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 3μβ. We present arguments that this behavior cannot be described by superparamagnetism and therefore represents the intrinsic magnetic behavior of amorphous iron oxide.