Thickness-dependent anisotropic Gilbert damping in heterostructures of ferromagnets and two-dimensional ferroelectric bismuth monolayer

TL;DR

This study uses first-principles calculations to explore how the Gilbert damping parameter varies with thickness and orientation in Fe films interfaced with a bismuth monolayer, revealing strong interfacial spin-orbit effects.

Contribution

It uncovers the non-monotonic thickness-dependent anisotropic Gilbert damping in Bi/Fe heterostructures caused by interfacial and intrinsic spin-orbit couplings.

Findings

Enhanced Gilbert damping due to interfacial SOC.

Non-monotonic damping anisotropy with thickness.

Anisotropic band structures linked to SOC effects.

Abstract

The Gilbert damping parameter, which describes magnetization dynamics, is crucial for the performance of modern spintronic devices, affecting factors such as the switching speed and critical current density of magnetoresistive random access memory. Thus, the ability to engineer it on demand is pivotal for developing novel spintronic applications. In this work, we systematically examine the Gilbert damping parameter of Fe films in contact with a black phosphorus-like bismuth monolayer using first-principles calculations. In these Bi/Fe heterostructures, we obtain a significantly enhanced Gilbert damping owing to strong interfacial spin-orbit couplings (SOCs). Interestingly, we find non-monotonic thickness-dependent Gilbert damping anisotropy and attribute that to the competition between the interfacial SOC and the intrinsically anisotropic SOC of Fe films. We further demonstrate that these SOC effects lead to anisotropic band structures, which are responsible for the anisotropic Gilbert damping. Our work provides a deep understanding of the anisotropic Gilbert damping and opens avenues for exploring it in ferromagnetic heterostructures.