Sign reversal of spin–orbit torque induced by interfacial antiferromagnetic coupling

Abstract

Nonmagnetic-metal/ferromagnetic heterostructures have drawn extensive attention due to the generation of spin–orbit torque (SOT). This work is based on the large spin Hall angle observed in Pt0.70(GdOy)0.30 composite films, we focus on investigating the sharp sign reversal of the damping-like SOT induced by antiferromagnetic coupling at the NiFe/Pt1−x(GdOy)x (x ≥ 0.30) interface. Such interface-modulated SOT is found to be suppressed by inserting an ultra-thin copper spacer layer using spin-torque ferromagnetic resonance. Meanwhile, the relevant interfacial parameters further indicate the key importance of interfacial magnetic coupling for boosting spin transport efficiency. The superconducting quantum interference device tests on NiFe/Pt1−x(GdOy)x (x ≥ 0.30) structures reveal that the magnetization in Pt1−x(GdOy)x is antiparallel to that of NiFe, forming an antiferromagnetically coupled configuration at the NiFe/Pt1−x(GdOy)x interface. Our results highlight the promising application of rare earth materials in spin transport, and the construction of interfacial antiferromagnetic coupling opens a route to modulate SOT.