Structural and magnetic properties of LiNi 0.5 Mn 1.5 O 4 and LiNi 0.5 Mn 1.5 O 4−δ spinels: A first-principles study

Structural and magnetic properties of LiNi 0.5 Mn 1.5 O 4 and LiNi 0.5 Mn 1.5 O 4−δ are investigated using density-functional theory calculations. Results indicate that nonstoichiometric LiNi 0.5 Mn 1.5 O 4−δ and stoichiometric LiNi 0.5 Mn 1.5 O 4 exhibit two different structures, i.e., the face-centred cubic ( Fd -3 m ) and primitive, or simple, cubic ( P 4 3 32) space groups, respectively. It is found that the magnetic ground state of LiNi 0.5 Mn 1.5 O 4 ( P 4 3 32 and Fd -3 m ) is a ferrimagnetic state in which the Ni and Mn sublattices are ferromagnetically ordered along the [110] direction whereas they are antiferromagnetic with respect to each other. We demonstrate that it is the presence of an O-vacancy in LiNi 0.5 Mn 1.5 O 4−δ with the Fd -3 m space group that results in its superior electronic conductivity compared with LiNi 0.5 Mn 1.5 O 4 with the P 4 3 32 space group.