Characterizing the phase purity of nanocrystalline Fe3O4 thin films using Verwey transition

Abstract

We have employed Verwey transition as a probe to check phase purity of nanocrystalline Fe3O4 films grown at different substrate temperatures (Ts) by means of magnetization study. The drop in magnetization at temperatures other than Verwey transition temperature Tv (120K), in the low and high Ts films indicates the presence of antiferromagnetic (α-Fe2O3/FeO) impurity phases. After wet H2 reduction treatment on these films, a vibrant appearance of Verwey transition is observed which confirms Fe3O4 phase at all Ts. However, high Ts films exhibit low Tv value with distribution, Tv±ΔTv=112+25K emanating from residual magnetic phases, which were not traced by XRD studies. Interestingly, these nanocrystalline Fe3O4 films exhibit anisotropic magnetic behaviors above Tv, similar to the single crystal Fe3O4. Below the saturation field, the easy (111) and relatively hard (110) axis of magnetizations align along their texture planes.