2-STEP FERROMAGNETIC ORDERING OF CE2SI3-DELTA

The crystal structure and magnetic properties of a compound of nominal composition CeSi1.33 were investigated by means of neutron diffraction and magnetic measurements. The crystal structure of this compound was found to be isotypic with the orthorhombic Nd2Si3-delta structure with two formula units per unit cell, comprising two Ce sites and three Si sites. Refinement showed that one of the Si positions is only 70% occupied, leading to the formula composition Ce2Si3-delta With delta=0.30. The compound orders ferromagnetically at about 35 K with the Ce moments oriented along the c direction. A strong difference in the magnitude of the Ce moments between the two sites was observed (1.72 and 0.43 mu(B) per Ce), while the temperature dependences of the two corresponding sublattice moments are also different.