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Hall effect in YbXCu4and the role of carrier density in the YbInCu4valence transition

  • Author(s): Figueroa, E
  • Lawrence, JM
  • Sarrao, JL
  • Fisk, Z
  • Hundley, MF
  • Thompson, JD
  • et al.
Abstract

An unrealistically large value of the Gruneisen parameter is required to explain the valence transition which occurs at 42 K in YbInCu4as due to a Kondo Volume Collapse. A hint as to the origin of the transition lies in the large change in carrier density which occurs at the transition, from trivalent semimetallic behavior at high temperature to mixed valent metallic behavior at low temperature. In this paper we report measurements of the Hall coefficient RHfor temperatures in the range 15-300 K for a series of RXCu4compounds (R = Yb, Lu and X = Au, Zn, Cd, Mg, Tl) that form in the cubic C15b structure. For all X the Hall coefficients are small (∼10-10m3/C) so that the transport appears to be metallic. The observation that low carrier density is unique to RInCu4 leads us to hypothesize that the valence transition (which is also unique to YbInCu4) is connected with the existence of a quasigap, which is a common feature of the band structure of RXCu4. The quasigap allows for two competing hybridization states of the 4f electrons: a small TKsemimetallic state and a large TKmetallic state. © 1998 Elsevier Science Ltd. All rights reserved.

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