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

We have employed Verwey transition as a probe to check phase purity of nanocrystalline Fe₃O₄ films grown at different substrate temperatures (T_s) by means of magnetization study. The drop in magnetization at temperatures other than Verwey transition temperature T_v (120 K), in the low and high T_s 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 T_s. However, high T_s films exhibit low T_v value with distribution, T_v±ΔT_v=112+25 K emanating from residual magnetic phases, which were not traced by XRD studies. Interestingly, these nanocrystalline Fe₃O₄ films exhibit anisotropic magnetic behaviors above T_v, 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. - Highlights: • Verwey transition can be a potential probe for phase purity check of Fe₃O₄ films. • Wet H₂ reduction can produce Fe₃O₄ films with various textures. • Magnetic anisotropic behavior alike to the single crystal Fe₃O₄ has been observed.