Tunable exchange bias in Y$_3$Fe$_5$O$_{12}$ film on Gd$_3$Ga$_5$O$_{12}$

TL;DR

This study demonstrates tunable exchange bias in Y$_3$Fe$_5$O$_{12}$ films on Gd$_3$Ga$_5$O$_{12}$, showing that interface spin dynamics near the blocking temperature can be controlled via field cooling protocols.

Contribution

It reveals that sputtering-grown Y$_3$Fe$_5$O$_{12}$ films exhibit a lower, tunable exchange bias due to complex interface spin dynamics, expanding understanding of exchange bias control.

Findings

Blocking temperature reduced to about 7 K.

Exchange bias can be tuned by field cooling protocols.

Interface spin dynamics resemble a spin glass.

Abstract

Ferrimagnetic Y$_3$Fe$_5$O$_{12}$ grown on the (001) surface of paramagnetic Gd$_3$Ga$_5$O$_{12}$ experiences an exchange bias field, which has been attributed to the magnetism of an interface layer between the two materials. We report here that when grown using sputtering and with lower post-annealing temperatures than in previous works, the blocking temperature of the interface magnetic layer is lowered to about 7 K, while still displaying a strong exchange bias. This exchange bias is then found to be tunable between its two extreme values by carefully varying the field cooling protocol. This is attributed to a slow and complex dynamics of the spins of the interface-layer when it is warmed up close to its blocking (or melting) temperature, which is reminiscent of a spin glass.