Temperature dependent Eu 3d-4f X-ray Absorption and Resonant Photoemission Study of the Valence Transition in $EuNi_2(Si_{0.2}Ge_{0.8})_2$

K. Yamamoto; K. Horiba; M. Taguchi; M. Matsunami; N. Kamakura; A. Chainani; Y. Takata; K. Mimura; M. Shiga; H. Wada; Y. Senba; H. Ohashi; S. Shin

doi:10.1103/PhysRevB.72.161101

paper

Temperature dependent Eu 3d-4f X-ray Absorption and Resonant Photoemission Study of the Valence Transition in $E u N i_{2} (S i_{0.2} G e_{0.8})_{2}$

arXiv:cond-mat/0507520 · doi:10.1103/PhysRevB.72.161101

Abstract

We study the mixed valence transition ( $T$ $_{v}$ $\sim$ 80 K) in EuNi $_{2}$ (Si $_{0.2}$ Ge $_{0.8}$ ) $_{2}$ using Eu 3 $d - 4 f$ X-ray absorption spectroscopy (XAS) and resonant photoemission spectroscopy (RESPES). The Eu $^{2 +}$ and Eu $^{3 +}$ main peaks show a giant resonance and the spectral features match very well with atomic multiplet calculations. The spectra show dramatic temperature ( $T$ )-dependent changes over large energies ( $\sim$ 10 eV) in RESPES and XAS. The observed non-integral mean valencies of $\sim$ 2.35 $\pm$ 0.03 ( $T$ = 120 K) and $\sim$ 2.70 $\pm$ 0.03 ( $T$ = 40 K) indicate homogeneous mixed valence above and below $T$ $_{v}$ . The redistribution between Eu $^{2 +}$ $4 f^{7}$ + $[s p d]^{0}$ and Eu $^{3 +}$ $4 f^{6}$ + $[s p d]^{1}$ states is attributed to a hybridization change coupled to a Kondo-like volume collapse.

4 pages, 3 figures

Temperature dependent Eu 3d-4f X-ray Absorption and Resonant Photoemission Study of the Valence Transition in EuNi2​(Si0.2​Ge0.8​)2​

Abstract

Temperature dependent Eu 3d-4f X-ray Absorption and Resonant Photoemission Study of the Valence Transition in $E u N i_{2} (S i_{0.2} G e_{0.8})_{2}$