Increased Gilbert damping in Yttrium Iron Garnet by low temperature vacuum annealing

TL;DR

This study demonstrates that low-temperature vacuum annealing significantly increases the Gilbert damping in yttrium iron garnet, affecting spin pumping measurements, while annealing in oxygen does not produce this effect.

Contribution

It reveals the impact of vacuum annealing on YIG's damping, highlighting the importance of surface treatment conditions in spintronic device performance.

Findings

Vacuum annealing at 300°C increases damping by a factor of 8.

Oxygen annealing at the same temperature does not change damping.

Surface cleaning conditions critically influence magnetic damping in YIG.

Abstract

The effect of thermal surface cleaning on the Gilbert damping, $\alpha$, of yttrium iron garnet (YIG), before capping with a metallic layer, has been investigated. Our results show that $\alpha$ is strongly effected by relatively mild annealing conditions (T = 300 C) when performed in a vacuum. This increase needs to be taken into account when obtaining the spin mixing conductance from spin pumping measurements. We measure an increase in $\alpha$ by a factor of 8 when the YIG is vacuum annealed at 300 C. No such changes in $\alpha$ are observed when annealed at the same temperature in 0.1 mbar of oxygen.