Influence Of The Island Structure On The Magnetic-Properties Of Quasi-2-Dimensional Fe Films

Reported reductions of Curie temperature and a linear temperature dependence of magnetization in quasi-two-dimensional magnetic films has generated significant interest in the past decade. We have made several Fe(110)/Ag(111) superlattices by molecular-beam epitaxy with the Fe component 2 monolayers thick and the Ag component of various thicknesses. By taking Mössbauer spectroscopy measurement in an external field, we found that a central feature in the Mössbauer spectrum at high temperature may not relate to the reduction of Curie temperature, but instead comes from the thermal relaxation of small islands in the Fe film. The magnetic hyperfine field has a linear temperature dependence, and this is explained by a simple relaxation model based on the island structure. This model is also supported by studying superlattices grown with different conditions.