Pressure and magnetic field effects on the volume anomaly associated with first-order valence change in YbInCu4

The effect of pressure and magnetic field on the first-order Yb valence change (from v approximate to 3 to v approximate to 2.9) at T-v approximate to 40K in YbInCu4 has been studied by measuring the change in volume associated with this transition. Volume thermal expansion measurements indicate that by applying pressure the transition is shifted to lower temperatures at the rate -2.2Kkbar(-1). From the volume anomaly at T-v, the valence change (approximate to 0.1 at ambient pressure) is found to decrease at the rate triangle v approximate to 0.0045kbar(-1). The compressibility has also been measured above and below T-v, being 0.99Mbar(-1) at T = 295K and 1.20Mbar(-1) at T = 20K. The critical magnetic field, at which Yb valence exhibits a first-order field-dependent valence change below T-v, increases with decreasing temperature. Copyright (C) 1996 Elsevier Science Ltd