Anomalous magnetic properties of Heusler superconductor YbPd2Sn

We have investigated the magnetic properties of the Heusler compound YbPd2Sn, which exhibits coexistence of superconductivity (T-c = 2.3 K) and antiferromagnetism (T-N = 0.22 K). In the temperature dependence of the specific heat in applied magnetic fields, we found an anomalous broadening of the Schottky peak caused by the Zeeman splitting of the Gamma(7) crystalline-electric-field (CEF) ground state of the Yb3+ ions. This fact indicates the existence of antiferromagnetic (AF) short-range correlations, which are hardly destroyed by magnetic field. An anomalous temperature dependence of the upper critical field B-c2 with a maximum around 0.8 K can be explained by taking into account the pair breaking effect of Cooper pairs caused by the Yb-moment fluctuation through an exchange interaction. We propose that a weak magnetic coupling between the cubic Pd sublattice responsible for superconductivity and the NaCl-type Yb-Sn sublattice responsible for the AF magnetic ordering play an essential role for the coexistence. (C) 2000 Elsevier Science B.V. All rights reserved.