Effect of Li and Mg substitution on the crystal structure and magnetism of the REGa2 (REÂ =Â Ce and Eu) and EuGa4 compounds

The compounds CeGa2, Ce0.82Mg0.50Ga1.68, Eu(Mg/Li)xGa2−x (0 ⩽ x ⩽ 0.4) and Eu(Mg/Li)xGa4−x (0 ⩽ x ⩽ 0.73) were synthesized and characterized by X-ray diffraction. CeGa2 and Ce0.82Mg0.50Ga1.68 crystallize in the AlB2 structure type with P6/mmm space group. The structure is composed of infinite arrays of planar hexagonal Ga atoms stacked along the [0 0 1] direction and the Ce atoms are sandwiched between them. Eu(Mg/Li)xGa2−x (0 ⩽ x ⩽ 0.4) crystallize in the KHg2 structure type with Imma space group and consists of the hexagonal rings of M (Li/Mg + Ga) atoms connected along the [1 0 0] plane forming a puckered network with voids occupied by two Eu atoms. The Eu(Mg/Li)xGa4−x (0 ⩽ x ⩽ 0.73) compounds crystallize in the BaAl4 structure type having I4/mmm space group. In Eu(Mg/Li)xGa4−x, the Eu atom occupies the edge and the body centered position of the unit cell while the Ga and M (Li/Mg + Ga) atoms forms a 3D polyanionic framework. Magnetic susceptibility of CeGa2, EuGa2, EuGa4 and their corresponding Li/Mg analogs are discussed.