119Sn Mossbauer Spectroscopy in the heavy - fermion ferrimagnet UCu5Sn

Sn-119 MOssbauer studies of UCu5Sn compound have been performed in a wide temperature range between 4.2 K and 78 K. Magnetic hyperfine split spectra observed below 1=54 K indicate the onset of magnetic ordering. The temperature dependence of the average transferred effective magnetic hyperfine field <H-eff> at the tin site can be surprisingly well fitted using the Brillouin function for S = 1/2. A rather small distribution of magnetic hyperfine fields delta(H) obtained from the fitting procedure is in favour with the assumption that atomic mixing between Cu and Sn position can be neglected. The value of theta = 10(2)degrees shows that the direction of the effective magnetic hyperfine field H-eff is close to the c-axis being in accord with the uranium magnetic moment direction.