Magnetism and transport of CuCr2Se4 thin films

We report on the successful synthesis, magnetism and transport of highly spin-polarized chalcogenide thin films of CuCr2Se4, which are promising candidates for spin-based electronic applications. We also present electronic structure calculations for CuCr2Se4 that, together with magnetic and transport data, imply that the stoichiometric compound is a metallic ferromagnet with a relatively low density of hole-like carriers at the Fermi energy. These calculations also predict that a deficiency of Se will deplete the minority density of states at the Fermi energy perhaps leading to a half-metal. We have successfully grown thin films of CuCr2Se4 by pulsed laser deposition on isostructural MgAl2O4 substrates followed by an anneal in a Se-rich environment. X-ray diffraction confirms the structure of CuCr2Se4 on MgAl2O4 substrates as well as a secondary phase of Cr2Se3. X-ray absorption spectroscopy indicates that the chemical structure at the surface of the films is similar to that of bulk CuCr2Se4 single crystals. Magnetization measurements indicate that these films saturate with a magnetic moment close to 5 mu(B)/f.u. and a Curie temperature ( T-c) above 400 K. X-ray magnetic circular dichroism measurements show that magnetic order persists to the surface of the film. Resistivity and Hall effect measurements are consistent with p-type ferromagnetic metallic behavior and with the electronic structure calculations. (C) 2007 Elsevier B.V. All rights reserved.