Electronic structure of Gd5(Si, Ge)4

Abstract

The electronic structure of the compounds Gd 5 (Si, Ge) 4 has been investigated with the use of x-ray and ultraviolet photoelectron spectroscopies. The results are compared with calculations performed with the tight-binding linear muffintin orbital method for Gd 5 Si 4 and Gd 5 Ge 4 . Very good agreement with the experimental data has been obtained and conclusions about the character of the electronic states, their hybridization and their influence on magnetic and electrical properties have been drawn. The effect of Ti substitution (5 at.%) for Si or Ge in Gd 5 (Si, Ge) 4 has been investigated. Significant changes in the electronic structure near the Fermi level have been found especially for Gd 5 Si 4 .

Electron energy loss spectroscopy of Gd compounds

“…The features at loss energies 21-27 eV should be related to the structure of the unoccupied Gd 5d band. However, the calculations [5,6] show that such relatively broad band is formed for all compounds. The resonance transitions from the Gd 5p level requires empty states above the Fermi level and such states are present independently of the compound.…”

“…All investigated compounds are metallic except Gd 5 Ge 4 , which shows partly semiconducting-like resistivity. However, calculations of the electronic structure [5,6] indicated to relatively large density of states at the Fermi level for all compounds. The plasmon energies obtained from the free electron model are: 11.1 eV for Gd, 13.1 eV for GdTiGe, 13.9 eV for Gd 5 Ge 4 and Gd 5 Si 2 Ge 2 and 15.0 eV for GdTiSi.…”

“…For lower energies when the electron escape depth path is only severalÅ, the surface relaxation may be a reason for the observed smaller ω p values. All investigated compounds have a layered types of crystallographic structure [5,6] and one can expect a considerable surface relaxation. The observed plasmons for low E p would be then not only an effect of surface excitation but also can contain contribution from the reconstructed bulk.…”

“…In our previous studies, we investigated both experimentally and theoretically their electronic structure using photoelectron spectroscopy and LMTO calculations [5,6]. GdTiGe shows the highest ferromagnetic transition temperature for a Gd compounds with non-magnetic elements T C = 374 K [5] whereas GdTiSi exhibits a Curie temperature around room temperature.…”

Spectroscopic ellipsometry study of optical anisotropy inGd5Si2Ge2and comparison with reflectance difference spectra

“…17,18 The states centered about 0.5 eV below the Fermi energy are due to Gd-Gd bonds or Gd 5d bands. From a comparison with the measured optical conductivity of Gd, 19,20 the low-energy ͑ϳ2 eV͒ optical transitions are primarily from Si͑Ge͒ 3p͑4p͒-based bands to bands based on Gd 5d states.…”