Crystal and magnetic structures of the ternary carbides Ho 2Mo 2C 3 and Er 2Mo 2C 3

Abstract

The nuclear and the magnetic structures of Ho 2Mo 2C 3 and Er 2Mo 2C 3 have been determined from neutron powder diffraction data. The magnetic properties of both compounds have also been investigated with a SQUID magnetometer. The nuclear structure of both compounds (space group C2/m, Z=2) is similar to that determined earlier for Ho 2Cr 2C 3. The only essential difference arises through the differing location of one carbon position. The magnetic moments of the holmium and erbium atoms order ferromagnetically with Curie temperatures of 13.5(5) and 8.0(5) K, respectively. Chemical bonding in Ho 2Mo 2C 3 and Er 2Mo 2C 3 is briefly discussed. In both structures the transition metal and carbon atoms form two-dimensionally infinite polyanions, which are separated from each other by the rare earth atoms. The 18-electron rule can only be obeyed for the transition metal atoms if bonding interactions between the rare earth atoms are neglected.