Controlling the magneto-transport properties of EuS thin films

The growth of thin films of the ferromagnetic semiconductor EuS on [100] oriented GaAs substrates by electron-beam evaporation is demonstrated. Structural characterization by X-ray diffraction reveals [100] oriented growth. In general, the magnetic and transport properties can strongly be influenced by the deposition parameters. We systematically investigate the influence of the growth temperature T_S in the range T_S=235 K-675 K on the above properties. The Curie temperature increases with decreasing growth temperature, while the magnetic transition becomes broader. The resistivity decreases over four orders of magnitude with decreasing substrate temperature. The behavior of the magnetic properties and the resistivity can be explained by a change in stoichiometry, leading to higher carrier concentrations for lower substrate temperatures. Hall-effect measurements, magnetoresistance, and temperature dependence of the resistivity show a qualitative behavior known from bulk EuS samples. The demonstrated tunability of the magnetic and transport properties opens a wide range of possible applications for EuS in spin-electronics.