Damping of Confined Modes in a Ferromagnetic Thin Insulating Film: Angular Momentum Transfer Across a Nanoscale Field-defined Interface

TL;DR

This study demonstrates that the damping of confined ferromagnetic modes in a thin insulator depends on mode size, revealing interfacial angular momentum transfer mechanisms similar to spin pumping, even in insulating materials.

Contribution

It uncovers size-dependent damping in ferromagnetic insulators caused by interfacial angular momentum transfer, a phenomenon not previously observed in such systems.

Findings

Damping scales with the surface-to-volume ratio of the mode.

Intralayer spin-mixing conductance measured as 5.3 x 10^{19} m^{-2}.

Efficient intralayer angular momentum transfer observed in an insulating ferromagnet.

Abstract

We observe a dependence of the damping of a confined mode of precessing ferromagnetic magnetization on the size of the mode. The micron-scale mode is created within an extended, unpatterned YIG film by means of the intense local dipolar field of a micromagnetic tip. We find that damping of the confined mode scales like the surface-to-volume ratio of the mode, indicating an interfacial damping effect (similar to spin pumping) due to the transfer of angular momentum from the confined mode to the spin sink of ferromagnetic material in the surrounding film. Though unexpected for insulating systems, the measured intralayer spin-mixing conductance $g_{\uparrow \downarrow} = 5.3 \times 10^{19} {\rm m}^{-2}$ demonstrates efficient intralayer angular momentum transfer.