Composition effect in ferromagnetic properties of Tb3Co3Ga

The magnetic properties of Tb3Co3Ga, crystallizing into the orthorhombic W3CoB3-type structure, have been investigated by focusing on a composition effect. Tb3Co3Ga has been characterized as a ferromagnet by measuring the dc and ac magnetic susceptibilities and the magnetization curve. We have found that the Curie temperature determined by the ac susceptibility is highly sensitive to the atomic composition, and ranges from 90 K to 117 K. The crystal structure parameters slightly change with the Ga concentration. The lattice parameter a correlates with the coercive field; a shrinkage of a leading to an enhanced crystalline anisotropy increases the coercive field. There are two inequivalent crystallographic sites Tb1 and Tb2 for Tb atoms. The narrowing of the Tb1-Tb2-Tb1 angle would contribute to the enhanced Curie temperature, which can be qualitatively explained by considering the 4f charge distribution of Tb3+ ion.