Electronic structure and magneto-optical Kerr effect of Tm monochalcogenides - art. no. 205112

The optical and magneto-optical (MO) spectra of Tm monochalcogenides are in vestigated theoretically from first principles, using the fully relativisti c Dirac linear combination of muffin-tin orbitals band structure method. Th e electronic structure is obtained with the local-spin-density approximatio n (LSDA), as well as with the so-called LSDA + U approach. In contrast to L SDA, where the stable solution in TmTe is a metal, the LSDA + U gave an ins ulating ground state. LSDA + U theory predicts the thulium ion in TmTe to b e in an integer divalent state. It also shows a gradual decreasing of the e nergy gap with reducing of the lattice constant. LSDA + U theoretical calcu lations produce a similar energy band structure in TmS and TmSe, with twelv e 4f bands fully occupied and hybridized with chalcogenide p states. The 14 th f hole level was found to be completely unoccupied and well above the Fe rmi level and a hole 13th f level is partly occupied and pinned at the Ferm i level. The occupation number of the 13th f level is equal to 0.12 and 0.2 7 in TmS and TmSe, respectively (valence 2.88+ and 2.73+). Such an energy b and structure of thulium monochalcogenides describes well their measured br emsstrahlung isochromat spectroscopy (BIS), and x-ray and ultraviolet photo emission spectra as well as the optical and MO spectra. The origin of the K err rotation realized in the compounds is examined.