Amorphous transition metal oxide films

Abstract

We have been able to prepare amorphous oxides of Fe and Cr by sputter deposition. Magnetization measurements were made between 4.2 K and 300 K. Mössbauer spectra were obtained for the iron oxide samples in the same temperature range. Amorphous CrO₂ films showed no evidence of magnetic order. For the amorphous Fe oxide films, the 4.2 K Mössbauer spectrum showed a broad symmetric six line pattern which collapsed to a doublet at T?100 K. The susceptibility of amorphous iron oxide shows a broad maximum near T=100 K and a paramagnetic moment of only 3μ_β. We present arguments that this behavior cannot be described by superparamagnetism and therefore represents the intrinsic magnetic behavior of amorphous iron oxide.