Electronic and structural properties of equiatomic Co-Pt alloy films at low temperature

Magneto-optical properties of Co-Pt alloy films were investigated at low and room temperatures. We also investigated atomic and electronic structures of these films. The saturated polar Kerr rotation angles of CoPt and CoPt3 alloy films show different temperature dependence. Synchrotron-radiation photoemission spectroscopy was employed to confirm the correlation between the magneto-optical properties and the electronic structures of these films. Changes of a peak at 4.3 eV relevant to the Pt 5d levels hybridized with Co 3d electrons of the CoPt film and of the valence-band shape upon cooling have the same trend as that of the saturated Kerr rotation angle. A structural phase transition of the CoPt film from the tetragonal L1(0) to orthorhombic phase upon cooling is suggested by the theoretical calculations using linearized-muffin-tin-orbitals methods within the so-called "LDA + U" scheme as well as the experimental observations. X-ray diffraction patterns before and after cooling also support this structural phase transition. (C) 2000 American Institute of Physics. [S0021-8979(00)05804-7].