ANOMALOUS THERMODYNAMIC, TRANSPORT AND MOSSBAUER PROPERTIES OF UNISN - A HALF-METALLIC SYSTEM

Of the ternary actinide compounds UTX where T is a transition metal and X is a group III, IV or V element, UNiSn is one of the more interesting, displaying anomalous behavior in the resistivity in the form of a pronounced maximum. In this paper, we present precision measurements of the electrical resistivity, low-field magnetization and specific heat which indicate that the system is paramagnetic at high temperatures and undergoes a second-order transition to a magnetically ordered state at 43 K. Sn-119 Mossbauer spectroscopy shows that the hyperfine field seen at the Sn sites does not decrease to zero as T = 43 K is approached from below but continues to be detectable to temperatures approaching 55 K suggesting that the magnetic correlations persist well above the transition temperature. However, the percentage of Sn nuclei that see the hyperfine field decreases dramatically at 43 K. This data is consistent with recent neutron-scattering data that indicate that the system orders antiferromagnetically.