SPIN FLUCTUATIONS IN THE HEAVY-FERMION PARAMAGNETIC U(IN0.5SN0.5)3

Sn-119 Mossbauer spectra of the heavy-fermion intermetallic system U(In0.5Sn0.5)3 have been measured in the temperature range 4.2-300 K. The room temperature spectrum is characterized by a quadrupole doublet with a splitting value of 1.45 mm/s. With decreasing temperature the spectral line width increases and a hyperfine magnetic structure is developed at helium temperatures. This hyperfine field may be interpreted as being transferred via the conduction-electron polarization from the U to the Sn nucleus. A detailed analysis of the spectral evolution with temperature proves the presence of spin fluctuations in U(In0.5Sn0.5)3 near the transition from local-moment magnetism to itinerant f-electron behavior. The temperature dependence of the spin relaxation rate has been determined.