Ce-doped EuO: Magnetic properties and the indirect band gap

We have prepared and investigated thin films of EuO doped with the rare-earth element cerium. X-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy were used to determine the quality of these films prepared by pulsed laser deposition. Ce doping leads to an enhanced Curie temperature near 150 K, close to that seen for oxygen-deficient EuO1-x. However, the magnetization of Ce-doped EuO exhibits differences from that observed for Gd-doped and oxygen-deficient samples. The high-resolution angular-resolved photoemission from Ce-doped EuO reveals filling of conduction-band states near the X point. This indicates that the band gap in EuO is indirect, and that at 2% doping Ce-doped EuO1-x is at least semimetallic.