Muon spin relaxation and hyperfine-enhanced Pr nuclear spin dynamics in Pr(Os,Ru)Sb and (Pr,La)OsSb

Shu, L.*; MacLaughlin, D. E.*; Aoki, Yuji*; Tsunashima, Yoshino*; Yonezawa, Yuki*; Sanada, Shotaro*; Kikuchi, Daisuke*; Sato, Hideyuki*; Heffner, R. H.; Higemoto, Wataru  ; Oishi, Kazuki; Ito, Takashi   ; Bernal, O. O.*; Hillier, A. D.*; Kadono, Ryosuke*; Koda, Akihiro*; Ishida, Kenji*; Sugawara, Hitoshi*; Frederick, N. A.*; Yuhasz, W. M.*; Sayles, T. A.*; Yanagisawa, Tatsuya*; Maple, M. B.*

Zero- and longitudinal-field muon spin relaxation experiments have been carried out in the alloy series Pr(OsRu)Sb and PrLaOsSb to elucidate the anomalous dynamic muon spin relaxation observed in these materials. The damping rate associated with this relaxation varies with temperature, applied magnetic field, and dopant concentrations and in a manner consistent with the "hyperfine enhancement" of Pr nuclear spins. This mechanism arises from Van Vleck-like admixture of magnetic Pr crystalline-electric-field-split excited states into the nonmagnetic singlet ground state by the nuclear hyperfine coupling, thereby increasing the strengths of spin-spin interactions between Pr and muon spins and within the Pr spin system. We find qualitative agreement with this scenario and conclude that electronic spin fluctuations are not directly involved in the dynamic muon spin relaxation.