Photoemission study of itinerant ferromagnetCr1−δTe

Abstract

The electronic structures of the itinerant ferromagnets Cr 1Ϫ␦ Te (␦ϭ0.05, 0.25, and 0.375͒ 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 ␦ϭ0.05 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 ␦ϭ0.05 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 ␦ϭ0.05 and 0.375 to explain the spectral weight distribution in the high-binding-energy ͑2-4 eV͒ region in terms of electron-correlation effects. The d-d on-site Coulomb energy is estimated to be significant, Uϳ2 eV, and nearly equal to or smaller than the charge-transfer energy ⌬ϳ2 -3 eV.

Magnetic properties and low temperature X-ray studies of the weak ferromagnetic monoclinic and trigonal chromium tellurides Cr5Te8

“…[6] assumed that m-Cr 5 Te 8 is isostructural to V 5 Te 8 , which according to our investigation can be ruled out [3]. Shimada et al performed photoemission studies on Cr 5 Te 8 and concluded that Cr 5 Te 8 is an itinerant ferromagnet [8]. We note that the sample investigated by this group showed trigonal symmetry with lattice parameters a ¼ 3:924 Å and c ¼ 6:008 Å .…”

“…1 the temperature dependence of the magnetic susceptibilities between 300 and 600 K of m-Cr 5 We note that fitting the data with a modified CurieWeiss law including contributions from temperatureindependent paramagnetism (TIP) always yielded unrealistic negative values for the TIP. This is not surprising since the density of states at the Fermi level is low [8]. Hence, one cannot expect an appreciable Pauli paramagnetic contribution to the susceptibility.…”

“…The pressure dependence of the spontaneous magnetization of Cr 5 Te 8 measured at 4.2 K was reported for a trigonal sample with lattice parameters a ¼ 3:914 Å and c ¼ 5:998 Å [5]. The heat capacities of m-Cr 5 Te 8 and tr-Cr 5 Te 8 show an order-disorder transition of mCr 5 Te 8 to the vacancy ordered Cr 3 Te 4 type structure at 815 K [6,7]. The lattice parameters of m-Cr 5 Te 8 were given with a ¼ 13:535 Å , b ¼ 7:822 Å , c ¼ 11:994 Å and b ¼ 90:4 [6].…”

Electronic structure ofCr1‐δX(X=S,Te)studied by CrYaji1, Kimura2, Hirai3 et al. 2004Phys. Rev. B20060View full textAdd to dashboardCite

“…The electron correlation effects in these "itinerant ferromagnets" Cr 1−δ Te has been discussed with the photoemission spectra. 19 It has been pointed out that the spectral weight in E B =2-4eV observed in the photoemission spectra of Cr 0.95 Te and Cr 3 Te 4 can not be explained by the theoretical band structure calculation, and the intensity at E F is found to be smaller than the theoretical DOS. On the other hand, the spectral weight in E B =2-4eV has been reproduced with the configuration interaction cluster-model calculation, indicating the importance of the electron correlation effect in Cr 1−δ Te.…”

Quasi-Two-Dimensional Ferromagnetism in Cr2Te3and Cr5Te8Crystals

“…Moreover, in Cr-chalcogenides, alterations of the number or the arrangement of Cr-vacancies, as well as the substitution of metal ions, lead to dierent classes of crystals of the Cr 1−x (Te, S, Se) type, with a wide range of many fascinating electrical and magnetic properties. Crystals of these compounds, such as Cr 1−x Te, exhibit antiferromagnetism, non-collinear spin structures, or itinerant electron magnetism [8]. The substitution of Cr atoms with Ti or V creates new properties such as spin-glass [9,10].…”