Structural evolution and magnetic properties of Fe/Eu multilayers after thermal annealing

In this paper we report the results of X-ray diffraction (XRD), Eu-151 and Fe-57 conversion electrons Mossbauer spectroscopy (CEMS) at room temperature and magnetization measurements in Fe/Eu multilayers deposited on oxidized Si(1 1 1) wafers. These multilayers were annealed at 320 degrees C for 1-9 h. The as-deposited multilayers were composed of metallic Eu together with the EuO phase and polycrystalline iron. Tn all annealed samples, XRD and Eu-151 GEMS measurements have shown only the Eu2O3 phase. The Fe-57 GEMS shows metallic iron and an unexpected Fe3O4 phase. This phase increases with the annealing time, and after 6 h we had observed clearly an iron oxide paramagnetic phase. The possible origins of this paramagnetic phase are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.