Microscopic Observations of Electronic States in Pressure-induced Ordered Phases of Ce-, Yb-based Heavy Fermion Systems

Abstract

The recent progress of high pressure techniques, e.g. a development of nonmagnetic NiCrAl alloy, has enabled us to create pressure over 3 GPa by piston cylinder type pressure cells. Using these new techniques, the nuclear quadrupolar resonance (NQR) and ac-susceptibility (ac-χ) measurements were carried out on strongly correlated electron systems, CeRhIn₅ and YbInCu₄ under pressure. CeRhIn₅ shows pressure-induced phase transition from antiferromagnetic ordering to superconducting states. The present NQR and ac-χ studies revealed a homogeneous coexistence of these two types of orderings near the phase boundaries. Also the ac-χ and NQR investigations on YbInCu₄ showing the first-order valence transition at 42 K and at ambient pressure, indicated that ground state of this compound is a ferromagnetically ordered one after the valence transition is suppressed by pressure.