Mössbauer spectroscopic studies on surfaces and thin films

Abstract We have investigated the magnetic properties of surface layers of Fe films using Mossbauer spectroscopy. (110) epitaxial Fe films were made of 56 Fe with appropriate probe layers of 57 Fe in the surface region. In this way we were able to profile the magnetism at and near the surface of our films. Studies of the temperature dependence of layers at the surface indicate a quasilinear dependence of magnetization on temperature while the temperature dependence of layers further inside the material show the usual T 3/2 dependence. In addition to this we note that a region of surface thermal spin deviations larger than bulk values extends over 3 to 4 layers at the surfaces. These results are in qualitative agreement with a number of theoretical studies including those of Mathon. Bender and Hohenberg, and Wolfram et al. The quasilinear temperature dependence of the surface layer implies a weakening of the surface exchange. In addition to the unusual temperature dependence of the surface magnetization we have generally observed larger surface magnetic hyperfine fields near T = 0.