Zhong Shi

Spin-orbit torque efficiency is conventionally fixed by bulk materials. D-wave altermagnets introduce an additional nonrelativistic spin-charge conversion channel beyond the inverse spin-Hall effect. Using prototypical candidate RuO_{2} as an example, we show that the adjacent ferromagnet alone can dictate both the magnitude and sign of spin-charge conversion. Spin-pumping measurements on RuO_{2}/Y_{3}Fe_{5}O_{12} (YIG) and RuO_{2}/Ni_{80}Fe_{20} (Py) bilayers yield opposite effective spin-Hall angles that persist across crystalline and polycrystalline RuO_{2}. Inserting an ultrathin Au spacer at the RuO_{2}/YIG interface reverses the signal, evidencing a dominant interfacial inverse Rashba-Edelstein effect, whereas RuO_{2}/Py is governed by the bulk inverse spin-Hall effect. First-principles calculations trace this dichotomy to interface-selective band hybridization: Rashba surface states survive at the insulating YIG contact yet are quenched by metallic Py. Our findings establish ferromagnetic interfacing as a deterministic knob for tailoring spin-charge conversion in altermagnetic oxides, paving the way to field-free, low-dissipation spintronic memory devices.

Spin-orbit torque (SOT) enables efficient magnetic moment control through current-induced torques, playing a critical role in spin chirality switching for non-collinear antiferromagnetic (AFM) materials. However, achieving stable chirality switching remains challenging, with the roles of the two SOT components field-like torque (FLT) and damping-like torque (DLT) remaining unclear. Here, we demonstrate deterministic 180°chirality switching in monolayer Mn₃Sn by introducing Néel spin currents perpendicular to the initial atomic magnetic moments to break the symmetry. In particular, by increasing the FLT component, the critical switching current density and the switching time can be effectively reduced. We also provide diagrams of the switching process of sublattices with different coefficients of FLT and DLT. Our research results contribute to a further understanding of the switching mechanism of AFM materials and the development of an ultrafast AFM-based magnetic random access memory (MRAM).

The spin Hall efficiency (ξ) is a crucial parameter that evaluates the charge‐to‐spin conversion capability of a material, and thus materials with higher ξ are highly desirable in spin–orbit torque (SOT) devices. Recent studies have highlighted the use of ferromagnetic materials as robust spin sources, paving the way for the development of more efficient SOT devices. To accelerate this innovation, it is essential to pursue ferromagnetic materials of high ξ. Here the experimental observation of a large spin Hall efficiency is reported in ferromagnetic Heusler alloy Co₂MnAl (CMA)‐based magnetic trilayers. Utilizing the current‐induced hysteresis loop shift technique, the spin Hall efficiency is determined to be 0.077 for the B2‐phase and 0.029 for the disordered CMA. Notably, magnetization switching both with and without the application of an external auxiliary magnetic field were achieved in these trilayers. The enhancement of ξ is attributed to the formation of chemical ordering in CMA. These findings provide new avenues for the development of ferromagnet‐based SOT devices.

The 2D magnet Fe3GaTe2 has received considerable attention for its high Curie temperature (TC), robust intrinsic ferromagnetism, and significant perpendicular magnetic anisotropy (PMA). In this study, the dynamic magnetic properties of Fe3GaTe2 are systematically investigated using an all-optical pump–probe technique. We find that the spin precession frequency (f) is as high as 351.2 GHz at T = 10 K under a field of H = 70 kOe. However, it decreases to 242.8 GHz at 300 K, mainly due to the reduced effective PMA field (Hkeff). The Gilbert damping factor (α) is modest, which increases from 0.039 (10 K) to 0.075 (300 K) owing to the enhanced scattering rate. Interestingly, when Fe3GaTe2 is coupled with 2 nm of Co, the Hkeff, f, and α just decrease slightly, highlighting the dominant influence of Fe3GaTe2. These findings substantially deepen our understanding of Fe3GaTe2, promoting the development of spintronic devices based on advanced 2D magnetic materials.

High-quality rare-earth iron garnet (ReIG) Tb$_3$Fe$_5$O$_{12}$ (TbIG) thin films are epitaxially grown on a series of (111)-oriented garnet substrates with various lattice constants. The coherent growth induces a substrate-dependent in-plane tensile or compressive strain in the TbIG film. Measurements of the anomalous Hall-like effect (AHLE) in TbIG/Pt heterostructures show that the compensation temperature of TbIG films monotonically changes with the film strain. The strain results in a variation of the distances between magnetic atoms in the TbIG crystal and therefore the corresponding exchange interactions. The latter is explicitly calculated as a function of the lattice strain based on density functional theory, reproducing the observed experimental results. This work provides a versatile way to optimize ReIG-based spin-orbit torque devices.

The fundamental mechanisms of ultrafast demagnetization and magnetization recovery processes in ferromagnetic materials remain incompletely understood. The investigation of different dynamic features which depend on various physical quantities requires a more systematic approach. Here, the femtosecond laser-induced demagnetization and recovery dynamics in L1₀-Fe_0.5Pt_0.5 alloy film are studied by utilizing time-resolved magneto-optical Kerr measurements, focusing on their dependences of excitation fluence and ambient temperature over broad ranges. Ultrafast demagnetization dominated by Elliott-Yafet spin-flip scattering, and two-step magnetization recovery processes are found to be involved in all observations. The fast recovery time corresponding to spin–lattice relaxation is much shorter than that of many ferromagnets and increase with excitation fluence. These can be ascribed to the strong spin–orbit coupling (SOC) demonstrated in FePt and the reduction of transient magnetic anisotropy, respectively. Surprisingly, the demagnetization time exhibits no discernible correlation with ambient temperature. Two competitive factors are proposed to account for this phenomenon. On the other hand, the spin–lattice relaxation accelerates as temperature decreases due to enhanced SOC at lower ambient temperature. A semiquantitative analysis is given to get a visualized understanding. These results offer a comprehensive understanding of the dynamic characteristics of ultrafast demagnetization and recovery processes in iron-based materials with strong SOC, highlighting the potential for regulating the magnetization recovery process through temperature and laser fluence adjustments.