Sn-119 Mossbauer study of the non-magnetic stannides UM2Sn with M = Co, Ni, Rh and Pd

Sn-119 Mossbauer study has been carried out on UCo2Sn, UNi2Sn, URh2Sn and U Pd2Sn crystallizing in an orthorhombic superstructure deriving from the cub ic Heusler lattice. At 293 K, all spectra are characterized by a quadrupole doublet. For UNi2Sn, showing a transition cubic --> orthorhombic with a la rge hysteresis from 330 to 60 K, a significant increase of the quadrupole s plitting appears with decreasing temperature; Contrary to what is observed for URh2Sn, a broadening of the quadrupole doublet of the non-magnetic stan nide UPd2Sn occurs below 20 K. This behaviour is interpreted as due to the presence of local spin correlations which induce a fluctuating hyperfine fi eld, and the thermal variation of the spin fluctuation rate is determined. (C) 1999 Elsevier Science B.V. All rights reserved.