ILEEMS of thin α-Fe2O3 films prepared by RF sputtering

Abstract

Thin α-Fe2O3 films on semi-quartz substrates have been prepared by radio frequency (RF) sputtering of a magnetite target in a pure argon gas flow with a bias power applied. The films were studied by X-ray diffraction and Integral Low-Energy Electron Mössbauer Spectroscopy (ILEEMS), the latter in the temperature range of 80 to 330 K. In ILEEMS electrons of ∼10 eV are detected and therefore it is an ideal instrument to study thin films with thicknesses below 500 nm. The first ILEEMS measurements on α-Fe2O3 films are reported and focus on the behaviour of the Morin transition, i.e., the reorientation of Fe3 + spins from the [111] crystallographic direction at low temperature, to the (111) basal plane at high temperature. Some films (∼400 nm) show the presence of both a weak- and antiferromagnetic hematite phase for all temperatures between 140 and 330 K. Others of about ∼100 nm thick only have a weak ferromagnetic phase for temperatures between 140 and 330 K of which the hyperfine field distribution shows two maxima, related to two distinct phases. Both phases stay in some films almost equal in intensity in the spectrum for the whole measured temperature range. In others a significant evolution in the spectral areas of both weak ferromagnetic phases as function of the temperature is observed.