Crystal field effects on spin pumping

TL;DR

This paper investigates how crystal field effects influence spin pumping at insulator|metal interfaces, revealing anisotropic spin currents and dependence on crystal orientation, with implications for spintronic device design.

Contribution

It demonstrates that crystal fields induce anisotropy in spin currents and modifies the spin mixing conductance based on crystal orientation, a novel insight into interface effects.

Findings

Crystal fields cause anisotropic spin currents.

Spin mixing conductance depends on crystal cut and orientation.

Interface effective field relates to coherent spin density motion.

Abstract

"Spin pumping" is the injection of spin angular momentum by a time-dependent magnetization into an adjacent normal metal proportional to the spin mixing conductance. We study the role of electrostatic interactions in the form of crystal fields on the pumped spin currents generated by insulators with exchange-coupled local moments at the interface to a metal. The crystal field is shown to render the spin currents anisotropic, which implies that the spin mixing conductance of insulator|normal metal bilayers depends on crystal cut and orientation. We interpret the interface "effective field" (imaginary part of the spin mixing conductance) in terms of the coherent motion of the equilibrium spin density induced by proximity in the normal metal.