Ultra-low switching current density in all-amorphous W-Hf / CoFeB / TaOx films

Abstract

We study current-induced deterministic magnetization switching and domain wall motion via polar Kerr microscopy in all-amorphous W${}_{66}$Hf${}_{34}$/CoFeB/TaO${}_{\text{x}}$ with perpendicular magnetic anisotropy and large spin Hall angle. Investigations of magnetization switching as a function of in-plane assist field and current pulse-width yield switching current densities as low as $3\times 10^9$ A/m${}^2$. We accredit this low switching current density to a low depinning current density, which was obtained from measurements of domain wall displacements upon current injection. This correlation is verified by investigations of a Ta/CoFeB/MgO/Ta reference sample, which showed critical current densities of at least one order of magnitude larger, respectively.

9 pages, 8 figures