented. It provides 50% improved write energy and more than 1.5 times faster read as compared to a single-ended SHE-MTJ. The device structure is well suited for various differential circuit applications, for example, nonvolatile static random access memory (NVSRAM), nonvolatile flip flop (NVFF), magnetic full adder, and nonvolatile differential sense latch, with a fast and energy-efficient operation. In addition, DSHE-MTJ application for NVSRAM (named as DSNVM) is proposed. Performance of DSNVM is compared with the STT+SHE-based NVSRAM (named as SHENVM). DSNVM shows improved performance in terms of area overhead, restoration delay, and energy. DSNVM provides 40% faster restoration and 16.7% lesser energy as compared to SHENVM. Furthermore, a computational investigation for cell stability is depicted using butterfly curve and N-curve methods. Usually, write noise margins deteriorate in NVSRAMs due to the constituent NV cell. However, read as well as write noise margin is improved in DSNVM.

We report on current-induced ferromagnetic resonance techniques to characterise spin-Hall effect at high temperatures. A microwave current was injected into a patterned CoFeB/Pt bi-layer grown on a glass substrate, simultaneously exerting spin-transfer torques through the spin-Hall effect and also causing Joule heating enabling the control of the device temperature. We measured the device temperature by using the device itself as a local temperature sensor. A clear reduction of CoFeB magnetisation was observed as the device temperature was increased allowing us to estimate the Curie temperature of our CoFeB film to be 920 K. The spin-Hall angle of Pt was quantified as (1.72 ± 0.03) × 10−2 at 300 K and was slightly increased to (1.75 ± 0.02) × 10−2 at 410 K. This simple method can be widely used for quantifying the spin-Hall angle of a large variety of materials at high temperatures.

Stochastic computing (SC) is a promising technology that can be used for low-cost hardware designs. However, SC suffers from its long latency. Although parallel processing can efficiently shorten the latency, duplicated stochastic number generators (SNGs) are necessary, which cause substantial hardware overhead. This paper proposes a scalable SNG based on the spin-Hall-effect (SHE), which is capable of generating multiple independent stochastic streams simultaneously. The design takes advantages of the efficient charge-to-spin conversion from the Spin-Hall material and the intrinsic stochasticity of nanomagnets. Compared to previous spintronic SNGs, the SHE-SNG can reduce the area by $1.6\times -7.8\times $ and the power by $4.9\times -13\times $ while increasing the degree of parallelism from 1 to 16. Compared to CMOS-based SNGs, the proposed SNG obtained $24\times -120\times $ and $53\times $ reduction in terms of area and power, respectively. Finally, three benchmarks were implemented, and the results indicate that SC implementations with the proposed SHE-SNG can achieve $1.2\times -29\times $ reduction of hardware resources compared to implementations with previous CMOS- and spintronic-based designs while scaling the degree of parallelism from 1 to 64.

We first propose the nonlinear spin Hall effect of light (SHEL) and MOSHEL (magneto optic spin Hall effect of light) through a multilayer with graphene and nonlinear substrate (NLS) in terahertz region. The MO transfer matrix method is modified to calculate the SHEL shift in a nonlinear system. The NLS brings bistable characteristics for SHEL in which nonlinear splitting of left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) components can be observed. The Faraday rotation of light in terahertz region causes the asymmetrical SHEL shifts distribution of LHCP and RHCP components. Meanwhile the MO effect of graphene brings modulations for nonlinear SHEL and MOSHEL which provide us new and flexible methods to control spatial light field distribution. In addition, as the delay effect causes the chaos of bistable state system, the SHEL shift can be used as a quantum point for the chaos phenomenon.

We propose a new optical biosensor based on photonic spin Hall effect (PSHE) for detection of DNA hybridization. This device consists of BK7 prism, Ag, SiO2, Au and graphene-MoS2 heterostructure which produces waveguide coupled surface plasmon resonance (WCSPR) effect to enormously enhance PSHE. The adsorption of graphene-MoS2 heterostructure to biomolecules changes the refractive index of the sensing medium, thereby affecting spin-dependent splitting in PSHE. The 2 × 2 transfer matrix method is applied to calculate the generalized Fresnel reflection and we deduce the reflected light shifts in PSHE. We study the correlation between spin-dependent displacements and the refractive index variations of sensed solution to obtain the highest sensitivity in the proposed sensor. However, the PSHE exists in the proposed biosensor is extremely weak, so a signal enhancement technology called weak measurement is adopted to amplify the PSHE shift. Thus, the proposed biosensor can successfully detect the hybridization of probe DNA with target DNA. These results may provide practical applications for PSHE in biological monitoring, medical diagnosis, and food safety.

Surface plasmon polaritons (SPPs) are fundamental collective charge density excitations at surfaces of solid-state plasmas. They can energize physical and chemical processes at the nanoscale, but control of the spatiotemporal evolution of their energy, momentum, and spin is necessary to effectively transfer their quantum properties to molecules and other nanoscopic objects. Thus, to design the coupling of SPPs into other modes of an electronic system, it is important to describe and control their nanofemto spatiotemporal distributions. We investigate the spatial SPP field and spin distributions when launched by illuminating a converging lens coupling structure in an Ag film with obliquely incident linearly or circularly polarized femtosecond light pulses. The propagation and focusing of SPPs are recorded as movies by scanning the pump–probe pulse delay and recording the evolving interference patterns between the SPP and optical fields by ultrafast interferometric time-resolved two-photon photoemission ele...

The method proposed by us in Ref. [1], which eliminates obstacles in the application of electrical methods for studying the spin-Hall effect (SHE) by creating a spin unbalance, which generates a charge unbalance, using the form effect without using polarized injected current, is used in this work to study and compare SHE of different origin - internal (band) and external (structural and impurity). The internal SHE (ISHE) was studied on ultrapure single crystal samples of uncompensated (aluminum) and compensated (tungsten) metals. The influence of external factors on SHE was studied on polycrystalline and impurity aluminum samples. The investigations were carried out in the region of small magnetic fields, which ensure the symmetry of the conventional Hall effect (CHE), which makes it possible to study the chiral behavior of the spin Hall effect.

Measurements of transverse thermoelectric voltage were carried out in Co40Fe60 (CoFe)/Yttrium-Iron-Garnet (YIG) magnetic junctions, using the CoFe film as the spin detector. An unusual dependence of the voltage on the CoFe thickness was observed in the in-plane magnetized (IM) configuration; the junction with a relatively thick CoFe layer (40 nm) exhibits positive signals, whereas the junctions with a thinner CoFe layer (7–10 nm) exhibit negative signals. To find the origin of the behavior, we compare the voltage signals in the CoFe/YIG and CoFe/GGG systems in the IM configuration as well as perpendicularly magnetized (PM) configuration. Furthermore, the anomalous Hall effect was also measured in the Hall-bar shaped CoFe films. The experimental results suggest that the observed thickness dependence of the voltage is attributed to the combination of the inverse spin Hall effect (ISHE) and the anomalous Nernst effect (ANE) in the CoFe layers; the former shows a negative voltage and its contribution gradually increases with decreasing the CoFe thickness, whereas the latter shows a positive and mostly thickness independent voltage. The competition between the ISHE and ANE contributions results in the observed peculiar CoFe-thickness dependence of the transverse thermoelectric voltage.

The unrestricted control of circularly polarized (CP) terahertz (THz) waves is important in science and applications, but conventional THz devices suffer from issues of bulky size and low efficiency. Although Pancharatnam–Berry (PB) metasurfaces have shown strong capabilities to control CP waves, transmission-mode PB devices realized in the THz regime are less efficient, limiting their applications in practice. Here, based on Jones matrix analysis, we design a tri-layer structure (thickness of ~λ/5) and experimentally demonstrate that the structure can serve as a highly efficient transmissive meta-atom (relative efficiency of ~90%) to build PB metadevices for manipulating CP THz waves. Two ultrathin THz metadevices are fabricated and experimentally characterized with a z-scan THz imaging system. The first device can realize a photonic spin Hall effect with an experimentally demonstrated relative efficiency of ~90%, whereas the second device can generate a high-quality background-free CP Bessel beam with measured longitudinal and transverse field patterns that exhibit the nondiffracting characteristics of a Bessel beam. All the experimental results are in excellent agreement with full-wave simulations. Our results pave the way to freely manipulate CP THz beams, laying a solid basis for future applications such as biomolecular control and THz signal transportation., Metasurfaces: efficient terahertz control Ultrathin metasurfaces that can efficiently manipulate circularly polarized terahertz waves in transmission rather reflection have been demonstrated by scientists in China. The devices were fabricated by Min Jia and colleagues from Fudan University and Capital Normal University. The tri-layer structures operate at frequencies of around 0.6 THz and suit future on-chip applications for terahertz photonics. Various designs were tested resulting in a circularly polarized terahertz Bessel beam generator and a device exhibiting the photonic spin Hall effect. The metasurfaces consist of a periodic array of meta-atoms, each composed of three thin layers of metal in a U-shape that are separated and surrounded by polyimide. Changing the angular orientation of the meta-atoms allows different phase gradients to be programmed into the metasurfaces bringing the desired functionality.

Spin-orbit torque (SOT) is an emerging technology that enables the efficient manipulation of spintronic devices. The initial processes of interest in SOTs involved electric fields, spin-orbit coupling, conduction electron spins and magnetization. More recently interest has grown to include a variety of other processes that include phonons, magnons, or heat. Over the past decade, many materials have been explored to achieve a larger SOT efficiency. Recently, holistic design to maximize the performance of SOT devices has extended material research from a nonmagnetic layer to a magnetic layer. The rapid development of SOT has spurred a variety of SOT-based applications. In this Roadmap paper, we first review the theories of SOTs by introducing the various mechanisms thought to generate or control SOTs, such as the spin Hall effect, the Rashba-Edelstein effect, the orbital Hall effect, thermal gradients, magnons, and strain effects. Then, we discuss the materials that enable these effects, including metals, metallic alloys, topological insulators, two-dimensional materials, and complex oxides. We also discuss the important roles in SOT devices of different types of magnetic layers. Afterward, we discuss device applications utilizing SOTs. We discuss and compare three-terminal and two-terminal SOT-magnetoresistive random-access memories (MRAMs); we mention various schemes to eliminate the need for an external field. We provide technological application considerations for SOT-MRAM and give perspectives on SOT-based neuromorphic devices and circuits. In addition to SOT-MRAM, we present SOT-based spintronic terahertz generators, nano-oscillators, and domain wall and skyrmion racetrack memories. This paper aims to achieve a comprehensive review of SOT theory, materials, and applications, guiding future SOT development in both the academic and industrial sectors., an invited paper in the "Advances in Magnetics" series

Quantum oxide materials possess a vast range of properties stemming from the interplay between the lattice, charge, spin and orbital degrees of freedom, in which electron correlations often play an important role. Historically, the spin-orbit coupling was rarely a dominant energy scale in oxides. It however recently came to the forefront, unleashing various exotic phenomena connected with real and reciprocal-space topology that may be harnessed in spintronics. In this article, we review the recent advances in the new field of oxide spin-orbitronics with a special focus on spin-charge interconversion from the direct and inverse spin Hall and Edelstein effects, and on the generation and observation of topological spin textures such as skyrmions. We highlight the control of spin-orbit-driven effects by ferroelectricity and give perspectives for the field., Comment: Submitted to Nature Reviews Materials

High spin to charge conversion efficiency is the requirement for the spintronics devices which is governed by spin pumping and inverse spin Hall effect (ISHE). In last one decade, ISHE and spin pumping are heavily investigated in ferromagnet/ heavy metal (HM) heterostructures. Recently antiferromagnetic (AFM) materials are found to be good replacement of HMs because AFMs exhibit terahertz spin dynamics, high spin-orbit coupling, and absence of stray field. In this context we have performed the ISHE in CoFeB/ IrMn heterostructures. Spin pumping study is carried out for $Co_{40}Fe_{40}B_{20} (12\ nm)/ Cu (3\ nm)/ Ir_{50}Mn_{50} (t\ nm)/ AlO_{x} (3\ nm)$ samples where \textit{t} value varies from 0 to 10 nm. Damping of all the samples are higher than the single layer CoFeB which indicates that spin pumping due to IrMn is the underneath mechanism. Further the spin pumping in the samples are confirmed by angle dependent ISHE measurements. We have also disentangled other spin rectifications effects and found that the spin pumping is dominant in all the samples. From the ISHE analysis the real part of spin mixing conductance (\textit{$g_{r}^{\uparrow \downarrow}$}) is found to be 0.704 $\pm$ 0.003 $\times$ $10^{18}$ $m^{-2}$.

International audience; Terahertz (THz) spin-to-charge conversion has become an increasingly important process for THz pulse generation and as a tool to probe ultrafast spin interactions at magnetic interfaces. However, its relation to traditional, steady state, ferromagnetic resonance techniques is poorly understood. Here we investigate nanometric trilayers of Co/X/Pt (X=Ti, Au or Au0:85W0:15) as a function of the 'X' layer thickness, where THz emission generated by the inverse spin Hall effect is compared to the Gilbert damping of the ferromagnetic resonance. Through the insertion of the 'X' layer we show that the ultrafast spin current injected in the non-magnetic layer defines a direct spin conductance, whereas the Gilbert damping leads to an effective spin mixing-conductance of the trilayer. Importantly, we show that these two parameters are connected to each other and that spinmemory losses can be modeled via an effective Hamiltonian with Rashba fields. This work highlights that magneto-circuits concepts can be successfully extended to ultrafast spintronic devices, as well as enhancing the understanding of spin-to-charge conversion processes through the complementarity between ultrafast THz spectroscopy and steady state techniques.

We generated pulses of electromagnetic radiation with a frequency content up to three terahertz (THz) by optical excitation of Co2Fe0.4Mn0.6Si Heusler alloy/heavy metal bilayers (CFMS/HM) using fs-laser pulses. We attribute the generation process to the conversion of a spin current, generated by the illumination with a fs-laser pulse, to a charge current via the inverse spin Hall effect. We compared the THz emission efficiency in CFMS/Pt and CFMS/Ta bilayers due to their high spin-orbit coupling of Pt and Ta. Surprisingly, our data reveal that CFMS/Pt shows substantially larger THz amplitudes compared to CFMS/Ta. Both bilayers exhibit a tunability of the THz amplitude by external magnetic field both at 300 K and 100 K. Ferromagnetic resonance measurements demonstrate that CFMS/Ta has a high effective spin mixing conductance, describing the efficiency of interfacial spin transport. We observe that the efficiency of the THz radiation cannot be solely described by the spin-orbit coupling strength and the spin diffusion length in the HM material plays an important role.

Strong damping-like spin-orbit torque ({\tau}DL) has great potential for enabling ultrafast energy-efficient magnetic memories, oscillators, and logic. So far, the reported {\tau}DL exerted on a thin-film magnet must result from an externally generated spin current or from an internal non-equilibrium spin polarization in noncentrosymmetric GaMnAs single crystals. Here, we for the first time demonstrate a very strong, unexpected {\tau}DL from current flow within ferromagnetic single layers of chemically disordered, face-centered-cubic CoPt. We establish that the novel {\tau}DL is a bulk effect, with the strength per unit current density increasing monotonically with the CoPt thickness, and is insensitive to the presence or absence of spin sinks at the CoPt surfaces. This {\tau}DL most likely arises from a net transverse spin polarization associated with a strong spin Hall effect (SHE), while there is no detectable long-range asymmetry in the material. These results broaden the scope of spin-orbitronics and provide a novel avenue for developing single-layer-based spin-torque memory, oscillator, and logic technologies., Comment: This manuscript is a primary version, see Advanced Functional Materials for the updated manuscript and for the supporting information

Efficient detection of the magnetic state at nanoscale dimensions is an important step to utilize spin logic devices for computing. Magnetoresistance effects have been hitherto used in magnetic state detection, but they suffer from energetically unfavorable scaling and do not generate an electromotive force that can be used to drive a circuit element for logic device applications. Here, we experimentally show that a favorable miniaturization law is possible via the use of spin-Hall detection of the in-plane magnetic state of a magnet. This scaling law allows us to obtain a giant signal by spin Hall effect in CoFe/Pt nanostructures and quantify an effective spin-to-charge conversion rate for the CoFe/Pt system. The spin-to-charge conversion can be described as a current source with an internal resistance, i.e., it generates an electromotive force that can be used to drive computing circuits. We predict that the spin-orbit detection of magnetic states can reach high efficiency at reduced dimensions, paving the way for scalable spin-orbit logic devices and memories., 13 pages, 3 figures, Extended Data, Supplementary Information

Determining the detailed spin texture of topological surface states is important when one wants to apply topological insulators in spintronic devices. In principle, the in-plane spin component of the surface states can be measured by a method analogous to the so-called Meservey-Tedrow technique. In the present work we suggest that the out-of-plane spin component can be determined by spin Hall effect tunneling spectroscopy. We derive an analytical formula that allows to extract the out-of-plane spin component from spin Hall effect tunneling spectra. We test our formula using realistic tight-binding models of Bi$_2$Se$_3$ and Sb$_2$Te$_3$. We demonstrate that the extracted out-of-plane spin polarization is in very good agreement with the actual out-of-plane spin polarization.

The temperature dependence of the spin pumping process in Fe80Ni20 (Py)/Pt bilayers is analyzed for different Pt capping layer thickness. Samples have been grown by means of dc magnetron sputtering, at room temperature, on top of Si substrates. In order to get an optimized interface between the Py and the Pt layers, the Pt capping layers were deposited In situ. The values of the damping constant, α, obtained for the Py alone samples, around 0.007 at RT, make evident the good quality of the samples. The increase of α due to spin pumping into the Pt layer is clearly appreciated; α values in Py/Pt bilayers are twice the value in Py alone. Spin pumping is confirmed by direct measurements of the inverse spin Hall effect (ISHE) voltage signal (VISHE) measured across the samples. To separate ISHE and spin rectification contributions to VISHE the line shape analysis method has been used and the conditions for its applicability thoroughly discussed. VISHE increases almost linearly on lowering temperature for all the frequencies investigated and smoothly increases as frequency decreases showing roughly a linear dependence with the inverse of the frequency. The Pt layer thickness dependence of α and VISHE suggest a low interfacial spin mixing conductance and high spin memory loss., We acknowledge financial support from the Spanish Ministry of Science, Innovation and Universities through Severo Ochoa Program (SEV-2015-04969), MAT2015-71664-R and RTI2018-099960-B-I00 and funding from the EU (European Union) Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 645658 (DAFNEOX Project) and FEDER Program.

The features of phonon-magnon interconversion in acoustic resonator determine the efficiency of spin pumping from YIG into Pt that may be detected electrically through the inverse spin Hall effect (ISHE). Based on the methods developed in previous works for calculating resonator structures with a piezoelectric (ZnO) and a magnetoelastic layer in contact with the heavy metal (YIG/Pt), we present the results of numerical calculations of YIG film thickness influence on acoustically driven spin waves. We obtain some YIG film thickness regions with various behavior of dc ISHE voltage $U_{ISHE}$. At micron and submicron thicknesses, the higher spin wave resonance (SWR) modes (both even and odd) can be generated with efficiency comparable and even exceeding that of the main mode. The absolute maximum of $U_{ISHE}$ is achieved at the thickness about $s_1 \approx 208$ nm under the excitation of the first SWR.

It is shown that magnetic forces as the force exerted on electron spins at rest, account for both the transverse spin imbalance typical of spin Hall effect and the transverse charge imbalance associated with pure spin currents (inverse spin Hall effect). Considering that for stationary currents the laboratory reference frame, and those for which the spin up and spin down carriers are at rest, are inertial systems one can easily find the forces exerted by the lattice on both spin sub-bands, as well as the force between sub-bands., The authors are indebted to P. Echenique, J. Hirsch, V. Golovach, A. Arnau and J. M. Rojo for many fruitful discussions. This work has been supported by the Spanish Ministry of Innovation, Science and Technology and Spanish Ministry of Economy and Competitiveness through Research Projects MAT2015-67557-C2-1-P, MAT2017-86450-C4-1-R S2013/MIT-2850 NANOFRONTMAG, RTI2018-095856-B-C21, by the European Commission AMPHIBIAN (H2020-NMBP-2016-720853) and by the Comunidad de Madrid S2018/NMT-4321 NANOMAGCOST-CM.

[EN] We analyze the contribution of the inhomogeneous magnetic field induced by an electrical current to the spin Hall effect in metals. The Zeeman coupling between the field and the electron spin leads to a spin dependent force, and to spin accumulation at the edges. We compare the effect of this relativistic correction to the electron dynamics to the features induced by the spin-orbit interaction. The effect of current induced magnetic fields on the spin Hall effect can be comparable to the extrinsic contribution from the spin-orbit interaction, although it does not require the presence of heavy elements with a strong spin-orbit interaction., This work was supported by the Spanish Ministry of Innovation, Science and Technology and Spanish Ministry of Economy and Competitiveness through Research Projects MAT2015-67557-C2-1-P, MAT2017-86450-C4-1-R, S2013/MIT-2850 NANOFRONTMAG and by the European Commission AMPHIBIAN (H2020-NMBP-2016-720853).

Bi-doped Cu alloys are promising materials in the field of Spintronics due to the possibility of having efficient charge to spin conversion via spin Hall effect. To explore this effect, in particular at the nanoscale, it is essential to have a growth method that allows the control of crystal quality, cluster formation and microstructure. In this paper, we demonstrate that electrochemical deposition is a suitable method for the synthesis of these nanomaterials. We report the growth, by template assisted electrodeposition, of high quality, homogeneous nanowires of a diluted alloy of Bi dispersed into a Cu matrix, in which Bi concentration can be easily varied by tuning electrolyte composition. Structural analysis shows that Bi does not cluster but incorporate into the Cu matrix. The short-range order is nevertheless affected by the deposition potential. Cu is basically metallic, and Cu–Cu nearest-neighbor distances are those of bulk Cu, so Bi enters into the Cu structure substitutionally. Using low overpotential, we demonstrate the possibility of growing single crystal nanowires., This work has been partially funded by MAT2017-87072-C4-2-P and RTI2018-097895-B-C43 from the Ministerio de Ciencia e Innovación (MINECO-FEDER). We acknowledge The European Synchrotron (ESRF), MINECO and CSIC for provision of synchrotron radiation facilities, BM25-SpLine staff for the technical support beyond their duties and the financial support for the beamline (PIE-2010-OE-013-200014). We thank the CAI de Difracción de Rayos X, Universidad Complutense de Madrid, for XRD measurements. Electron microscopy observations were carried out at the Centro Nacional de Microscopía Electrónica node of the ICTS-ELECMI. A.S. acknowledges financial support from Comunidad de Madrid for an Atracción de Talento Investigador Contract (2017-t2/IND5395).

We report an investigation of the transport of a pure spin current across a thin layer of organic conductor polyaniline (PANI) sandwiched between a film of the ferrimagnetic insulator yttrium iron garnet (YIG) and a thin layer of platinum. The spin current, generated by spin Seebeck effect of the YIG film, is injected through the YIG/PANI interface, crosses the whole PANI layer and is injected into the Pt layer, where it is converted into a charge current by means of the inverse spin Hall effect and electrically detected as a DC voltage. We also present revealing results of experimental detection of the spin-to-charge current interconversion measured directly on the PANI layer in which we were able obtain the spin Hall angle θ S H = ( 1.70 ± 0.06 ) × 10 - 5 showing that this organic conductor presents a great potential in spintronics devices.

We study spin-dependent direct and Hall conductivities in the threshold region of Fermi energy, ɛ F = 2 J , where J is the exchange integral between the conduction electron spins and the skyrmion spin texture. For ɛ F at the threshold value and above the spin-down electrons are allowed to exist. We find the two in the direct and four narrow peaks in the Hall conductivities for Fermi energies slightly below the threshold value. The found effects are dramatic because the electric current changes by approximately eight times in the narrow range of gate voltages ( ∼ 4 meV). The values of the peaks strongly depend on skyrmion size. For small and very large skyrmion sizes the peak amplitudes are small compared to the conductivity absolute values. At the skyrmion radius a = 6 nm and very light conduction electrons, m ∗ ∼ 1 0 − 2 m e , the extrema are the most pronounced. The temperature evolution reveals the strong smearing effect where the peak-wise behavior completely disappears at room temperatures. Spin transistor could be considered for possible applications where in the narrow region of gate voltage the sharp conductivity change occurs.

Longitudinal spin Seebeck effect (LSSE) refers to generate spin accumulation in ferromagnetic material by thermal gradient, and the spin accumulation can transfer to the attached heavy metal and convert to charge current through inverse spin Hall effect (ISHE). However, the origin of LSSE has been under debate for a long time. In this paper, we prepared the YIG/Pt heterostructure by pulsed laser deposition and magnetron sputter, and studied the relationship between temperature and the voltage of inverse spin Hall effect ( V ISHE ). It is found that the V ISHE vs T curve measured under zero-field (ZFC) and nonzero-field (FC) condition are not coincident with each other, meaning there might exist some spin glass states in the system which may come from the YIG/Pt interface. Moreover, we also compare the experimental data and magnon spin current theory prediction which considers both the bulk magnon spin current effect and the interfacial spin pumping process in the interface. It is found that there is a big deviation between them, meaning that the interface effect may play a crucial role in the temperature-dependent LSSE, especially in low temperature. This work will provide deep insight into the spin transport behavior of the YIG/Pt heterostructure.