Microscopic origin of the magneto-optical properties of CoPt alloys - art.no. 125105

The microscopic origin of the magneto-optical (MO) properties of CoxPt1-x a lloys is studied on the basis of Kerr effect measurements and first-princip les band-structure calculations in a wide range of photon energy ((h) over bar omega = 0.75-5.8 eV) and Co content (x = 0.03-0.5). Spin-polarized rela tivistic linear-muffin-tin-orbital (LMTO) calculations performed within the local density approximation and supercell approach reproduce well the spec tral shape of the measured off-diagonal optical conductivity tensor compone nts. Using the ab initio LMTO band-structure calculations, the band-by-band and k-space decompositions as well as the analysis of the magneto-optical transitions between electronic states localized in different energy regions are performed. It is found that for the alloys studied the uv part of the MO spectra with a pronounced peak at 4 eV photon energy comes from optical transitions between initial and final states located within well-defined en ergy intervals that are very close to those obtained for fcc Pt metal in ex ternal magnetic field. The correlation between the band structure of the al loys and the energy dependence of their MO spectra is investigated. The imp ortance of the spin-orbit interaction for the transitions in different ener gy regions is demonstrated by calculating the state- and site-projected den sity of the expectation value of the orbital moment. The evolution of the e lectronic structure of Co-Pt alloys with the increase of Co content and the influence of the hybridization between the Co and Pt electronic states are analyzed and discussed.