Giant Anisotropy of Charge-to-Spin Conversion in Fe Films with Fourfold-Symmetric Anisotropy

Abstract

Manipulating charge-to-spin conversion in a single magnetic layer holds great promise for optimizing efficiency of spintronic devices. Here we present experimental evidence uncovering a giant conversion anisotropy of up to 400% in fourfold-symmetric anisotropy $\mathrm{Fe}$ films on $\mathrm{Mg}\mathrm{O}(100)$ substrate by changing the direction of applied radio frequency microwave currents from the magnetic hard axis to the easy one. Together with the anisotropy of Gilbert damping and anisotropic magnetoresistance, the fourfold-symmetric anisotropy is found to stem from large emergent spin-orbit coupling in $\mathrm{Fe}$ films with local lattice distortions, which is further confirmed by selected area electron diffraction patterns in different regions. Given that $\mathrm{Fe}$ films are deposited by magnetron sputtering at room temperature, our results suggest a simple route for designing future energy-efficient magnetic devices for mass production.