  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.
