Relation between the magnetic properties and the crystal and electronic structures of manganese spinels LiNi0.5Mn1.5O4 and LiCu0.5Mn1.5O4−δ (<δ<0.125)

The magnetic properties of LiM0.5Mn1.5O4 (M=Ni and Cu) spinels, materials of interest as electrodes for Li-ion batteries, have been studied and interpreted with the help of the first-principles calculation method. The magnetic susceptibility of the Ni compound, that behaves virtually as stoichiometric normal spinel, is consistent with the well-established magnetic model of the spinel structure that leads to ferrimagnetism. However, the Cu spinel was oxygen deficient and showed significant divergences from this model. The ferromagnetic component of this spinel was dependent on the calcining temperature and was smaller to that predicted by the magnetic model. The special crystal structure of the spinel, namely, oxygen deficiency and increased occupancy of the tetrahedral sites by Cu ions, satisfactorily explains the more complex magnetic behavior observed, further supported by the results of the first-principles electronic structure computations.