Photoemission study of itinerant ferromagnet Cr1- delta Te.

Abstract

The electronic structures of the itinerant ferromagnets ${\mathrm{Cr}}_{1\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$Te (\ensuremath{\delta}=0.05, 0.25, and 0.375) have been studied by photoemission spectroscopy. The valence-band spectra are compared with the density of states given by band-structure calculations. In spite of the itinerant nature of the d electrons, disagreement between the photoemission spectra and the band-structure calculations exists in the magnitude of the d-band exchange splitting and the spectral weight at the Fermi level and 2--4 eV below it: The occupied d band for \ensuremath{\delta}=0.05 is shifted away from the Fermi level; the observed spectral weight at the Fermi level is significantly suppressed compared with the band-structure calculations for \ensuremath{\delta}=0.05 and 0.375, where the nominal d-electron numbers are close to integers 4 and 3, respectively. Configuration-interaction cluster-model calculations have been made for \ensuremath{\delta}=0.05 and 0.375 to explain the spectral weight distribution in the high-binding-energy (2--4 eV) region in terms of electron-correlation effects. The d-d on-site Coulomb energy is estimated to be significant, U\ensuremath{\sim}2 eV, and nearly equal to or smaller than the charge-transfer energy \ensuremath{\Delta}\ensuremath{\sim}2--3 eV. \textcopyright{} 1996 The American Physical Society.