Mössbauer and magnetic study of rf-sputtered Fe2O3 films

Abstract

We report Mössbauer and magnetic susceptibility data as a function of temperature for a thin film prepared by rf-sputtering from an Fe3O4 target in an O2-Ar atmosphere. Powder X-ray diffraction data shows very broad bands at d = 2.7, 2.0 and 1.5 Å. The magnetic susceptibility data as a function of temperature may be divided into three regions. The low temperature region (T<170 K) shows a near constant susceptibility of 1.5×10−4 emu/g. Between 170 and 225 K there is a dip in the susceptibility. For T≳225 K the susceptibility decreases with temperature in accord with the Curie Weiss law. We have estimated the Neel temperature to be 220 K from the peak in the magnetic susceptibility and the collapse of the magnetic hyperfine splitting in the Mössbauer data. While the film discussed in the present paper is amorphous, we have found that films sputtered at slightly higher power levels consist of microcrystals of γFe2 O3.