Experimental and theoretical analysis of magnetic moment enhancement in oxygen-deficient EuO

We have carried out both experimental and theoretical studies of the magnetic properties of thin films of oxygen-deficient EuO. Accurate control of the oxygen vacancy concentration in these films was achieved by sputter codeposition of Eu and Eu(2)O(3). The films were characterized by superconducting quantum interference device, x-ray reflectometry and polarized neutron reflectometry and the magnetic moment was found to increase monotonically with oxygen vacancy concentration. The electronic structure of EuO(1-x) was calculated using density-functional theory (DFT+U). In agreement with previous studies, these calculations show that oxygen vacancies act as n-type dopants in EuO and that the excess electrons preferentially populate the majority spin branch of the spin-polarized conduction band. The observed increase in the magnetic moment originating from these excess electrons was accurately determined experimentally and found to be in good agreement with our quantitative predictions.