Structure and ferromagnetism in Mn 4+ spinels: AM 0.5Mn 1.5O 4 (A = Li, Cu; M = Ni, Mg)

The structure and electronic properties of a series of Mn IV spinel oxides, with the general formula, AM 0.5Mn 1.5O 4 (A = Li, Cu; M = Ni, Mg), are investigated. These materials form an interesting analogy to pyrochlore structures that show colossal magnetoresistance properties. Studies of all the compounds show spontaneous magnetization at a well-defined transition temperature and their semiconducting nature