title: Valence transition of YbInCu4 observed in hard X-ray photoemission spectra.
abstract: Yb 3d and valence-band photoemission spectra of the first-order valence-transition compound YbInCu4 have been measured with hard x ray at an excitation energy of 5.95 keV. Abrupt changes are clearly observed in both spectra around the transition temperature T(V)=42 K, in comparison with ultraviolet and soft x-ray photoemission (VUV-PES and SX-PES) spectra. From the Yb 3d spectra, the Yb valence has been estimated to be approximately 2.90 from 220 down to 50 K and approximately 2.74 at 30-10 K. We propose that Yb 3d hard x-ray photoemission spectroscopy is a very powerful method to estimate the valence of Yb with high accuracy. On the other hand, the Yb2+ 4f-derived peaks in the valence-band spectra exhibit a remarkable enhancement below T(V). The shape of the valence-band spectra is different from those of the VUV-PES and SX-PES spectra above T(V), reflecting the In 5s and 5p contributions.
authors.affiliation: Hiroshima Synchrotron Radiation Center, Hiroshima University, Kagamiyama 2-313, Higashi-Hiroshima 739-8526, Japan. jinjin@hiroshima-u.ac.jp
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sato
authors.forename: Kenya
authors.initials: K
authors.lastname: Shimada
authors.forename: Masashi
authors.initials: M
authors.lastname: Arita
authors.forename: Koichi
authors.initials: K
authors.lastname: Hiraoka
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kojima
authors.forename: Yukiharu
authors.initials: Y
authors.lastname: Takeda
authors.forename: Kunta
authors.initials: K
authors.lastname: Yoshikawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sawada
authors.forename: Masashi
authors.initials: M
authors.lastname: Nakatake
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Namatame
authors.forename: Masaki
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Takata
authors.forename: Eiji
authors.initials: E
authors.lastname: Ikenaga
authors.forename: Shik
authors.initials: S
authors.lastname: Shin
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Kenji
authors.initials: K
authors.lastname: Tamasaku
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Nishino
authors.forename: Daigo
authors.initials: D
authors.lastname: Miwa
authors.forename: Makina
authors.initials: M
authors.lastname: Yabashi
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ishikawa