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Electrical generation and transduction of polarized electron spins in semiconductors (SCs) are of central interest in spintronics and quantum information science. While spin generation in SCs is frequently realized via electrical injection from a ferromagnet (FM), there are significant advantages in nonmagnetic pathways of creating spin polarization. One such pathway exploits the interplay of electron spin with chirality in electronic structures or real space. Here, utilizing chirality-induced spin selectivity (CISS), the efficient creation of spin accumulation in n-doped GaAs via electric current injection from a normal metal (Au) electrode through a self-assembled monolayer (SAM) of chiral molecules (α-helix l-polyalanine, AHPA-L), is demonstrated. The resulting spin polarization is detected as a Hanle effect in the n-GaAs, which is found to obey a distinct universal scaling with temperature and bias current consistent with chirality-induced spin accumulation. The experiment constitutes a definitive observation of CISS in a fully nonmagnetic device structure and demonstration of its ability to generate spin accumulation in a conventional SC. The results thus place key constraints on the physical mechanism of CISS and present a new scheme for magnet-free SC spintronics.

Recently, topological insulators (TIs) have regained extensive attention in spintronics due to their potential applications in new‐generation spintronic devices, following the discovery of the quantum Hall effect and quantum anomalous Hall effect, which introduce the topological concept. In this review, the exotic spin transport phenomena are explored in TIs. The review offers a concise overview of the fundamental principles of TIs, followed by an exploration of diverse fabrication methods for TI materials. Characterization techniques of the topological surface states are also presented. The review delves into the intriguing spin current transport phenomena, focusing on spin‐to‐charge and charge‐to‐spin conversions in TI/ferromagnet bilayers, respectively. The review culminates summarizing key insights and project future directions for research on spin transport phenomena in TIs, emphasizing practical implications. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions (MTJs) based on novel states of two-dimensional (2D) magnetic materials will significantly improve the value of the tunneling magnetoresistance (TMR) ratio. However, most 2D magnetic materials exhibit low critical temperatures, limiting their functionality to lower temperatures rather than room temperature. Moreover, most MTJs experience the decay of TMR ratio at large bias voltages within a low spin injection efficiency (SIE). Here, we construct a series of MTJs with Weyl half-semimetal (WHSM, e.g. MnSiS _3 , MnSiSe _3 , and MnGeSe _3 monolayers) as the electrodes and investigate the spin-dependent transport properties in these kind of lateral heterojunctions by employing density functional theory combined with non-equilibrium Green’s function method. We find that an ultrahigh TMR (∼10 ^9 %) can be obtained firmly at a small bias voltage and maintains a high SIE even at a large bias voltage, and MnSiSe _3 monolayer is predicted to exhibit a high critical temperature. Additionally, we reveal that the same structure allows for the generation of fully spin-polarized photocurrent, irrespective of the polarization angle. These findings underscore the potential of WHSMs as candidate materials for high-performance spintronic devices.

FeRh has been demonstrated to be an important material for the observation of magnetic phase transitions, such as the first-order transition from an antiferromagnetic (AFM) to a ferromagnetic (FM) state, in response to changes in the temperature. This is because of the magnetic moment induced in Rh atoms above the magnetic phase transition temperature. In the present study, we focus on the longitudinal spin Seebeck effect (LSSE), which involves the generation of spin voltage as a result of a temperature gradient in FM materials or FM insulators, and experimentally assess the effect of the crystalline quality of FeRh films and the properties of the substrate on the LSSE thermopower during the FM-AFM phase transition. The measured LSSE thermopower of an epitaxial (110)-oriented FeRh film grown on an Al 2 O 3 substrate is approximately 60 times higher than that of a polycrystalline FeRh film on a SiO 2 /Si substrate. This can be explained by the high magnetic sensitivity and superior FM properties of (110)-oriented epitaxial FeRh films. Furthermore, by comparing the transverse thermoelectric voltage for in-plane magnetized (IM) and perpendicularly magnetized (PM) configurations, we quantitively evaluate the contribution of the exclusive anomalous Nernst effect (ANE) to the LSSE signals in the FeRh/Al 2 O 3 structure, finding it to be approximately 15-30% over a temperature range of 75-300 K. LSSE measurements in Pt/FeRh films are thus demonstrated to provide a versatile pathway for the development of thermoelectric power generation applications and other practical spintronics and neuromorphic computing devices.

Constructing nanoscale spin devices has been a crucial pursuit in the field of nano spintronics. Here, by using the density functional theory (DFT) and nonequilibrium Green's function (NEGF) method, high-performance nanoscale spin-MOSFET devices using half-metallic 2D Cr 2 Se 3 as electrodes are theoretically designed. Specifically, seven typical two-dimensional (2D) semiconductors, Sb, Bi, BP, BAs, MoTe 2 , WTe 2 , and WSeTe (with two different contacting surfaces), are considered here as the channel materials. The properties of contact interfaces between these 2D semiconductors and half-metallic 2D Cr 2 Se 3 are first investigated. It is found that except BP and BAs (having Schottky contacts with Cr 2 Se 3 ), the other 2D semiconductors have vertical Ohmic contacts with Cr 2 Se 3 among which Cr 2 Se 3 /Sb, Cr 2 Se 3 /MoTe 2 , Cr 2 Se 3 /WTe 2 , Cr 2 Se 3 /WSeTe-Se, and Cr 2 Se 3 /WSeTe-Te retain the half-metallic characteristic. Then, these 2D semiconductors with Ohmic vertical contacts are further used to construct spin-MOSFET devices. The results show that devices constructed by half-metallic vertical contacting systems have nearly 100% SIE and therefore giant MR (>10 7 %) when the gate voltage varies. Furthermore, four designed spin-MOSFET devices, namely, Cr 2 Se 3 /MoTe 2 , Cr 2 Se 3 /WTe 2 , Cr 2 Se 3 /WSeTe-Se, and Cr 2 Se 3 /WSeTe-Te spin-MOSFET have high efficient gate modulations on the magnitude of completely spin-polarized source-drain current with Cr 2 Se 3 /WTe 2 having the smallest SS value of 134.1 mV/dec. The calculations suggest that Cr 2 Se 3 is a good candidate for constructing spin-MOSFET devices. Our study sheds light on the design of high-performance nanoscale spin-MOSFET devices by using two-dimensional half-metallic electrodes.

Electrical generation and transduction of polarized electron spins in semiconductors (SCs) are of central interest in spintronics and quantum information science. While spin generation in SCs is frequently realized via electrical injection from a ferromagnet (FM), there are significant advantages in nonmagnetic pathways of creating spin polarization. One such pathway exploits the interplay of electron spin with chirality in electronic structures or real space. Here, utilizing chirality-induced spin selectivity (CISS), the efficient creation of spin accumulation in n-doped GaAs via electric current injection from a normal metal (Au) electrode through a self-assembled monolayer (SAM) of chiral molecules (α-helix l-polyalanine, AHPA-L), is demonstrated. The resulting spin polarization is detected as a Hanle effect in the n-GaAs, which is found to obey a distinct universal scaling with temperature and bias current consistent with chirality-induced spin accumulation. The experiment constitutes a definitive observation of CISS in a fully nonmagnetic device structure and demonstration of its ability to generate spin accumulation in a conventional SC. The results thus place key constraints on the physical mechanism of CISS and present a new scheme for magnet-free SC spintronics., (© 2024 Wiley‐VCH GmbH.)

We examine the coherent spin-dependent transport properties of the van der Waals (vdW) ferromagnet Fe 4 GeTe 2 using density functional theory combined with the nonequilibrium Green's function method. Our findings reveal that the conductance perpendicular to the layers is half-metallic, meaning that it is almost entirely spin-polarized. This property persists from the bulk to a single layer, even under significant bias voltages and with spin-orbit coupling. Additionally, using dynamical mean field theory for quantum transport, we demonstrate that electron correlations are important for magnetic properties but minimally impact the conductance, preserving almost perfect spin-polarization. Motivated by these results, we then study the tunnel magnetoresistance (TMR) in a magnetic tunnel junction consisting of two Fe 4 GeTe 2 layers with the vdW gap acting as an insulating barrier. We predict a TMR ratio of ∼500%, which can be further enhanced by increasing the number of Fe 4 GeTe 2 layers in the junction.

While the recent prediction and observation of magnetic skyrmions bears inspiring promise for next-generation spintronic devices, how to detect and track their position becomes an important issue. In this work, we investigate the spin transport in a two-dimensional magnetic nanoribbon with the Hall-bar geometry in the presence of Rashba spin-orbit coupling and magnetic skyrmions. We employ the Kwant tight-binding code to compute the Hall conductance and local spin-polarized current density. We consider two versions of the model: One with single skyrmion and one with two separate skyrmions. It is found that the size and position of the skyrmions strongly modulate the Hall conductance near the Hall-bar position. The geometry of the Hall bar also has a strong influence on the Hall conductance of the system. With the decreasing of the width of Hall leads, the peak of Hall conductance becomes sharper. We also show the spatial distribution of the spin-polarized current density around a skyrmion located at different positions. We extend this study toward two separate skyrmions, where the Hall conductance also reveals a sizable dependence on the position of the skyrmions and their distance. Our numerical analysis offers the possibility of electrically detecting the skyrmion position, which could have potential applications in ultrahigh-density storage design., (© 2024 IOP Publishing Ltd.)

Molecular semiconductor (MSC) is a promising candidate for spintronic applications benefiting from its long spin lifetime caused by light elemental-composition essence and thus weak spin-orbit coupling (SOC). According to current knowledge, the SOC effect, normally dominated by the elemental composition, is the main spin-relaxation causation in MSCs, and thus the molecular structure-induced SOC change is one of the most concerned issues. In theoretical study, molecular isomerism, a most prototype phenomenon, has long been considered to possess little difference on spin transport previously, since elemental compositions of isomers are totally the same. However, here in this study, quite different spin-transport performances are demonstrated in ITIC and its structural isomers BDTIC experimentally, for the first time, though the charge transport and molecular stacking of the two films are very similar. By further experiments of electron-paramagnetic resonance and density-functional-theory calculations, it is revealed that noncovalent-conformational locks (NCLs) formed in BDTIC can lead to enhancement of SOC and thus decrease the spin lifetime. Hence, this study suggests the influences from the structural-isomeric effect must be considered for developing highly efficient spin-transport MSCs, which also provides a reliable theoretical basis for solving the great challenge of quantificational measurement of NCLs in films in the future., (© 2024 Wiley‐VCH GmbH.)

In this paper, we analyze the influence of topological magnon phases on quantum correlation and spin transport on layered ferrimagnets which is a fascinating topic in condensed matter physics. In the study of topological phases manipulated by an external magnetic field in layered ferrimagnets for the field applied along the easy axis, the system can transfer between a nodal-loop semimetal phase and a Weyl semimetal phase in perpendicularly and laterally magnetized geometries, respectively. The anisotropic nature of these materials means that the interactions between spins depend on their relative orientations in different directions. We analyze the effect of topological magnon bands induced by the coupling parameters on quantum correlation. The influence of these coupling parameters is also investigated on spin conductivity longitudinal and transversal as well. • The ground state properties are discussed. • Entanglement negativity as a function of the coupling parameters is analyzed. • Transport coefficients are calculated, [ABSTRACT FROM AUTHOR]

Significant attention has been drawn to electronic transport in chiral materials coupled to ferromagnets in the chirality-induced spin selectivity (CISS) effect. A large magnetoresistance (MR) is usually observed, which is widely interpreted to originate from spin (dependent) transport. However, there are severe discrepancies between the experimental results and the theoretical interpretations, most notably the apparent failure of the Onsager reciprocity relations in the linear response regime. We provide an alternative mechanism for the two terminal MR in chiral systems coupled to a ferromagnet. For this, we point out that it was observed experimentally that the electrostatic contact potential of chiral materials on a ferromagnet depends on the magnetization direction and chirality. The mechanism that we provide causes the transport barrier to be modified by the magnetization direction, already in equilibrium, in the absence of a bias current. This strongly alters the charge transport through and over the barrier, not requiring spin transport. This provides a mechanism that allows the linear response resistance to be sensitive to the magnetization direction and also explains the failure of the Onsager reciprocity relations. We propose experimental configurations to confirm our alternative mechanism for MR.