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

TL;DR

This study demonstrates ultra-low current densities for magnetization switching in all-amorphous W-Hf/CoFeB/TaOx films, attributed to low domain wall depinning currents, with potential implications for energy-efficient spintronic devices.

Contribution

It reports the first observation of extremely low switching current densities in all-amorphous W-Hf/CoFeB/TaOx films and links this to low domain wall depinning currents, advancing spintronic material understanding.

Findings

Switching current density as low as 3×10^9 A/m^2.

Low depinning current density correlates with low switching current.

Reference samples show at least an order of magnitude higher critical current densities.

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.