Muon spin relaxation and nonmagnetic Kondo state in PrInAg2

Muon spin relaxation experiments have been carried out in the Kondo compound PrInAg2. The zero-field muon relaxation rate is found to be independent of temperature between 0.1 and 10 K, which rules out a magnetic origin (spin freezing or a conventional Kondo effect) for the previously observed specific-heat anomaly at ∼0.5 K. At low temperatures the muon relaxation can be quantitatively understood in terms of the muon’s interaction with nuclear magnetism, including hyperfine enhancement of the 141Pr nuclear moment at low temperatures. This argues against a Pr3+ ground-state electronic magnetic moment, and is strong evidence for the doublet Γ3 crystalline-electric-field-split ground state required for a nonmagnetic route to heavy-electron behavior. The data imply the existence of an exchange interaction between neighboring Pr3+ ions of the order of 0.2 K in temperature units, which should be taken into account in a complete theory of a nonmagnetic Kondo effect in PrInAg2.