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Antiferromagnetic skyrmions are tiny particle like spin textures, topologically more stable, having low depinning current density. They are potential candidate for spintronics devices owing to their robustness toward external magnetic field perturbations. Precise control of the skyrmion motion is essential for applications such as racetrack memories, multistate memories, and neuromorphic computing devices. However, in conventional nanotracks, these particles could not be stabilized due to inter-skyrmion repulsion. Hence, in the case of domain wall-based racetracks and multi-state memory devices, extra notches or similar geometric confinements are included within the nanotrack. Here, we show that a stepped nanotrack geometry is one possible solution for controlling the skyrmion dynamics that can be further employed in racetrack memory, multistate memory, and leaky integrate-and-fire neuron devices. Compared to the domain wall depinning current density of ∼1011–1012 A/m2, only ∼106 A/m2 is required for skyrmions. Additionally, we observe that the modified skyrmion racetracks with stepped geometry can mimic the functionality of the biological neuron, including the leaky behavior, eliminating the need for an anisotropy gradient, Dzyaloshinskii–Moriya interaction gradient, or thermal gradient, which is required for the case of domain wall nanotrack. The current density required to drive the skyrmions on this modified nanotrack is ∼1010 A/m2. The effects of defects and edge roughness due to the fabrication process are also studied. [ABSTRACT FROM AUTHOR]

Motivated by the booming development of spintronics based on quantum dot systems, we employed the standard nonequilibrium Green's function theory to derive the transport formula and the heat generation formula of a quantum dot coupled to a substrate and study the relation between spin current and its accompanying heating or cooling. Our results demonstrate that (i) a thermal bias combined with Zeeman splitting can generate steady spin current in a limited dot level range, while a rotating magnetic field can generate time-average spin current in a global range and pure spin current can induce more heat generation than non-pure spin current; (ii) magnetic resonance of spin current can also effectively enhance heat generation; (iii) appropriate environmental temperature in conjunction with a thermal bias makes cooling, while increasing the frequency of the rotating magnetic can easily give rise to the transition from cooling to heating; and (iv) enhancing the coupling between quantum dots and substrates can effectively reduce heat generation while maintaining the fundamental properties of pure spin current. [ABSTRACT FROM AUTHOR]

In this work, we explore the physics and evaluate the merits of strain engineering in two-dimensional van der Waals semiconductor-based FETs (field-effect-transistors) using DFT (density functional theory) to determine the modulation of the channel material properties under strain, and subsequently, their effect on carrier transport properties, i.e., scattering rates, mobility, and then finally simulate and analyze dissipative current transport with a non-equilibrium Green's function–Poisson's equation self-consistent solver. The scattering model includes the effects of charged impurities, intrinsic phonons, and remote phonons as well as the screening effect due to charged carriers. Impact of strain engineering on contact resistance is also incorporated into the transport simulations to determine the potential performance enhancements using strain in practical devices. Based on the comprehensive simulation results, we identify the materials and strain configuration that provide the best improvement in performance. We demonstrate an ON-current gain of 43.3% in a biaxially compressively strained monolayer MoSe2 device achieved through unique valley-crossing. Furthermore, implications of strain engineering for emerging energy-efficient devices based on band-to-band tunneling and spintronics are evaluated to explore uncharted frontiers in beyond-CMOS electron devices. [ABSTRACT FROM AUTHOR]

In the pursuit of advancing neuromorphic computing, our research presents a novel method for generating and precisely controlling intermediate states within heavy metal/ferromagnet systems. These states are engineered through the interplay of a strong in-plane magnetic field and an applied charge current. We provide a method for fine-tuning these states by introducing a small out-of-plane magnetic field, allowing for the modulation of the system's probabilistic response to varying current levels. We also demonstrate the implementation of a spiking neural network (SNN) with a tri-state spike timing-dependent plasticity (STDP) learning rule using our devices. Our research furthers the development of spintronics and informs neural system design. These intermediate states can serve as synaptic weights or neuronal activations, paving the way for multi-level neuromorphic computing architectures. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) demonstrate a broad spectrum of properties encompassing electronic correlations, anisotropic transport, magnetism, and optical behavior. The anisotropy arises from both intrinsic crystal symmetry and extrinsic factors like epitaxial strain and structural asymmetry at TMO interfaces. Weiss and Neel's work has elucidated anisotropic magnetic behavior in antiferromagnetic (AFM) materials. AFM TMOs exhibit unique magnetotransport behavior, including weak antilocalization (WAL) and anisotropic magnetoresistance (AMR). Understanding the magnetic structure and band topology in AFM perovskites and their interfaces enables the tailored design of materials for spintronics and energy conversion. In few interfaces lacking inversion symmetry, Rashba spin–orbit coupling (SOC) induces WAL, a quantum correction in conductivity in a two-dimensional electronic system. Electron accumulation and charge transfer across 3d, 5d transition metal-based perovskite interfaces affect WAL and AMR, as observed in 3d/3d and 3d/5d AFM heterostructures, respectively. Advancements in spintronics rely on exploring spin-dependent transport anisotropy. This review focuses on various scattering mechanisms, categorized as extrinsic and intrinsic, in anisotropic transport, particularly in 3d/5d AFM superlattices. The WAL scattering mechanism depends on both intrinsic factors related to Rashba SOC-induced band topology and extrinsic sources like spin impurities and lattice ions. Moreover, the investigation into AMR mechanisms involves the application of impurity-based extrinsic scattering models, which are aligned with the Rashba and Dresselhauss models on Fermi surfaces. This exploration specifically targets the interface of two-band insulators, exemplified by LaAlO3/SrTiO3 and LaVO3/KTaO3. Furthermore, this model achieves comprehensive coverage, extending its applicability to 3d/5d AFM heterostructures like LaMnO3/SrIrO3 and CaMnO3/CaIrO3. Additionally, the intrinsic scattering mechanism tied to Berry phase effects related to band topology is studied, focusing on the CaMnO3/CaIrO3 superlattice. Despite manipulation challenges stemming from reduced stray fields, AFM materials show potential in interface physics and applications within the realm of spintronics. [ABSTRACT FROM AUTHOR]

The recent discovery of room-temperature ferromagnetism in 2D van der Waals (vdW) materials, such as Fe3GaTe2 (FGaT), has garnered significant interest in offering a robust platform for 2D spintronic applications. Various fundamental operations essential for the realization of 2D spintronics devices are experimentally confirmed using these materials at room temperature, such as current-induced magnetization switching or tunneling magnetoresistance. Nevertheless, the potential applications of magnetic skyrmions in FGaT systems at room temperature remain unexplored. In this work, the current-induced generation of magnetic skyrmions in FGaT flakes employing high-resolution magnetic transmission soft X-ray microscopy is introduced, supported by a feasible mechanism based on thermal effects. Furthermore, direct observation of the current-induced magnetic skyrmion motion at room temperature in FGaT flakes is presented with ultra-low threshold current density. This work highlights the potential of FGaT as a foundation for room-temperature-operating 2D skyrmion device applications.

In our previous work, we synthesized a metal/2D material heterointerface consisting of L 1 0 -ordered iron–palladium (FePd) and graphene (Gr) called FePd(001)/Gr. This system has been explored by both experimental measurements and theoretical calculations. In this study, we focus on a heterojunction composed of FePd and multilayer graphene referred to as FePd(001)/ m -Gr/FePd(001), where m represents the number of graphene layers. We perform first-principles calculations to predict their spin-dependent transport properties. The quantitative calculations of spin-resolved conductance and magnetoresistance (MR) ratio (150 %– 200 %) suggest that the proposed structure can function as a magnetic tunnel junction in spintronics applications. We also find that an increase in m not only reduces conductance but also changes transport properties from the tunneling behavior to the graphite π -band-like behavior. Additionally, we investigate the spin-transfer torque-induced magnetization switching behavior of our junction structures using micromagnetic simulations. Furthermore, we examine the impact of lateral displacements (sliding) at the interface and find that the spin transport properties remain robust despite these changes; this is the advantage of two-dimensional material hetero-interfaces over traditional insulating barrier layers such as MgO. [ABSTRACT FROM AUTHOR]

Magnetic semiconducting materials offer tremendous prospects for spin electronics but is challenging to achieve room-temperature ferromagnetism with unambiguous origin. Herein, a non-stoichiometry strategy is proposed to induce tunable magnetization in MoSe2−x nanoflowers via vacancy-controlled 2H–1T phase transition. The resultant MoSe2−x exhibits robust room-temperature ferromagnetism with significant positive correlation to the content of 1T phase and 2H–1T interfaces. Significant magnetic hysteresis and Curie transition above room temperature have been achieved, confirming the ferromagnetic feature of MoSe2−x. To examine the origin of ferromagnetism, formation energy and spin-polarized calculations have been conducted, indicating that the Se vacancy is beneficial for the formation of the 1T phase and interfacial spin polarization. Localized magnetic moments induced at the 2H–1T interfaces exhibit enhanced magnetism as compared to the net moments from the 1T orbital splitting, giving rise to strong coupling bound magnetic polarons. This work not only advances the understanding on the origin of magnetism in magnetic semiconductors, but also provides an effective route to generate ferromagnetism by defect and/or interface engineering that could be applied to multiferroics, spintronics, and valleytronics. [ABSTRACT FROM AUTHOR]

This Tutorial article focuses on magnetic phenomena and material systems that have gained significant importance since the original development of mumax3, but are challenging to simulate for users who rely solely on the originally provided examples. Alongside the physical background, we provide hands-on examples of advanced magnetic systems, including detailed explanations of complete mumax3 input files (13 in total, often showing different ways to achieve things), and highlighting potential pitfalls where applicable. Specifically, we explore two approaches to incorporate spin–orbit torques in mumax simulations, considering the trade-off between versatility and speed. We also examine complex multilayer material stacks, including synthetic antiferromagnets, demonstrating different implementation methods that again vary in speed, versatility, and realism. A key criterion for selecting the optimal simulation strategy is its suitability for modeling systems where the magnetization varies significantly in the third dimension. The material covered in this Tutorial paper includes content developed for the mumax3 workshop presented during the summer of 2020 within the context of the IEEE online spintronics seminar, along with additional new topics. Throughout the explanations, we ensure broad applicability beyond specific examples. [ABSTRACT FROM AUTHOR]

Chiral materials exhibit many interesting physical properties including circular dichroism, circularly polarized photoluminescence, and spin selectivity. Since its discovery, chirality-induced spin selectivity (CISS) has been demonstrated in many chiral material systems, which indicates promising applications in spintronic devices. Thus, searching for compounds that possess both sizable chirality and excellent spin transport properties is in order. Hybrid organic–inorganic perovskites have attracted intensive research interest due to their long carrier lifetime, high carrier mobility, chemically tunable electronic properties, and long spin lifetime, which make this emerging class of semiconductors promising candidate for spintronics. Moreover, hybrid perovskites integrate inorganic octahedral framework and organic ligands, which may introduce chirality into the materials, especially in quasi-two-dimensional structures. Recently, CISS has been observed in 2D chiral hybrid perovskites, showing the spin filtering effect. Studies of CISS in chiral hybrid perovskites not only help deepen our understanding of CISS mechanism but also shed new light on designing novel spintronic devices. In this review, we summarize the state-of-the-art studies of CISS effect in 2D chiral hybrid organic–inorganic perovskites system. We also discuss the remaining challenges and research opportunities of employing CISS in next-generation spintronic devices. [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]

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

Altermagnets, an emerging class of magnetic materials distinguished by a significant non-relativistic spin splitting band structure but zero net macroscopic magnetization, have recently received considerable attention. Here, we present a theoretical study focusing on the orientation-dependent conductance induced by Andreev reflection (AR) at an altermagnet/altermagnet/superconductor junction. Conventional and equal-spin AR processes occur when the Néel vector directions of the AMs are non-collinear and controllable by the altermagnet's orientation θ and Néel vector direction α. The conductance spectra resemble ferromagnet/ferromagnet/superconductor junctions with parallel or antiparallel magnetization configurations, depending on θ and α. Both the anisotropic altermagnetic state and the equal-spin AR signature can be probed by studying conductance spectra. These findings suggest that altermagnet/superconductor junctions are promising platforms for future superconducting spintronics applications. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions are nanoscale devices that have recently attracted interest in the context of frequency multiplexed spintronic neural networks, due to their interesting dynamical properties, which are defined during the fabrication process, and depend on the material parameters and geometry. This work proposes an approach to extending the functionality of a standard magnetic tunnel junction (MTJ) by introducing an additional ferromagnet/antiferromagnet (FM/AFM) storage layer (SL) vertically integrated with the standard vortex MTJ stack into the nanopillar. The magnetostatic field created by this storage layer acts on the free layer and can be used to change its static and dynamic properties. To tune the magnitude and direction of this magnetostatic field, magnetic reconfiguration is carried out through a thermally assisted switching mechanism using a voltage pulse that heats the AFM layer in the SL above the Néel temperature in the presence of an external field. It is experimentally shown that using an MTJ based on a 600 nm diameter nanopillar with a vortex in the free layer, reconfiguration of the SL allows to continuously change the core precession frequency in the 15 MHz range, or ≈10% of the device frequency. [ABSTRACT FROM AUTHOR]

Single crystals of the d-electron antiferromagnetic metal V5S8 can be prepared by chemical vapour transport with gaseous iodine as a transport agent. We present the outcomes of an endeavour to synthesise high-purity single crystals of V5S8 with reduced crystalline disorder, important to the formation of novel quantum orders. We report results on the residual resistivity ratio of the single crystals as growth parameters are varied including growth temperature, temperature gradient and pre-growth processing of the initial apparatus and reagents. We demonstrate that single crystals of at least a few mm in size can be successfully grown at relatively low temperatures in the range 550–600 °C. The optimisation of this method may imply a better crystallographic organisation, reducing sulphur vacancies and increasing vanadium positional order. The resulting longer electron mean free paths may enhance the probability of finding exotic quantum states of matter at low temperatures. The results presented here may also be of relevance to the development of vanadium sulphide-based energy storage and spintronic devices. [ABSTRACT FROM AUTHOR]

We report on the development of a "two-field-scan" harmonic Hall voltage (HHV) analysis, which collects the second HHV as a function of a swept in-plane magnetic field at 45° and 0° relative to the excitation current, for the determination of the spin-orbit torques of transverse spins in magnetic heterostructures without significant perpendicular spins, longitudinal spins, and longitudinal/perpendicular Oersted fields. We demonstrate that this two-field-scan analysis is as accurate as the well-established but time-consuming angle-scan HHV analysis even in the presence of considerable thermoelectric effects but takes more than a factor of 7 less measurement time. We also show that the fit of the HHV data from a single field scan at 0°, which is commonly employed in the literature, is not reliable because the employment of too many free parameters in the fitting of the very slowly varying HHV signal allows erroneous conclusion about the spin-orbit torque efficiencies. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions are nanoscale spin textures with topological protection properties, which are regarded as promising information carriers. When skyrmions move along nanotracks, their trajectories will shift if affected by skyrmion Hall effect and pinning effect. In this work, the influence of trapezoidal notches in synthetic antiferromagnetic nanotracks on the dynamics of skyrmions is investigated through micromagnetic simulation. The results exhibit that the asymmetric energy barrier induced by the asymmetric geometric structure can hinder reverse motion of skyrmions to realize the unidirectional conduction function of the diodes. Adjusting the height and inclination angle of the trapezoidal notch can effectively expand the current operating windows of the diodes, and the larger the height or inclination angle, the higher the threshold current density to overcome the pinning effect of the geometric energy barrier. Furthermore, the failure mode has a crucial impact on the implementation of skyrmion diodes. By utilizing the asymmetric structure, the forward conduction and reverse cutoff of skyrmion-based diodes can be achieved within 4 ns, with lower energy consumption than traditional diodes, resulting in high efficiency and low energy consumption of diodes. This work proposes a method for realizing the diode functionality by simply altering the geometric structure of the nanotracks, which may play an important role in the design and application of skyrmion-based diodes. [ABSTRACT FROM AUTHOR]

Magnetization dynamics, which determine the speed of magnetization switching and spin information propagation, play a central role in modern spintronics. Gaining its control will satisfy the different needs of various spintronic devices. In this work, we demonstrate that the surface oxidized Cu (CuOX) can be employed for the tunability of magnetization dynamics of ferromagnet/heavy metal (HM) bilayer system. The capping CuOX layer in CoFeB/W/CuOX trilayer reduces the magnetic damping value in comparison with the CoFeB/W bilayer. The magnetic damping even becomes lower than that of the CoFeB/CuOX by ∼ 16% inferring the stabilization of anti-damping phenomena. Further, the reduction in damping is accompanied by a very small reduction in the spin pumping-induced output DC voltage in the CoFeB/W/CuOX trilayer. The simultaneous observation of anti-damping and spin-to-charge current conversion could be attributed to the orbital Rashba effect observed at the HM/CuOX interface. Our experimental findings illustrate that the cost-effective CuOX can be employed as an integral part of modern spintronics devices owing to its rich underneath spin–orbital physics. [ABSTRACT FROM AUTHOR]

Topological spin structures have recently received tremendous attention in condensed matter physics and information science. In addition to the frequently studied skyrmion, skyrmioniums that exhibit a zero topological charge are also promising for spintronics memory carriers. Here, through integrating an interfacial asymmetric Ta/CoFeB/MgO multilayer device with an on-chip conducting wire that induces Oersted fields and Joule heating, we show experimentally the creation and annihilation of magnetic Néel-type skyrmioniums at room temperature, without applying external magnetic fields. In particular, we observe two distinct annihilation dynamics of the skyrmionium by a polar magneto-optical Kerr microscope. Under the direction of Oersted fields that are parallel to the core direction of the skyrmionium, the skyrmionium shrinks inward to form a skyrmion. Under the antiparallel configuration, skyrmionium expands outward to form a stripe domain. By performing micromagnetic simulations, we reveal the Néel-type skyrmionium formation and annihilation dynamics as well as the corresponding energy changes among different magnetic states. Our findings could be important for understanding the formation and annihilation dynamics of skyrmioniums, which also provide an on-chip non-electrical-contact manipulating method of skyrmioniums. [ABSTRACT FROM AUTHOR]

Photopyroelectric‐based circularly polarized light (CPL) detection, coupling the pyro‐phototronic effect and chiroptical phenomena, has provided a promising platform for high‐performance CPL detectors. However, as a novel detection strategy, photopyroelectric‐based CPL detection is currently restricted by the short‐wave optical response, underscoring the urgent need to extend its response range. Herein, visible‐to‐near‐infrared CPL detection induced by the pyro‐phototronic effect is first realized in chiral‐polar perovskites. Specifically, chiral‐polar multilayered perovskites (S‐BPEA)2FAPb2I7 (1‐S, S‐BPEA = (S)‐1‐4‐Bromophenylethylammonium, FA = formamidinium) with spontaneous polarization shows intrinsic pyroelectric and photopyroelectric performance. Strikingly, combining its merits of the pyro‐phototronic effect and intrinsic wide‐spectrum spin‐selective effect, chiral multilayered 1‐S presents efficient photopyroelectric‐based broadband CPL detection performance spanning 405–785 nm. This research first realizes photopyroelectric‐based infrared CPL detection and also sheds light on developing high‐performance broadband CPL detectors based on the pyro‐phototronic effect in the fields of optics, optoelectronics, and spintronics. [ABSTRACT FROM AUTHOR]

Herein, the full potential linearized augmented plane wave (FP‐LAPW) method based on density functional theory has been used to compute the electro‐optical and magnetic characteristics of Mg1−xNixS (x = 0%, 6.25%, 12.5%, and 25%) alloys. The stability of the Mg1−xNixS alloys is verified by the enthalpy of formation energy. In electronic features, the band structure and density of states (DOS) demonstrate the semiconducting behavior in pristine MgS compound, while Mg1−xNixS alloys show half‐metallic ferromagnetic to metallic behavior based on the doping concentration. DOS exhibit a strong pd‐hybridization between Ni‐d and S‐p orbitals in the conduction band). For 6.25%, 12.5%, and 25% concentrations, the calculated total magnetic moment is 1.45364, 1.93086, and 0.71829 μB, respectively which is primarily owing to transition metal d states. Optical characteristics including refraction, absorption, complex dielectric function, and reflectivity are studied in the range of 0–10 eV at various concentrations. The absorption of light is noted from visible to UV spans which increase their significance for optoelectronic usages. Results of Mg1−xNixS alloys reveal their potential applications in optical and magnetic storage devices. [ABSTRACT FROM AUTHOR]

Room temperature and solution‐processible spin‐light emitting diodes (spin‐LEDs) are of practical importance since electronic spins act as information carriers for circularly polarized electroluminescence (CP‐EL) generation. The recent boost of quasi‐2D chiral hybrid perovskites (CHPs) has gained unprecedented attention because of the possible spin manipulation via innate chiral‐induced spin‐orbit coupling (CISOC) without involving cumbersome spin injection from ferromagnets. Herein, a unique method is developed using chiral ionic liquids (CILs) as antisolvents for fabricating highly reproducible and stable lead‐bromide thin films based single junction spin‐LEDs. With this, the chirality is successfully transferred into the perovskites with outstanding chiroptical properties and improved film crystallinities. More than 75% photoluminescent quantum yields (PLQY) and 13% CP‐EL have been achieved. The existence of chiral‐induced spin selectivity (CISS) is proved and a large degree of polarized spin current (Pspin${{{\bm{P}}}_{{{\bf spin}}}}$) of ≈80% with a long spin lifetime exceeding 1.0 ns is attained. Further their magneto‐chiroptical effects are explored through magnetic circular dichroism (MCD) and magneto‐photoluminescence (MPL). The method opens a new avenue for the development of CHPs and high‐performance single junction spin‐LEDs. [ABSTRACT FROM AUTHOR]

In this study, we present results of a comprehensive computational and experimental study of CoFeVAl and CoFeV0.5Mn0.5Al Heusler alloys. It is shown that while CoFeVAl exhibits a fairly large degree of spin polarization, this material is not half-metallic due to the presence of the vanadium spin-down states at the Fermi level. However, replacing 50% of vanadium with manganese results in a nearly half-metallic transition, largely due to the shift of the Fermi level towards occupied states. Moreover, the half-metallicity of CoFeV0.5Mn0.5Al is rather robust in a wide range of considered mechanical strain and under experimentally observed B2-type atomic disorder, thus making this alloy potentially suitable for practical spintronic applications. Both considered alloys exhibit ferromagnetic alignment at larger lattice constants, aside from a relatively small magnetic moment of vanadium which is anti-aligned with the magnetic moments of Co, Fe and Mn. We have synthesized both CoFeVAl and CoFeV0.5Mn0.5Al alloys in cubic structure with some structural disorder using arc melting and annealing. The structural and magnetic properties of the synthesized CoFeV0.5Mn0.5Al alloy are in good agreement with the theoretical calculations but vary slightly from the parent compound. [ABSTRACT FROM AUTHOR]

Spin filtering is a fundamental operation in spintronics, enabling the generation and detection of spin-polarized carriers. Here, we proposed and theoretically demonstrated that a 3d transition metal (TM) doped hydrogenated silicon quantum dot (TM:H-SiQD) is a suitable candidate for spin-filter devices. Using density functional theory, we investigate the structure, electronic properties, and magnetic behavior of TM:H-SiQD. Our calculations demonstrate that Mn:H-SiQD exhibits the highest stability. The designed spin-filter device using Mn:H-SiQD shows a spin-filtering efficiency of 99.9% at 300 K electrode temperature along with very high conductance. This remarkable efficiency positions it as a promising candidate for spintronic devices. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs) are widely applied in spintronic devices for efficient spin detection through the imbalance of spin polarization at the Fermi level. The van der Waals (vdW) property of 2D magnets with atomically flat surfaces and negligible surface roughness greatly facilitates the development of MTJs, primarily in ferromagnets. Here, A‐type antiferromagnetism in 2D vdW single‐crystal (Fe0.8Co0.2)3GaTe2 is reported with TN ≈ 203 K in bulk and ≈ 185 K in 9‐nm nanosheets. The metallic nature and out‐of‐plane magnetic anisotropy make it a suitable candidate for MTJ electrodes. By constructing heterostructures based on (Fe0.8Co0.2)3GaTe2/WSe2/Fe3GaTe2, a large tunneling magnetoresistance (TMR) ratio of 180% at low temperature is obtained, with the TMR signal persisting at near‐room temperature 280 K. Furthermore, the TMR is tunable by the electric field, and the MTJ device operates stably with a low applied bias down to 1 mV (≈0.6 nA), highlighting its potential for energy‐efficient spintronic devices. This work opens up new opportunities for 2D antiferromagnetic spintronics and quantum devices. [ABSTRACT FROM AUTHOR]

The Rashba spin–orbit coupling (RSOC) effect on the polarization and shot noise properties in a strained WSe2 multiple barrier structure is studied by transfer-matrix technique. The results indicate that the spin-dependent Fano factor depends on the strain and RSOC strength with oscillatory evolution. Thus, the value of Fano factor with spin rotation can be tuned mechanically and by an external electric field. Also, Fano factor shows high sensitivity to the number of electrostatic barriers in strained WSe2 multiple barrier structure. Meanwhile, in a strained WSe2 multiple barrier structure both sign and value of the valley and spin polarizations could be adjusted by tuning both RSOC and strain strength. These findings show that a WSe2 multiple barrier structure under strain and RSOC can be useful for future spintronics, straintronic and valleytronic devices. [ABSTRACT FROM AUTHOR]

Chiral 2D and quasi-2D hybrid organic–inorganic perovskites (HOIPs) are emerging as promising materials for a variety of applications principally related to optoelectronics and spintronics, thanks to the combined benefits deriving from both the chiral cation and the perovskite structure. Since its recent birth, this research field is tremendously growing, focalizing on the chemical composition tuning to unveil its influence on the related functional properties as well as on developing devices for practical applications. In this review, we focused on the properties of 2D and quasi-2D chiral HOIPs, firstly providing an overview on their chiroptical behaviour followed by their potential exploitation in devices investigated so far for various applicative fields. [ABSTRACT FROM AUTHOR]

There is a growing interest in mixing spintronics and superconductivity to develop original energy-efficient nonvolatile memory and logic devices. Research works conducted so far have mostly focused on superconductor with critical temperature Tc lower than 10 K. Here, we report on the growth and characterization of MgB2/Ni80Fe20 and MgB2/Co bilayers, where Tc of the MgB2 layer is of the order of 30 K. Ferromagnetic resonance was undertaken to analyze the spin pumping into MgB2. The larger magnetization at saturation in Co, as compared to Ni80Fe20, induces a smaller spin pumping contribution to the damping when MgB2 is normal. A spin pumping reduction was observed for both bilayers when MgB2 becomes superconductor and is attributed to the opening of the superconducting gap. The present results show that MgB2 thin films could be suitable to implement superconducting spintronic at 30 K, which is not only relevant for future technological development but also relaxes experimental constraints related to low-temperature investigations. [ABSTRACT FROM AUTHOR]

The discovery of van der Waals intrinsic magnets has expanded the possibilities of realizing spintronics devices. We investigate the transmission, tunneling magnetoresistance ratio, and spin injection efficiency of bilayer LaI2 using a combination of first-principles calculations and the non-equilibrium Green's function method. Multilayer graphene electrodes are employed to build a magnetic tunnel junction with bilayer LaI2 as ferromagnetic barrier. The magnetic tunnel junction turns out to be a perfect spin filter device with an outstanding tunneling magnetoresistance ratio of 653% under a bias of 0.1 V and a still excellent performance in a wide bias range. In combination with the obtained high spin injection efficiency this opens up great potential from the application point of view. [ABSTRACT FROM AUTHOR]

Computational methods of DFT were utilized to predict the lattices constants, electronic structures, half-metallic character and ferromagnetic properties of Ga1 − xCrxSb compounds at compositions x = 0.25, 0.5, and 0.75. The direct gap of GaSb found with potential TB-mBJ agrees with those calculated with TB-mBJ and HSE06 potentials. Investigations of magnetic and electronic properties using TB-mBJ show that the substituting compounds exhibit integer values of total moments, and they reveal better half-metallic ferromagnetic gaps of 1.269, 1.16, and 1.262 eV respectively for Ga0.75Cr0.25Sb, Ga0.5Cr0.5Sb, and Ga0.25Cr0.75Sb, with spin polarizations of 100%. Therefore, Ga0.75Cr0.25Sb, Ga0.5Cr0.5Sb, and Ga0.25Cr0.75Sb are suitable magnetic compounds for spintronics applications. [ABSTRACT FROM AUTHOR]

The structural, magnetoelectronic, mechanical, thermodynamical, thermoelectric, and optical properties of V2XSb (X = Mn, Fe) alloys are simulated using density functional theory. The structural optimization is done in Hg2CuTi prototype structure with F‐43m space group and confirms its stability in ferromagnetic state. The generalized gradient approximation and modified Becke–Johnson (mBJ) method are used to depict the half‐metallic nature of these alloys. Using Tran Blaha's mBJ potentials, the estimated indirect bandgap along the symmetry points is 0.54 eV for V2MnSb and 0.56 eV for V2FeSb. The total spin magnetic moments of V2XSb (X = Mn, Fe) are 3 and 2 μB which are in accordance with the Slater–Pauling rule. The mechanical stability reveal the ductile nature. The thermodynamic properties are calculated to determine the effect of temperature and pressure. The optical properties of these Heusler alloys are investigated to determine the absorbing power and optical conductivity. Using Boltzmann transport theory, thermoelectric parameters such as Seebeck coefficient and electrical conductivity are also depicted. The designated compound V2XSb (X = Mn, Fe) is unique due to the fact that that it has a high figure of merit (ZT) at both high and low temperatures, which is a beneficial parameter for converting squandered heat energy into beneficial energy that preserves the environment and is free of global warming and other hazardous substances. [ABSTRACT FROM AUTHOR]

Herein, analytical modeling of Fe3O4/x(≈1.1 nm)/Co (x = rubrene, C60, and bathocuproine (BCP)) magnetic tunnel junctions (MTJs) has been performed using rubrene, C60, and BCP as organic spacer layers. The simulation is considered as nonequilibrium Green's function assuming spin precession at ferromagnet/organic semiconductor (FM/OSC) interface defect states. The voltage‐dependent resistances for both parallel (RP) and antiparallel (RAP) orientations have been observed to be dependent on spin injection from FM/OSC defect states. Pinning well‐dependent defect state depths have been associated with band misalignment‐induced lattice distortion at FM/OSC interface of the devices. The large tunnel magnetoresistance (TMR) response for rubrene‐based MTJ device has been attributed to a higher change of FM/OSC defect state depths with voltage. High TMR may have reduced spin torque‐dependent spin precession, leading to lower spin transfer torque for the rubrene device. Hence, engineering of defect states at the FM/OSC interface may lead to the successful realization of enhanced TMR in organic spacer MTJs for high‐performance spintronic memory applications. [ABSTRACT FROM AUTHOR]

This study demonstrates the existence of an evanescent electron wave outside both finite and infinite quantum wells by solving the Dirac equation and ensuring the continuity of the spinor wavefunction at the boundaries. We show that this evanescent wave shares the spin characteristics of the wave confined within the well, as indicated by analytical expressions for the current density across all regions. Our findings suggest that the electron cannot be confined to a mathematical singularity and that quantum information, or quantum entropy, can leak through any quantum confinement. These results emphasize that the electron wave, fully characterized by Lorentz-invariant charge and current densities, should be considered the true and sole entity of the electron. [ABSTRACT FROM AUTHOR]

This paper theoretically examines the impact of integrating 2D transition metal dichalcogenide (TMDCs) materials—MoS2, MoSe2, MoTe2, WS2, and WSe2—with a conventional MgO dielectric to fabricate double-barrier penta-layer (DBPL) magnetic tunnel junction (MTJ) structures. The MTJ device proposed herein is distinguished by a DBPL configuration which incorporates the composite tunnel barrier (CTB) of MgO-MX2-MgO sandwiched between the Fe ferromagnetic electrodes. Using density functional theory (DFT), we conducted a crystallographic analysis on all constituent materials to predict the properties necessary for device operation. Subsequent simulations leveraged an advanced nonequilibrium Green's function-based (NEGF) quantum transport simulator to quantify critical transport phenomena. Notable metrics such as tunneling magnetoresistance (TMR), differential TMR, and spin-transfer torque (STT), both in-plane and out-of-plane, were determined. Additionally, resistance and differential resistance profiles for parallel and antiparallel alignment states were thoroughly evaluated. Our findings elucidate the essential role of CTB composition in determining MTJ performance attributes, with particular dielectric pairings showing a significant enhancement in TMR ratios and an improved resistance differential without compromising the efficiency of STT. Interestingly, our proposed MTJ device shows a substantial increase in TMR values, ranging from 900% to 4300%, with very high sensitivity ranging from 7.33 × 106 T−1 to 3.36 × 107 T−1. [ABSTRACT FROM AUTHOR]

This study aims to enhance the multiferroic properties of bismuth ferrite (BFO) by investigating the effects of substitution with erbium (Er) on the material's structural, optical, and magnetic characteristics. Er-substituted bismuth ferrite (Bi1−xErxFeO3) (x = 0, 0.04, 0.08, 0.12, 0.16) nanoparticles (NPs) were synthesized via the very cost-effective Pechini modified sol–gel method followed by auto-combustion. X-ray diffraction (XRD) patterns confirmed the crystallinity, structure, and purity of the phase, revealing the formation of single-phase materials. The bond structure of the prepared samples was examined using Fourier transform infrared (FTIR) spectroscopy, confirming the significant stretching and bending of bonds of perovskites. Electron paramagnetic resonance (EPR) findings suggested a broadening of the signal as well as a shift of the center of resonance to lower fields. The experimental findings revealed that Er doping has a significant effect on the magnetic ordering and saturation magnetization of BiFeO3. In addition, UV–Vis spectroscopy demonstrated that the energy bandgap in the prepared samples varies from 2.13 eV to 1.71 eV. This research contributes to an understanding of the enhanced structural, magnetic, and optical properties of Er-substituted BFO nanoparticles, which is useful for designing and developing multiferroic materials with enhanced magnetic functionality for next-generation magnetoelectric devices, optoelectronic devices, and photocatalysts. [ABSTRACT FROM AUTHOR]

Rare-earth nitrides are an exciting family of materials with a wide variety of properties desirable for new physics and applications in spintronics and superconducting devices. Among them, samarium nitride is an interesting compound reported to have ferromagnetic behavior coupled with the potential existence of p-wave superconductivity. Synthesis of high-quality thin films is essential in order to manifest these behaviors and understand the impact that vacancies, structural distortions, and doping can have on these properties. In this study, we report the synthesis of samarium nitride monocrystalline thin films on magnesium oxide (001) substrates with a chromium nitride capping layer using molecular beam epitaxy (MBE). We observed a high-quality monocrystalline SmN film with matching orientation to the substrate, then optimized the growth temperature. Despite the initial 2 nm of growth showing formation of a potential samarium oxide layer, the subsequent layers showed high-quality SmN, with semiconducting behavior revealed by an increase in resistivity with decreasing temperature. These promising results highlight the importance of studying diverse heteroepitaxial schemes and open the door for integration of rare-earth nitrides and transition metal nitrides for future spintronic devices. [ABSTRACT FROM AUTHOR]

Optical materials with circularly polarized luminescence (CPL) features have attracted a growing interest due to their crucial role in biological sensing, display, spintronics, information storage, and so forth. However, CPL emissions in hybrid nanoparticle systems, in particular, chirality transfer induced CPL from chiral plasmonic nanoparticles, have rarely been explored due to a lack of effective bottom-up synthesis method. Herein, we creatively take advantage of the newly introduced chiral plasmonic nanoparticles-gold nanohelicoid (GNH) to excite the CPL of achiral Rhodamine 6G (R6G). The fabricated GNH@R6G-SiO2 shows obvious CPL signals with ∣glum∣ up to 0.014. Compared with the single GNH, the photoluminescence (PL) dissymmetry factor of the single GNH@R6G-SiO2 is similar, but with 25 folds higher PL intensities under different circular polarization. Our research not only offers an effective and feasible method to fabricate single-particle level CPL-active materials, but also provides guidelines on how to regulate the CPL of achiral luminophores from chiral plasmonic nanostructures, thereby enlarging the category and quantity of CPL-active materials that can be applied for photonic technologies and visualization biosensing, especially some intracellular chirality related detection. [ABSTRACT FROM AUTHOR]

In the last decades, chemists have developed methods to synthesize helical molecular architectures using a combination of covalent and non‐covalent interactions. Very recently, the new class of completely covalent, one‐handed helical ladder polymers has vigorously emerged. Such polymers can be rationally and programmably obtained through an approach guided by the principles of chirality‐assisted‐synthesis (CAS) and making use synergically of two disciplines that have so far rarely interacted: non‐planar chiral π‐conjugated synthons and ladder polymer chemistry. The precise programmability of the 3D structure and new mechanical and chiroptical properties will lead to potential applications in areas such as enantiorecognition, catalysis, spintronics and chiral‐related optoelectronics. This minireview examines the emerging field of one‐handed helical ladder polymers, analyzing their synthesis, applications, and limitations. [ABSTRACT FROM AUTHOR]

Quantum technologic and spintronic applications require reliable material platforms that enable significant and long‐living spin polarization of excitations, the ability to manipulate it optically in external fields, and the possibility to implement quantum correlations between spins, i.e., entanglement. Here it is demonstrated that these conditions are met in bulk crystals of lead halide perovskites. A giant optical orientation of 85% of excitons, approaching the ultimate limit of unity, in FA0.9Cs0.1PbI2.8Br0.2 crystals is reported. The exciton spin orientation is maintained during the exciton lifetime of 55 ps resulting in high circular polarization of the exciton emission. The optical orientation is robust to detuning of the excitation energy up to 0.3 eV above the exciton resonance and remains larger than 20% up to detunings of 0.9 eV. It evidences pure chiral selection rules and suppressed spin relaxation of electrons and holes, even with large kinetic energies. The exciton and electron–hole recombinations are distinguished by means of the spin dynamics detected via coherent spin quantum beats in magnetic field. Further, electron–hole spin correlations are demonstrated through linear polarization beats after circularly polarized excitation. These findings are supported by atomistic calculations. All‐in‐all, the results establish lead halide perovskite semiconductors as suitable platform for quantum technologies. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) ferromagnetic semiconductors (FM SCs) provide an ideal platform for the development of quantum information technology in nanoscale devices. However, many developed 2D FM materials present a very low Curie temperature (TC), greatly limiting their application in spintronic devices. In this work, we predict two stable 2D transition metal chalcogenides, V3Se3X2 (X = S, Te) monolayers, by using first-principles calculations. Our results show that the V3Se3Te2 monolayer is a robust bipolar magnetic SC with a moderate bandgap of 0.53 eV, while V3Se3S2 is a direct band-gap FM SC with a bandgap of 0.59 eV. Interestingly, the ferromagnetisms of both monolayers are robust due to the V–S/Se/Te–V superexchange interaction, and TCs are about 406 K and 301 K, respectively. Applying biaxial strains, the FM SC to antiferromagnetic (AFM) SC transition is revealed at 5% and 3% of biaxial tensile strain. In addition, their high mechanical, dynamical, and thermal stabilities are further verified by phonon dispersion calculations and ab initio molecular dynamics (AIMD) calculations. Their outstanding attributes render the V3Se3Y2 (Y = S, Te) monolayers promising candidates as 2D FM SCs for a wide range of applications. [ABSTRACT FROM AUTHOR]

Manipulation of the magnetization by spin‐orbit torque (SOT) stands as a crucial advancement in spintronics due to its merits in energy‐efficient and high‐speed operation. However, the conventional SOT devices involving a heavy metal/ferromagnet cannot deterministically switch the perpendicularly magnetized ferromagnet without an external magnetic field, which hinders its practical implementation. Here, room temperature field‐free switching for perpendicularly magnetized ferromagnets is demonstrated using spin currents with the out‐of‐plane spin polarization induced by noncollinear antiferromagnets L12‐Mn3Ir. Both in‐plane and out‐of‐plane spin polarizations are observed, and the tilting angle of the spin polarization is estimated to be ≈10°. The spin Hall conductivity of out‐of‐plane spin is 1.43 × 104 ћ/2e·Ω−1m−1, which is the largest among several 2D and antiferromagnetic materials, including WTe2, RuO2, and Mn3GaN. Furthermore, field‐free SOT switching is demonstrated with an ns‐current pulse, and the current density is comparable with the reported values of the field‐assisted pulse switching. This work paves the way for employing noncollinear antiferromagnets for wafer‐scale spintronic device applications. [ABSTRACT FROM AUTHOR]

In the search for two‐dimensional (2D) magnets operating under ambient conditions, quasi‐2D non‐van der Waals (vdW) materials have attracted considerable research interest over the last five years. In addition to their high Curie temperature (TC), their superior air stability to that of vdW 2D magnets has made them potential candidates for future room‐temperature spintronics applications. Furthermore, recent progress in the thickness‐dependent crystal lattice and magnetic properties of non‐vdW Cr2X3 (X = S, Se, or Te) has brought them to areas that are once set aside for 2D vdW magnets in fundamental research and applications. Despite covalent bonding between magnetic layers, various bottom‐up synthesis methods produced thickness‐controlled flakes of Cr2X3. Moreover, layer‐dependent structural and magnetic properties are among the novel research directions in these materials. This review systematically summarizes recent studies on Cr2X3 crystal structure, their controllable synthesis, and their respective magnetic properties. A summary of some significant results on thickness‐controlled synthesis in Cr2X3 and thickness‐dependent magnetism in Cr2Te3 is presented. Additionally, experimental and theoretical reports are presented to explain interlayer magnetic interaction. The work reveals the interaction between synthesis, structure, and magnetism. Finally, future research directions of new Cr2X3‐based materials, rich magnetism in Cr2X3, and their potential application are discussed. [ABSTRACT FROM AUTHOR]

The big data explosion demands novel data storage technology. Among many different approaches, solitonic racetrack memory devices hold great promise for accommodating nonvolatile and low-power functionalities. As representative topological solitons, magnetic skyrmions are envisioned as potential information carriers for efficient information processing. While their advantages as memory and logic elements have been vastly exploited from theoretical perspectives, the corresponding experimental efforts are rather limited. These challenges, which are key to versatile skyrmionic devices, will be studied in this work. Through patterning concaved surface topography with designed arrays of indentations on standard Si/SiO 2 substrates, we demonstrate that the resultant non-flat energy landscape could lead to the formation of hexagonal and square skyrmion lattices in Ta/CoFeB/MgO multilayers. Based on these films, one-dimensional racetrack devices are subsequently fabricated, in which a long-distance deterministic shifting of skyrmions between neighboring indentations is achieved at room temperature. Through separating the word line and the bit line, a prototype shift register device, which can sequentially generate and precisely shift complex skyrmionic data strings, is presented. The deterministic writing and long-distance shifting of skyrmionic bits can find potential applications in transformative skyrmionic memory, logic as well as the in-memory computing devices. [ABSTRACT FROM AUTHOR]

Spin‐transfer torque (STT) and spin‐orbit torque (SOT) form the core of spintronics, allowing for the control of magnetization through electric currents. While the sign of SOT can be manipulated through material and structural engineering, it is conventionally understood that STT lacks a degree of freedom in its sign. However, this study presents the first demonstration of manipulating the STT sign by engineering heavy metals adjacent to magnetic materials in magnetic heterostructures. Spin torques are quantified through magnetic domain‐wall speed measurements, and subsequently, both STT and SOT are systematically extracted from these measurements. The results unequivocally show that the sign of STT can be either positive or negative, depending on the materials adjacent to the magnetic layers. Specifically, Pd/Co/Pd films exhibit positive STT, while Pt/Co/Pt films manifest negative STT. First‐principle calculations further confirm that the sign reversal of STT originates from the sign reversal of spin polarization of conduction electrons. [ABSTRACT FROM AUTHOR]

Herein we report the existence of room temperature ferromagnetic ordering in pristine cuprous oxide nanocrystals mediated by native point defects present in the material. To demonstrate defect‐induced magnetism, cuprous oxide nanocrystals were synthesized in a simple and sustainable route employing hydroxylamine as the reducing agent. The crystalline phase of the as‐synthesized nanocrystals was investigated and was found to have crystallized in cuprite crystal structure. The optical absorption characteristics exhibits absorption features in the visible region between 400 and 600 nm signifying the presence of optically active defects. The morphology of the sample was examined, which reveals the shape to be corner‐truncated rhombic dodecahedral and the size to be in the range of 200–250 nm. The field‐dependent magnetization measurement at room temperature indicates the presence of collective ferromagnetism with hysteresis behavior (Ms = 210 memu g−1, Mr = 43 memu g−1, Hc = 16.37 mT) due to exchange interaction between the uncompensated spin moments present on the surface of the material. [ABSTRACT FROM AUTHOR]

We present an experimental study of the spin rectification effects produced by ferromagnetic resonance in a NiFe wire. A system of four independent nonmagnetic contact probes was used to supply both rf and dc currents to the wire and to measure dc voltages at different locations in the wire. The rf current drives the ferromagnet's magnetization into resonance and produces a dc photovoltage which results from the rectification of rf current in the ferromagnet with oscillating magnetization. Our 4-probe system provided a means to detect the photovoltage and separate contributions from the ferromagnet/nonmagnet contacts and the bulk of the ferromagnet. The contact photovoltage was found to increase approximately linearly with the dc bias applied to the wire. In contrast, the bulk contribution was found to be almost independent of the dc bias. By tuning properties of individual contact probes we were able to change the magnitude of the contact photovoltage and even reverse its sign. Our results highlight the different contributions to photovoltage and the importance of contact properties/nonlinearities for rectification effects in spintronic devices. [ABSTRACT FROM AUTHOR]

We calculate the dwell time for electron in a magnetic nanostructure with zero average magnetic fields, which is obtained by fabricating three nanosized ferromagnetic stripes on top or bottom of InAs/AlxIn1–xAs. A spin-dependent dwell time is found thanks to the spin–field interaction, which can be used to separate electron-spins in time dimension. Spin-polarised dwell time can be improved by properly patterning ferromagnetic stripes. Such a novel magnetic nanostructure can serve as a temporal spin splitter in the area of semiconductor spintronics. [ABSTRACT FROM AUTHOR]

The terahertz (THz) region of the electromagnetic spectrum, spanning from 0.1 to 10 THz, offers unique opportunities for imaging, spectroscopy, and communication applications. However, the potential of THz technologies has been limited by the availability of efficient and versatile THz emitters. Spintronic THz emitters (STEs), leveraging the ultrafast dynamics of electron spins in magnetic materials, have emerged as a promising solution to this challenge. STEs offer significant advantages, including broad bandwidth, high power output, and room-temperature operation, positioning them at the forefront of THz technology development. Despite these advances, understanding the operational principles and improving the performance of STEs remain areas of active research. This review focuses on the theoretical models that describe the behavior of STEs, aiming to provide a comprehensive overview of the underlying physics and suggest directions for future enhancements. Through a detailed examination of these models, the review seeks to clarify the basics of the physics driving STE performance and highlight innovative strategies for their optimization and application expansion. [ABSTRACT FROM AUTHOR]