Electronic structure and magnetic interactions in LiV2O4

We present results of all-electron electronic structure calculations for the recently discovered d electron heavy fermion compound LiV2O4. The augmented spherical wave calculations are based on density functional theory within the local density approximation. The electronic properties near the Fermi energy originate almost exclusively from V 3d t(2g) states, which fall into two equally occupied subbands: While sigma-type metal-metal bonding leads to rather broad bands, a small pi-type p-d overlap causes a narrow peak at E-F. Without the geometric frustration inherent in the crystal structure, spin-polarized calculations reveal an antiferromagnetic ground state and ferromagnetic order at slightly higher energy. Since direct d-d exchange interaction plays only a minor role, ordering of the localized vanadium moments can be attributed exclusively to a rather weak superexchange interaction. With the magnetic order suppressed by the geometric frustration, the remaining spin fluctuations suggest an explanation of the low-temperature behaviour of the specific heat.