Degenerate antiferromagnetic states in spinel oxide LiV 2 O 4

The magnetic and electronic properties of spinel oxide LiV2O4 have been systematically studied by using the spin-polarized first-principles electronic structure calculations. We find that a series of magnetic states, in which the ferromagnetic (FM) V4 tetrahedra are linked together through the cornersharing antiferromagnetic (AFM) V4 tetrahedra, possess degenerate energies lower than those of other spin configurations. The large number of these energetically degenerated states being the magnetic ground state gives rise to strong magnetic frustration as well as large magnetic entropy in LiV2O4. The corresponding band structure and density of states of such a typical magnetic state in this series, i.e. the ditetrahedron (DT) AFM state, demonstrate that LiV2O4 is in the vicinity of metal-insulator transition. Further analysis suggests that the t2g and eg orbitals of V atoms play different roles in the magnetic exchange interactions. Our calculations are consistent with previous experimental measurements and shed light on understanding the exotic magnetism and the heavy-fermion behavior of LiV2O4.