Spin-orbit torques are studied in Ta/TbFeCo patterned structures with a bulk perpendicular magnetic anisotropy (bulk-PMA) for the first time. The current-induced magnetization switching is investigated in the presence of a perpendicular, longitudinal, or transverse field. In order to rule out Joule heating effect, switching of the magnetization is also demonstrated using current pulses.It is found that the anti-damping torque correlated with spin Hall effect is very strong, and a spinHall angle of about 0.12 is obtained. The field-like torque related with Rashba effect is negligib le in this structure suggesting that the interface play a significant role in Rashba-like torque.

No abstract

Spin Hall effect (SHE) induced reversal of perpendicular magnetization has attracted significant interest, due to its potential to lead to low power memory and logic devices. However, the switching requires an assisted in-plane magnetic field, which hampers its practical applications. Here, we introduce a novel approach for external-field-free spin Hall switching of a perpendicular nanomagnet by utilizing a local dipolar field arising from an adjacent in-plane magnetic layer.Robust switching of perpendicular CoFeB nanopillars in a dipole-coupled composite stack is experimentally demonstrated in the absence of any external magnetic field, in consistent with the results of micromagnetic simulation. Large in-plane compensation field of about 135 Oe and outof-plane loop shift of about 45 Oe / 10 7 A•cm -2 are obtained in the nanopillar devices with composite structure. By performing micromagnetic simulations, we confirm the composite external-field-free switching strategy can also work for a 10 × 10 nm 2 circular pillar. Compared with other proposed methods for external-field-free spin Hall switching of perpendicular magnetization, the dipolecoupled composite structure is compatible with a wide range of spin Hall systems and perpendicular magnetic tunnel junctions, paving the way towards practical SHE-based MRAM and logic applications. This file includes: Section S1. Results for composite nanopillars with IPL // x.  Section S2. Results for composite nanopillars with different aspect ratios.  Section S3. Coercive field and thermal stability of IPL.  Section S4. Calculation of stray field for 300 × 150 nm 2 nanopillar.  Section S5. Micromagnetic simulation of SH switching process for 300 × 150 nm 2 elliptical nanopillar under a uniform in-plane field.  Section S6. Micromagnetic simulation of external-field-free SH switching for 10 × 10 nm 2 composite nanopillar

The spin orbital torques in Ta/CoFeB/MgO structures are experimentally investigated utilizing the planar Hall effect and magnetoresistance measurement. By angular field characterization of the planar Hall resistance at ±current, the differential resistance which is directly related to the spin orbital torques is derived. Upon curve fitting of the analytical formulas over the experimental results, it is found that the anti-damping torque, also known as spin Hall effect, is sizable while a negligible field-like torque is observed. A spin Hall angle of about 18 ± 0.6% is obtained for the Ta layer. Temperature dependent study of the spin orbital torques is also performed. It is found that temperature does not significantly modify the spin Hall angle. By cooling down the sample down to 100 K, the obtained spin Hall angle has a maximum value of about 20.5 ± 0.43%.

No abstract

The processional magnetization induced spin current at the interface between CoFeB and Ta has been studied experimentally using spin pumping and inverse spin Hall effect for different thicknesses of CoFeB film down to 1.6 nm. It is found that upon decreasing the thickness of the CoFeB, the frequency of the peak position of the spin pumping signal reduces and dispersion relation of the ferromagnetic resonance changes from a quadratic to a linear behavior indicating the presence of an interfacial perpendicular anisotropy. Furthermore, a nonreciprocal behavior between the spin pumping signal amplitude at positive and negative fields is observed which could be as large as 100%. Our experimental results suggest reduction of the effective demagnetization field and possibly the spin waves nonreciprocal behavior mediated by the Dzyaloshinskii-Moriya interaction at the Ta/CoFeB interface are responsible for the large nonreciprocity of the spin pumping signal.

No abstract

No abstract