Ferrimagnetic ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ grown on the (001) surface of paramagnetic ${\mathrm{Gd}}_3{\mathrm{Ga}}_5{\mathrm{O}}_{12}$ 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 postannealing temperatures than in previous works, the blocking temperature of the interface magnetic layer of a micron-sized film sample 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 varying the field cooling protocol. This is attributed to a slow and complex dynamics of the frustrated spins in the interface layer when the sample is warmed up close to the blocking (or melting) temperature.

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• Exchange bias
• Magnetic insulators
• Magnetic thin films
• Magnetization measurements