Influences of interfacial oxidization on surface magnetic energy, magnetic damping and spin-orbit-torques in Pt / ferromagnet / capping structures

TL;DR

This study explores how different capping layers influence interfacial magnetic properties, damping, and spin-orbit torques in Pt/ferromagnet structures, highlighting the role of interfacial oxides at room temperature.

Contribution

It provides new insights into how interfacial oxides formed by various capping materials affect magnetic anisotropy, damping, and SOT efficiencies in heavy-metal/ferromagnet structures.

Findings

Interfacial oxides significantly affect magnetic anisotropy energy density.

Magnetic damping in Co is notably influenced by MgO capping.

Spin-orbit torque efficiencies vary marginally with different capping layers.

Abstract

We investigate the effect of capping layer (CAP) on the interfacial magnetic anisotropy energy density (K_S), magnetic damping ({\alpha}), and spin-orbit torques (SOTs) in heavy-metal (Pt) / ferromagnet (Co or Py) / CAP (MgO/Ta, HfOx, or TaN). At room temperature (RT) the CAP materials influence the effective magnitude of K_S, which is associated with a formation of interfacial magnetic oxides. The dynamical dissipation parameters of Co are considerably influenced by the CAP (especially MgO) while those of Py are not. This is possibly due to an extra magnetic damping via spin-pumping process across the Co/CoO interface and incoherent magnon generation (spin fluctuation) in the interfacial CoO. It is also observed that both anti-damping and field-like SOT efficiencies vary marginally with the CAP in the thickness ranges we examined. Our results reveal the crucial role of interfacial oxides on the perpendicular magnetic anisotropy, magnetic damping, and SOTs.