Preparation of Gd-doped EuO_{1 <i>x</i>}thin films and the magnetic and magneto-transport properties

Abstract

Polycrystalline europium monoxide (EuO) films doped with and without Gd were prepared using a reactive deposition method in a MBE system. Two different electron doping methods, Gd substitution and oxygen deficiency, enhance the Curie temperature (TC) and the temperature dependence of magnetization differently. Gd doping increases TC up to 125 K, while oxygen deficient samples enhance it above 150 K. The enhanced TC is attributed to the increase in the indirect exchange interaction between Eu2+ spins via conduction electrons. The resistivities as a function of temperature for both quasi-stoichiometric (QS) EuO and QS-GdxEu1−xO show maxima near 70 and 110 K, respectively. The conduction band magnetic splitting explains the resistivity behaviours. Both the temperature dependences of the large magneto-resistance and the absorption edge are also interpreted by the conduction band magnetic splitting mechanism. The unusual blue shift observed in Gd-doped samples is not yet understood.