High-field properties of the heavy-fermion system YbCu5 and related intermetallics

Physical properties of the heavy-fermion system YbCu5 and the YbCu5-xAgx co mpounds are studied in high magnetic fields. These systems show metamagneti c-like behavior at low temperature. This can be qualitatively explained by the Bethe-ansatz solution of the Coqblin-Schrieffer model. A large negative magnetostriction is observed in YbCu5 at low temperature, which indicates a valence change of Yb by field: from the valence-fluctuating state with it inerant 4f-electrons at low field to a stable Yb3+ state with localized mag netic moments at high field. (C) 2001 Elsevier Science B.V. All rights rese rved.