Neutron scattering study of the charge ordering and the spin ordering of the magnetically frustrated spinel antiferromagnet

Neutron scattering measurements of an antiferromagnet spinel LiMn2O4 were performed using a polycrystalline sample. A bump signal peaked at 1.4 A(-1) appears below 100 K, though the line width of the magnetic diffraction pattern remains broad even at 8 K. Additionally, Mn spins freeze below 60 K. In LiMn2O4, magnetic ions, i.e., Mn3+ and Mn4+, form a network of corner-shared-tetrahedra. The observed magnetic pattern is explained by the following charge and the magnetic ordering. Two Mn3+ ions and two Mn4+ ions randomly distribute on four corners of each tetrahedron. The antiferromagnetic correlation exists only in the arrangements of Mn3+-Mn3+ and Mn4+-Mn4+ and no correlation in Mn3+-Mn4+; this is due to the frustration of spins between the arrangements of Mn3+-Mn3+ and Mn4+-Mn4+.