Effects of the stoichiometry and chemical order on the electronic structure and magnetic properties of Cr-Pt alloys probed by angular-resolved photoemission

The electronic structure of the intermetallic compound CrPt3 is studied by angle-resolved ultraviolet photoemission spectroscopy on (001) and (111) surfaces of molecular-beam-epitaxy-grown epitaxial films in the photon energy range of 21-150 eV. The surface structures and the chemical order are investigated by reflecting high-energy electron diffraction. The partial density of states of CrPt3 has been estimated using the photoionization dependence of the photoemission. The momentum dependence of the valence-band energies is determined for the Gamma-R bulk high-symmetry line and the Gamma-M and R-X directions using synchrotron radiation. The nature of these bands was identified by a comparison with band-structure calculations based on density-functional theory in the local spin-density approximation. A good agreement between measured and ab initio calculated energy bands is found. Band mapping has also been performed using the angle-variation method on (001) surfaces excited by the He I emission line. For variations of the degree of surface order, a simple relationship between the electronic structure and magnetic properties of the alloy is found, which is discussed in terms of a modeled band structure. The magnetic anisotropy of this alloy is found to relate to the density of states at the Fermi level as determined by photoemission.