First-principles electronic structure of spinelLiCr2O4:A possible half-metal

Abstract

We have employed first-principles electronic structure calculations to examine the hypothetical (but plausible) oxide spinel, ${\mathrm{LiCr}}_{2}{\mathrm{O}}_{4}$ with the ${d}^{2.5}$ electronic configuration. The cell (cubic) and internal (oxygen position) structural parameters have been obtained for this compound through structural relaxation in the first-principles framework. Within the one-electron band picture, we find that ${\mathrm{LiCr}}_{2}{\mathrm{O}}_{4}$ is magnetic, and a candidate half-metal. The electronic structure is substantially different from the closely related and well-known rutile half-metal ${\mathrm{CrO}}_{2}.$ In particular, we find a smaller conduction-band width in the spinel compound, perhaps as a result of the distinct topology of the spinel crystal structure, and the reduced oxidation state. The magnetism and half-metallicity of ${\mathrm{LiCr}}_{2}{\mathrm{O}}_{4}$ has been mapped in the parameter space of its cubic crystal structure. Comparisons with superconducting ${\mathrm{LiTi}}_{2}{\mathrm{O}}_{4}{(d}^{0.5}),$ heavy-fermion ${\mathrm{LiV}}_{2}{\mathrm{O}}_{4}{(d}^{1.5}),$ and charge-ordering ${\mathrm{LiMn}}_{2}{\mathrm{O}}_{4}{(d}^{3.5})$ suggest the effectiveness of a nearly rigid band picture involving simple shifts of the position of ${E}_{\mathrm{F}}$ in these very different materials. Comparisons are also made with the electronic structure of ${\mathrm{ZnV}}_{2}{\mathrm{O}}_{4}{(d}^{2}),$ a correlated insulator that undergoes a structural and antiferromagnetic phase transition.