Effect of interfacial oxidation layer in spin pumping experiments on Ni80Fe20/SrIrO3 heterostructures

Abstract

SrIrO3 with its large spin–orbit coupling and low charge conductivity has emerged as a potential candidate for efficient spin–orbit torque magnetization control in spintronic devices. Here we report on the influence of an interfacial oxide layer on spin pumping experiments in Ni80Fe20 (NiFe)/SrIrO3 bilayer heterostructures. To investigate this scenario, we have carried out broadband ferromagnetic resonance (BBFMR) measurements, which indicate the presence of an interfacial antiferromagnetic oxide layer. We performed in-plane BBFMR experiments at cryogenic temperatures, which allowed us to simultaneously study dynamic spin pumping properties (Gilbert damping) and static magnetic properties (such as the effective magnetization and magnetic anisotropy). The results for NiFe/SrIrO3 bilayer thin films were analyzed and compared to those from a NiFe/NbN/SrIrO3 trilayer reference sample, where a spin-transparent, ultra-thin NbN layer was inserted to prevent the oxidation of NiFe. At low temperatures, we observe substantial differences in the magnetization dynamics parameters of these samples. In particular, the Gilbert damping in the NiFe/SrIrO3 bilayer sample drastically increases below 50K, which can be well explained by enhanced spin fluctuations at the antiferromagnetic ordering temperature of the interfacial oxide layer. Our results emphasize that this interfacial oxide layer plays an important role for the spin current transport across the NiFe/SrIrO3 interface.