Electronic structure and magnetic interactions in LiV 2 O 4

We present results of all-electron electronic structure calculations for the recently discovered d electron heavy fermion compound LiV 2 O 4 . 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 3 d t 2 g states, which fall into two equally occupied subbands: While σ-type metal-metal bonding leads to rather broad bands, a small π-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.