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The spin Hall effect (SHE) allows efficient generation of spin polarization or spin current through charge current and plays a crucial role in the development of spintronics. While SHE typically occurs in non-magnetic materials and is time-reversal even, exploring time-reversal-odd (T-odd) SHE, which couples SHE to magnetization in ferromagnetic materials, offers a new charge-spin conversion mechanism with new functionalities. Here, we report the observation of giant T-odd SHE in Fe3GeTe2/MoTe2 van der Waals heterostructure, representing a previously unidentified interfacial magnetic spin Hall effect (interfacial-MSHE). Through rigorous symmetry analysis and theoretical calculations, we attribute the interfacial-MSHE to a symmetry-breaking induced spin current dipole at the vdW interface. Furthermore, we show that this linear effect can be used for implementing multiply-accumulate operations and binary convolutional neural networks with cascaded multi-terminal devices. Our findings uncover an interfacial T-odd charge-spin conversion mechanism with promising potential for energy-efficient in-memory computing. Charge-to-spin conversion allows for the generation and control of spin polarization via a charge current. Typically, this is done with non-magnetic materials with large spin-orbit interactions such as Platinum. Herein, Dai et al demonstrate an intriguing charge-to-spin mechanism, a magnetic spin Hall effect, in a van der Waals heterostructure. [ABSTRACT FROM AUTHOR]

The Fe3GeTe2 monolayer, a ferromagnetic topological candidate with a high Curie temperature of 130 K, has recently garnered considerable interest. We investigated the impact of strain on the electronic, magnetic, and topological properties of the Fe3GeTe2 monolayer using density functional theory calculations. Our results showed that the Fe3GeTe2 monolayer was an itinerant ferromagnet with a high spin polarization of 69.93% and out-of-plane easy magnetization. Tensile strain had no profound impact on the anomalous Hall conductivity (AHC). However, when applying a compressive biaxial strain of −3%, the AHC at the Fermi level was dramatically enhanced to 1.62 e2/h, which is much larger than that of the bulk (0.7 e2/h) and bilayer (1.5 e2/h) material. The large AHC nearly coincided with the singularity of the energy bands near the M point. Our results highlight the potential of using strain engineering to control and optimize the properties of two-dimensional topological materials. [ABSTRACT FROM AUTHOR]

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

Exploration of exotic spin polarizations in single crystals is of increasing interest. A current of longitudinal spins, the so‐called "Dresselhaus‐like" spin current, which is forbidden in materials lacking certain inversion asymmetries, is implied to be generated by a charge current at the interface of single‐crystal CoFe. This work reports unambiguous evidence that there is no indication of spin current of any spin polarizations from the interface or bulk of single‐crystalline CoFe and that the sin2φ second harmonic Hall voltage, which is previously assumed to signify Dresselhaus‐like spin current, is not related to any spin currents but rather a planar Nernst voltage induced by a longitudinal temperature gradient within the sample. Such sin2φ signal is independent of large applied magnetic fields and interfacial spin‐orbit coupling, inversely correlated to the heat capacity of the substrates and overlayers, quadratic in charge current, and appears also in polycrystalline ferromagnets. Strikingly, the planar Nernst effect (PNE) in the CoFe single crystal has a strong fourfold anisotropy and varies with the crystalline orientation. Such strong, anisotropic PNE has widespread impacts on the analyses of a variety of spintronic experiments and opens a new avenue for the development of PNE‐based thermoelectric battery and sensor applications. [ABSTRACT FROM AUTHOR]

We present the observation of field-free spin-orbit-torque (SOT) switching of magnetization in a ferromagnetic semiconductor (Ga,Mn)As film with four-fold in-plane magnetic anisotropy. Magnetization switching is demonstrated between two orthogonal in-plane easy axes through planar Hall resistance measurements as a current is scanned in the absence of a magnetic field. The chirality of the switching of the current hysteresis loop is consistent with SOT arising from spin polarization caused by Dresselhaus- and Rashba-type spin-orbit-induced effective magnetic fields in the (Ga,Mn)As film. The chirality of magnetization switching can be reversed either by changing the direction of the initial magnetization or by applying a constant external magnetic field bias. The SOT magnetization switching between two states was consistently repeated by applying sequential current pluses with alternating polarities, indicating the potential for developing a field-free SOT device. [ABSTRACT FROM AUTHOR]

The robustness of spin–orbit torque (SOT) induced magnetization switching and ease of deposition make type-X devices, where the in-plane easy axis lies perpendicular to the spin polarization, attractive in the field of spintronics. However, universally applicable and straightforward detection of type-X magnetization reversal is still elusive, unlike type-Z switching, which employs DC-based anomalous Hall effect measurement. Here, we demonstrated that the odd planar Hall voltage (O-PHV) signal exhibits an odd symmetry with the application of an external magnetic field which motivates us to develop a reading mechanism for detecting magnetization switching of in-plane magnetized type-X devices. We verified our DC-based reading mechanism in the Pt/Co/NiFe/Pt stack where a thin Co layer is inserted to create dissimilar interfaces about the NiFe layer. Remarkably, the current-induced in-plane fields are found to be significantly large in Pt/Co/NiFe/Pt stack. Furthermore, we employed the O-PHV method to detect the current-induced magnetization switching. The pure DC nature of the writing and reading mechanism of our proposed type-X detection technique through O-PHV makes it the easiest in-plane magnetization detection technique. Moreover, the high repeatability and easy detection of our proposed method will open avenues toward in-plane SOT switching based memory devices and sensors. [ABSTRACT FROM AUTHOR]

Topological quantum materials (TQMs) possess abundant and attractive spin physics, and a Weyl semimetal is the representative material because of the generation of spin polarization that is available for spin devices due to its Weyl nature. Meanwhile, a Weyl semimetal allows the other but unexplored spin polarization due to local symmetry breaking. Here, all‐electric spin device operation using a type‐II Weyl semimetal, WTe2, at room temperature is reported. The polarization of spins propagating in the all‐electric device is perpendicular to the WTe2 plane, which is ascribed to local in‐plane symmetry breaking in WTe2, yielding the spin polarization creation of propagating charged carriers, namely, the spin‐polarized state creation from the nonpolarized state. Systematic control experiments unequivocally negate unexpected artifacts, such as the anomalous Hall effect, the anisotropic magnetoresistance, etc. Creation of all‐electric spin devices made of TQMs and their operation at room temperature can pave a new pathway for novel spin devices made of TQMs resilient to thermal fluctuation. [ABSTRACT FROM AUTHOR]

The generation of perpendicular effective magnetic field or perpendicular spins (σz) is central for the development of energy-efficient, scalable, and external-magnetic-field-free spintronic memory and computing technologies. Here, we report the first identification and the profound impacts of a significant effective perpendicular magnetic field that can arise from asymmetric current spreading within magnetic microstrips and Hall bars. This effective perpendicular magnetic field can exhibit all the three characteristics that have been widely assumed in the literature to "signify" the presence of a flow of σz, i.e., external-magnetic-field-free current switching of uniform perpendicular magnetization, a sin 2φ-dependent contribution in spin-torque ferromagnetic resonance signal of in-plane magnetization (φ is the angle of the external magnetic field with respect to the current), and a φ-independent but field-dependent contribution in the second harmonic Hall voltage of in-plane magnetization. This finding suggests that it is critical to include current spreading effects in the analyses of various spin polarizations and spin–orbit torques in the magnetic heterostructure. Technologically, our results provide a perpendicular effective magnetic field induced by asymmetric current spreading as a novel, universally accessible mechanism for efficient, scalable, and external-magnetic-field-free magnetization switching in memory and computing technologies. [ABSTRACT FROM AUTHOR]

A proximity effect at a van der Waals (vdW) interface enables creation of an emergent quantum electronic ground state. Here we demonstrate that an originally superconducting two-dimensional (2D) NbSe2 forms a ferromagnetic ground state with spontaneous spin polarization at a vdW interface with a 2D ferromagnet V5Se8. We investigated the anomalous Hall effect (AHE) of the NbSe2/V5Se8 magnetic vdW heterostructures, and found that the sign of the AHE was reversed as the number of the V5Se8 layer was thinned down to the monolayer limit. Interestingly, the AHE signal of those samples was enhanced with the in-plane magnetic fields, suggesting an additional contribution to the AHE signal other than magnetization. This unusual behavior is well reproduced by band structure calculations, where the emergence of the Berry curvature along the spin-degenerate nodal lines in 2D NbSe2 by the in-plane magnetization plays a key role, unveiling a unique interplay between magnetism and Zeeman-type spin-orbit interaction in a non-centrosymmetric 2D quantum material. Van der Waals heterostructures made of 2D materials offer a rich platform for the study of novel proximity effects. Here, by means of Hall effect measurements, the authors show a proximity-induced ferromagnetic/ferrovalley ground state with spontaneous spin-valley polarization in a V5Se8/NbSe2 heterostructure. [ABSTRACT FROM AUTHOR]

We study inserting Co layer thickness-dependent spin transport and spinâ€"orbit torques (SOTs) in the Pt/Co/Py trilayers by spin-torque ferromagnetic resonance. The interfacial perpendicular magnetic anisotropy (IPMA) energy density (K s = 2.7 erg/cm2, 1 erg = 10âˆ'7 J), which is dominated by interfacial spinâ€"orbit coupling (ISOC) in the Pt/Co interface, total effective spin-mixing conductance (G eff , tot â†' â†" = 0. 42 Ă— 10 15 Ω âˆ' 1 â‹... m âˆ' 2 ) and two-magnon scattering (β TMS = 0.46 nm2) are first characterized, and the damping-like torque (Îľ DL = 0.103) and field-like torque (Îľ FL = â€"0.017) efficiencies are also calculated quantitatively by varying the thickness of the inserting Co layer. The significant enhancement of Îľ DL and Îľ FL in Pt/Co/Py than Pt/Py bilayer system originates from the interfacial Rashbaâ€"Edelstein effect due to the strong ISOC between Co-3d and Pt-5d orbitals at the Pt/Co interface. Additionally, we find a considerable out-of-plane spin polarization SOT, which is ascribed to the spin anomalous Hall effect and possible spin precession effect due to IPMA-induced perpendicular magnetization at the Pt/Co interface. Our results demonstrate that the ISOC of the Pt/Co interface plays a vital role in spin transport and SOTs-generation. Our finds offer an alternative approach to improve the conventional SOTs efficiencies and generate unconventional SOTs with out-of-plane spin polarization to develop low power Pt-based spintronic via tailoring the Pt/FM interface. [ABSTRACT FROM AUTHOR]

The low temperature anomalous Hall effect in amorphous sputtered SmxCo1−x films is investigated. The microstructure and amorphous nature of the films were characterized by local area diffraction through transmission electron microscopy. The Sm/Co ratio was changed to elucidate the origin of the anomalous Hall effect, which is a proxy for spin polarized transport. The anomalous Hall effect obeys a scaling relation that points to an intrinsic Berry-curvature based mechanism, consistent with recent reports on other amorphous magnetic materials. The anomalous Hall angle increases with increasing Sm content and reaches large values of ∼1%. This observation is related to recent measurements of the local structure in amorphous Sm–Co alloys and suggests that rare earth elements can be utilized to improve electrical control over spin polarization in amorphous magnetic films. [ABSTRACT FROM AUTHOR]

We consider a film of a topological insulator (TI) sandwiched between two ferromagnetic (FM) layers. The system is additionally under an external gate voltage. The surface electron states of TI are magnetized due to the magnetic proximity effect to the ferromagnetic layers. The magnetization of ferromagnetic layers can be changed by applying an external magnetic field or by varying thickness of the topological insulator (owing to the interlayer exchange coupling). The change in the magnetic configuration of the system affects the transport properties of the surface electronic states. Using the Green function formalism, we calculate spin polarization, anomalous Hall effect, and magnetoresistance of the system. We show, among others, that by tuning the gate voltage and magnetizations of the top and bottom FM layers, one can observe the topological transition to the quantum anomalous Hall state. • A topological insulator sandwiched between ferromagnetic layers is considered. • Two magnetization configurations of layers (parallel and antiparallel) are studied. • Switching between trivial and topological insulator state under gate voltage is discussed. [ABSTRACT FROM AUTHOR]

The Møller polarimeter in Hall A at Jefferson Lab in Newport News, VA, has provided reliable measurements of electron beam polarization for the past two decades. Past experiments have typically required polarimetry at the 1% level of absolute uncertainty which the Møller polarimeter has delivered. However, the upcoming proposed experimental program including MOLLER and SoLID have stringent requirements on beam polarimetry precision at the level of 0.4% (The MOLLER Collaboration, 2014; The SoLID collaboration, 2019), requiring a systematic re-examination of all the contributing uncertainties. Møller polarimetry uses the double polarized scattering asymmetry of a polarized electron beam on a target with polarized atomic electrons. The target is a ferromagnetic material magnetized to align the spins in a given direction. In Hall A, the target is a pure iron foil aligned perpendicular to the beam and magnetized out of plane parallel or antiparallel to the beam direction. The acceptance of the detector is engineered to collect scattered electrons close to 90° in the center of mass frame where the analyzing power is a maximum (-7/9). One of the leading systematic errors comes from determination of the target foil polarization. Polarization of a magnetically saturated target foil requires knowledge of both the saturation magnetization and g ′ , the electron g -factor which includes components from both spin and orbital angular momentum from which the spin fraction of magnetization is determined. Target foil polarization has been previously addressed in a 1997 publication "A precise target for Møller polarimetry" by de Bever et al. (1997) at a level of precision sufficient for experiments up to this point. Several shortcomings with the previous published value require revisiting the result prior to MOLLER. This paper utilizes the existing world data to provide a best estimate for target polarization for both nickel and iron foils including uncertainties in magnetization, high-field and temperature dependence, and fractional contribution to magnetization from orbital effects. We determine the foil electron spin polarization at 294 K to be 0.08020 ± 0.00018 (@4 T applied field) for iron and 0.018845 ± 0. 000053 (@2 T applied field) for nickel. We conclude with a brief discussion of additional systematic uncertainties to Møller polarimetry using this technique. • Magnetization of Fe and Ni at room temperature from world data. • Spin fraction of magnetic moment for Fe and Ni from world data. [ABSTRACT FROM AUTHOR]