The Control of Cluster-Glass Transition Temperature in Spinel-Type ZnFe₂O4-δ Thin Film

The room-temperature cluster glass state has been realized in zinc ferrite (ZnFe 2 O 4-δ ) thin films using the pulsed-laser-deposition (PLD) method. When the deposition rate was slow about 7 Å/min, the thin film showed antiferromagnetism similar to the bulk zinc ferrite whose Néel temperature was about 20 K. However, by increasing the deposition rate, the magnetization-temperature curve behaved the same as that of cluster glass, and hysteresis between zero-field-cooled and field-cooled magnetization processes was also observed. At higher than 30 Å/min, the cluster glass transition temperature ( T G ) reached approximately room temperature. There are two possibilities for the origin of high- T G cluster glass: 1) spin frustration resulting from the competition of antiferromagnetic interaction between A-B and B-B site iron ions, and 2) random oxygen deficiency. These two factors induced the high-temperature cluster-glass state in zinc ferrite thin films.