Large spin Hall magnetoresistance and its correlation to the spin-orbit torque in W/CoFeB/MgO structures

摘要

The spin-orbit interaction in heavy metal/ferromagnet/oxide structures hasbeen extensively investigated because it can be employed in manipulation of themagnetization direction by in-plane current. This implies the existence of aninverse effect, in which the conductivity in such structures should depend onthe magnetization orientation. In this work, we report a systematic study ofthe magnetoresistance (MR) of the W/CoFeB/MgO structures and its correlation tothe current-induced torque to the magnetization. We observe that the MR isindependent of the angle between magnetization and current direction, but isdetermined by the relative magnetization orientation with respect to the spindirection accumulated by spin Hall effect, which is the same symmetry ofso-called spin Hall magnetoresistance. The MR of ~1% in W/CoFeB/MgO samples isconsiderably larger than those in other structures of Ta/CoFeB/MgO orPt/Co/AlOx, which indicates a larger spin Hall angle of W. Moreover, thesimilar W thickness dependence of the MR and the current-induced magnetizationswitching efficiency demonstrates that they share the same underlying physics,which allows one to utilize the MR in non-magnet/ferromagnet structure in orderto understand closely related other spin-orbit coupling effects such as inversespin Hall effect, spin-orbit spin transfer torques, etc.