[en] EuO is a ferromagnetic semiconductor with a Curie temperature (T_C) of 69 K. Large magneto-optical effects such as a specific Faraday rotation of 5 x 10⁵ degrees per cm were reported making this compound an interesting starting material for research and applications in the field of magneto-optics. We report on our measurements of the magneto-optical Kerr effect (MOKE) of EuO thin films. EuO thin films were grown on a 50 nm Cr layer on Al₂O₃ substrates by means of molecular beam epitaxy using a distillation technique which allows a precise control of the stoichiometry. The dependence of the Kerr rotation on the film thickness and temperature is investigated

[en] Europiumoxide (EuO) is a ferromagnetic semiconductor with a bandgap of 1.12 eV at room temperature and a Curie temperature of 69 K. In slightly Eu-rich EuO, the magnetic transition is accompanied by a metal-insulator transition with an unprecedented large change in resistivity up to 13 orders of magnitude. Spin-polarized electron spectroscopies revealed that the charge carriers are moving in an essentially fully spin-polarized band. Eu-rich EuO also exhibits an increase of T_C up to 150 K. Similarly, in Gd-doped EuO thin films, T_C can be enhanced up to 170 K with Gd concentration of about 4 %. However, as to whether a MIT occurs in Gd-doped EuO is still an open question. We report our results of in situ measurements of the magnetic and transport properties of EuO thin films prepared by means of molecular beam epitaxy technique in a distillation method which allows a precise control and tuning of the stoichiometry. The connection between the magnetic order and metal-insulator transition of Eu-rich and Gd-doped EuO thin films was investigated

[en] EuO belongs to the rare class of ferromagnetic semiconductors. By electron doping the Curie temperature (T_C) of 69 K for stoichiometric bulk EuO can be enhanced up to 160 K. We report on the growth and characterization of Gd doped EuO thin films. We prepared samples by means of MBE under distillation conditions, which allows a very precise control of the oxygen stoichiometry. Using LEED and RHEED we show that the EuO films can be grown epitaxially and that the [100] directions of the films and MgO substrates are aligned. In order to perform ex-situ measurements we covered the samples with Au and Al capping layers. Using Vibrating Sample Magnetometry we investigated the dependence of T_C on Gd doping and O deficiency. We have observed record high T_C's of 170 K for a Gd concentration of about 4%

[en] Highlights: • Efficiency and limits of polarization dependent HAXPES for solid state systems. • The polarization dependence is less than expected from atomic cross-sections. • Still high contrast (∼20–25) for s orbitals. • Quantitative determination of contributions to the valence band. - Abstract: We have investigated the efficiency and limits of polarization dependent hard X-ray photoelectron spectroscopy (HAXPES) in order to establish how well this method can be used to unravel quantitatively the contributions of the orbitals forming the valence band of solids. By rotating the energy analyzer rather than the polarization vector of the light using a phase retarder, we obtained the advantage that the full polarization of the light is available for the investigation. Using NiO, ZnO, and Cu₂O as examples for solid state materials, we established that the polarization dependence is much larger than in photoemission experiments utilizing ultra-violet or soft X-ray light. Yet we also have discovered that the polarization dependence is less than complete on the basis of atomic calculations, strongly suggesting that the trajectories of the outgoing electrons are affected by appreciable side-scattering processes even at these high kinetic energies. We have found in our experiment that these can be effectively described as a directional spread of ±18° of the photoelectrons. This knowledge allows us to identify, for example, reliably the Ni 3d spectral weight of the NiO valence band and at the same time to demonstrate the importance of the Ni 4s for the chemical stability of the compound