Field and temperature dependence of the magnetization in ferromagnetic EuO thin films

Ferromagnetic EuO exhibits a metal-insulator transition showing a very large colossal magneto-resistance. Recently, it became possible to grow epitaxial films of EuO_1-x on Si with spin polarization above 90%. The direct integration of EuO with Si will allow the fabrication of model systems for studying devices in the field of spintronics. In order to determine non-destructively the magnetic properties of thin films of EuO on Si, we have measured the critical angle of reflection by using polarized neutrons. The results confirm that the magnetic moment in the films is consistent with the bulk value. In addition, we show that the change of magnetization is not caused by repopulation of domains but by domain rotation.