Structure and magnetic properties of TbFe6-xGa6+x compounds

The TbFe6-xGa6+x compounds (x=0, 0.5, 1.0 and 1.45) have been prepared and studied by X-ray powder diffraction and magnetization measurements. The structure of the compound TbFe6-xGa6+x transfers from the orthorhombic ScFe6Ga6-type structure (space group Immm) (x=0 and 0.5) to the tetragonal ThMn12-type structure (space group I4/mmm) (x=1.0 and 1.5) and the volume of the unit cell increases as Ga content increases. The lattice parameters are a=0.85551, b=0.8626 and c=0.50717 nm for TbFe6Ga6, and a=0.86938 and c=0.50918 nm for TbFe4.55Ga7.45. The magnetization measurements indicate all the TbFe6-xGa6+x compounds have magnetic ordering. The Curie temperatures decrease from 492 K for TbFe6Ga6 to 327 K for TbFe4.55Ga7.45. The magnetization of the TbFe6-xGa6+x decreases with temperature decreases below its magnetic ordering temperature due to the increasing Tb-sublattice magnetization which is antiparallel to the Fe-sublattice magnetization.