Strain-enhanced spin-orbit coupling in permalloy thin films

A comprehensive analysis of the impact of strain on spin-orbit coupling (SOC) in permalloy (Py, $\mathrm{N}{\mathrm{i}}_{80}\mathrm{F}{\mathrm{e}}_{20}$) thin films is presented. Utilizing a combination of ferromagnetic resonance (FMR) and x-ray magnetic circular dichroism (XMCD) techniques, we systematically evaluate the modifications in SOC as a function of applied strain. Our FMR data indicate a marked enhancement in Gilbert damping and an increase in the perpendicular magnetic anisotropy constant, suggesting that SOC strength intensifies with both compressive and tensile strains. XMCD results, in concert with first-principles calculations, elucidate the underlying mechanism: strain-induced lattice distortions substantially elevate the orbital moments within the Py films. This boost in the orbital moment is attributed to the strain's modulation of the orbital quenching effect, revealing a direct correlation between lattice strain and SOC enhancement. These insights not only deepen our understanding of SOC in ferromagnetic thin films but also have potential implications for the design of spintronic devices where controlling SOC is paramount.