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

Abstract

The compounds CeGa₂, Ce_0.82Mg_0.50Ga_1.68, Eu(Mg/Li)_xGa_2-x (0≤x≤0.4) and Eu(Mg/Li)_xGa_4-x (0 ≤x≤0.73) were synthesized and characterized by X-ray diffraction. CeGa₂ and Ce_0.82Mg_0.50Ga_1.68 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 [001] direction and the Ce atoms are sandwiched between them. Eu(Mg/Li)_xGa_2-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 [100] plane forming a puckered network with voids occupied by two Eu atoms. The Eu(Mg/Li)_xGa_4-x (0 ≤x≤0.73) compounds crystallize in the BaAl₄ structure type having I4/mmm space group. In Eu(Mg/Li)_xGa_4-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.