Charge and spin ordering inLiMn2O4

Abstract

X-ray diffraction, neutron diffraction, and susceptibility measurements were performed on ${}^7{\mathrm{LiMn}}_2{\mathrm{O}}_4$ powder specimen. The Jahn-Teller lattice distortion induces a phase transition from cubic to orthorhombic structure at $T=283.5\mathrm{}\mathrm{K}$ on cooling. A series of well-defined magnetic Bragg peaks appears below $T_N=65\mathrm{}\mathrm{K}.$ A complete charge ordering of ${\mathrm{Mn}}^{3+}$ and ${\mathrm{Mn}}^{4+}$ ions in the superlattice structure promotes the antiferromagnetic long-range order. The absence of a magnetic diffuse peak indicates that a magnetic frustration is removed from ${\mathrm{LiMn}}_2{\mathrm{O}}_4$ at low temperatures. The dynamics of the lithium ions are also discussed on the basis of the Debye-Waller factor.