NMR and NQR Studies of Rare-Earth Compound YbInCu₄ under High Pressure

Abstract

The NQR technique was applied to investigate the valence phase transition of YbInCu₄ under high pressures. The Cu NQR frequency ν_Q increases with increasing pressure in both of low and high temperature phases. The transition temperature T_v decreases with increasing pressure at a rate of -2.2 K/kbar. The nuclear spin-lattice relaxation rate T₁^-1 shows no temperature and pressure dependence in the high temperature phase, suggesting the localized 4f state of Yb³⁺ ion. In the low temperature phase, (T₁T)^-1 are constant at various pressures and show a Korringa like behavior.