Preparation of Gd-doped EuO1−x thin films and the magnetic and magneto-transport properties

Abstract

Polycrystalline europium monoxide (EuO) films doped with and without Gd were preparedusing a reactive deposition method in a MBE system. Two different electron dopingmethods, Gd substitution and oxygen deficiency, enhance the Curie temperature(TC) and the temperature dependence of magnetization differently. Gd doping increasesTC up to 125 K, while oxygen deficient samples enhance it above 150 K. The enhancedTC is attributed to the increase in the indirect exchange interaction betweenEu2+ spins viaconduction electrons. The resistivities as a function of temperature for both quasi-stoichiometric (QS) EuOand QS-GdxEu1−xO show maxima near 70 and 110 K, respectively. The conduction band magnetic splittingexplains the resistivity behaviours. Both the temperature dependences of the largemagneto-resistance and the absorption edge are also interpreted by the conduction bandmagnetic splitting mechanism. The unusual blue shift observed in Gd-doped samples is notyet understood.