High temperature studies of spin Hall effect have often been neglected despite its profound significance in real-world devices. In this work, high temperature spin torque ferromagnetic resonance measurement was performed to evaluate the effects of temperature on the Gilbert damping and spin Hall efficiency of Pt x cu 1−x. When the temperature was varied from 300 K to 407 K, the Gilbert damping was relatively stable with a change of 4% at composition x = 66%. Alloying Pt and Cu improved the spin Hall efficiency of Pt 75 cu 25 /Co/Ta by 29% to a value of 0.31 ± 0.03 at 407 K. However, the critical switching current density is dependent on the ratio between the Gilbert damping and spin Hall efficiency and the smallest value was observed when x = 47%. It was found that at this concentration, the spin transparency was at its highest at 0.85 ± 0.09 hence indicating the importance of interfacial transparency for energy efficient devices at elevated temperature.

We report the giant spin current generation in CuTb alloys arising from the spin Hall effect. The maximum spin Hall angle from our CuTb-based magnetic heterostructures was found to be −0.35 ± 0.02 for Cu0.39Tb0.61. We find that the contribution of skew scattering is larger than the side jump for lower Tb concentrations (<14.9%), while the converse is true for higher Tb concentrations. Additionally, we also studied the Gilbert damping parameter, spin diffusion length, and spin-mixing conductance. Interfacial spin transparency was found to be 0.55 ± 0.03 for the CoFeB/Cu0.53Tb0.47 interface. The spin diffusion length and spin-mixing conductance of the Cu0.53Tb0.47 alloy are λsd = 2.5 ± 0.3 nm and G ↓↑ = (24.2 ± 1.0) × 1015 cm–2, respectively. Our results pave a way for rare-earth metals to be used as a spin Hall material in highly efficient SOT devices.

A comprehensive understanding of numerous electrical current-induced magnetic texture transformations is necessary to ensure the reliability of skyrmionic devices during operation. Here, we present an experimental study of unipolar current-induced skyrmion-stripe transformation in a Pt/Co/Fe/Ir magnetic bilayer. High current density pulses induce a densely packed skyrmion state, as commonly reported in many other studies, and skyrmion nucleation is expected to lessen with diminishing current density. However, at a lower current density where pinning effects become significant, a regime where currentinduced skyrmion annihilation and skyrmion-to-stripe transformation is observed. Kerr imaging reveals that, under a low current pulse, the rapidly expanding stripes crowd out and annihilate the skyrmions before quickly decaying and leaving behind a sparse skyrmion population. Our findings establish an additional requirement of a minimum operating current density in the design of skyrmionic devices to avoid unintended skyrmion deletion. On the other hand, this skyrmion annihilation can also be strategically employed as a technique for skyrmion density control using solely current modulation in future skyrmionic devices.

The use of voltage-controlled magnetic anisotropy (VCMA) via the creation of a sloped electric field has been hailed as an energy-efficient approach for domain wall (DW) propagation. However, this method suffers from a limitation of the nanowire length which the DW can propagate on. Here, we propose the use of multiplexed gate electrodes to propagate DWs on magnetic nanowires without having any length constraints. The multi-gate electrode configuration is demonstrated using micromagnetic simulations. This allows controllable voltages to be applied to neighboring gate electrodes, generating large strength of magnetic anisotropy gradients along the nanowire, and the results show that DW velocities higher than 300 m/s can be achieved. Analysis of the DW dynamics during propagation reveals that the tilt of the DW and the direction of slanted gate electrode greatly alters the steady state DW propagation. Our results show that chevron-shaped gate electrodes is an effective optimisation that leads to multi-DW propagation with high velocity. Moreover, a repeating series of high-medium-low magnetic anisotropy regions enables a deterministic VCMA-controlled high velocity DW propagation.