Structural and magnetic studies on RInPt₄ (RLaTm) compounds

The compounds RInPt₄, with RLaTm, have been synthesized for the first time and to crystallize in the cubic MgSnCu₄ type structure for RLaDy. However, TmInPt₄ appears to stabilize in the Cu₃Au type structure while X-ray patterns of ErInPt₄ and HoInPt₄ contain lines belonging to both these structure types. In this series, only the unit cell volume of EuInPt₄ does not follow the usual lanthanide contraction, indicating the nontrivalent nature of Eu ion in this compound. Magnetic susceptibility of these compounds has been measured in the temperature range from 4.2 to 300 K. All the compounds, except EuInPt₄ and GdInPt₄, remain paramagnetic down to 4.2 K. The compounds EuInPt₄ and GdInPt₄ order ferromagnetically with Curie temperature, T_M, of 53 and 20 K respectively. The susceptibility of CeInPt₄ shows considerable deviation from Curie-Weiss behaviour below 100 K similar to that observed in heavy fermion compounds. The paramagnetic Curie temperature (θs_p) changes sign from negative to positive with increasing atomic number of the rate earth ion in this series.