Exchange bias and training effect in an amorphous Zn-Fe-O/nanocrystalline GaFeO3 bilayer thin film

In this paper, I report the exchange bias effect in a bilayer thin film of amorphous Zn-Fe-O (ZFO) and nanocrystalline GaFeO₃ (GFO). I deposited the amorphous ZFO layer on top of a nanocrystalline GFO thin film using pulsed laser ablation of a Zinc ferrite (ZnFe₂O₄) target at room temperature. This bilayer film showed a large exchange bias effect (H_E ∼ 418 Oe at 2 K). The exchange bias shift decreased exponentially as the temperature increased and disappeared for T > 30 K. Along with the exchange bias shift, the film also showed enhanced magnetization in Field Cooled (FC) measurements as compared to the Zero Field Cooled (ZFC) magnetization. The magnetization decreased during consecutive M-H loops cycling in training effect measurements. This decrease in the magnetization of the film followed the spin configurational relaxation model. The observed exchange bias effect can be attributed to a unidirectional anisotropy originated due to the pinning effect of the interfacial spins of the ZFO layer.