Positive exchange bias of EuO1−x films

Abstract We have investigated the magnetic properties of oxygen-deficient europium monoxide EuO1−x films prepared on (0 0 1)-orientation Si single crystal substrate via laser-MBE. Stoichiometric EuO and reduced EuO1−x films are deposited by adjusting the annealing conditions of Si wafers pre-deposition. An enhanced Curie temperature (TC) from 69 K to 150 K is observed by introducing oxygen vacancies to EuO, which is due to the formation of magnetic polarons. The EuO1−x films exhibit positive exchange bias when the films enter the Heisenberg ferromagnetic phase at a lower temperature, which suggests that an antiferromagnetic coupling between the magnetic polarons and Eu2+ 4f spins which is ordered in the typical Heisenberg ferromagnet.