Independence of spin-orbit torques from the exchange bias direction in Ni$_{81}$Fe$_{19}$/IrMn bilayers

TL;DR

This study shows that spin Hall angles in Ni$_{81}$Fe$_{19}$/IrMn bilayers are unaffected by the exchange bias direction, indicating independence between spin-orbit torques and exchange bias orientation.

Contribution

It demonstrates experimentally that spin Hall angles in Ni$_{81}$Fe$_{19}$/IrMn are independent of exchange bias direction, providing new insights into spin-orbit torque mechanisms.

Findings

Spin Hall angles are approximately 2.8% regardless of orientation.

No correlation found between exchange bias direction and spin Hall angle.

Spin-orbit torques are independent of exchange bias in these bilayers.

Abstract

We investigated a possible correlation between spin Hall angles and exchange bias in Ni$_{81}$Fe$_{19}$/IrMn samples by performing spin torque ferromagnetic resonance measurements. This correlation is probed by patterning of Ni$_{81}$Fe$_{19}$/IrMn bilayers in different relative orientations with respect to the exchange bias direction. The measured voltage spectra allow a quantitative determination of spin Hall angles, which are independent of the orientation around 2.8\pm0.3%.