Hyperfine-enhanced nuclear magnetism in Pr-based compounds observed by muon spin relaxation

Ito, Takashi   ; Higemoto, Wataru  ; Oishi, Kazuki; Nishida, Nobuhiko*; Karaki, Yoshitomo*; Ishimoto, Hidehiko*

Several novel phenomena about higher order multipoles have recently been found in Pr-based compounds with a nonmagnetic crystalline-electric-field (CEF) ground state. Previous SR studies in such compounds reported an anomalous muon spin relaxation at low temperatures in spite of the CEF ground state with the nonmagnetic nature, and a hyperfine-enhanced nuclear magnetism was discussed as the origin. A Van-Vleck paramagnet PrPt is a typical system of the enhanced nuclear magnetism, which exhibits a ferromagnetic nuclear ordering at =1.7 mK. This compound has been well characterized and is an ideal system to clarify a relation between the enhanced nuclear magnetism and the anomalous muon spin relaxation in Pr-based compounds. We performed SR measurements down to 50 mK. An internal field observed at the muon site is much larger in magnitude than ones due to bare nuclear dipole moments, suggesting an induction of 4 magnetic moments. A fluctuation rate of the field was estimated in the order of a few MHz and the value for is consistent with one estimated from . Our observations demonstrate that the SR is an ideal tool to investigate the dynamics of the hyperfine-enhanced nuclear spins in electron systems.