Electronic structure of the kagome staircase compounds Ni${}_{3}$V${}_{2}$O${}_{8}$ and Co${}_{3}$V${}_{2}$O${}_{8}$

Electronic structure of the kagome staircase compounds Ni $_{3}$ V $_{2}$ O $_{8}$ and Co $_{3}$ V $_{2}$ O $_{8}$

J. Laverock, B. Chen, A. R. H. Preston, K. E. Smith, N. R. Wilson, G. Balakrishnan, P.-A. Glans, and J.-H. Guo

Phys. Rev. B 87, 125133 – Published 21 March 2013

Abstract

The electronic structure of the kagome staircase compounds, Ni $_{3}$ V $_{2}$ O $_{8}$ and Co $_{3}$ V $_{2}$ O $_{8}$ , has been investigated using soft x-ray absorption, soft x-ray emission, and resonant inelastic x-ray scattering. Comparison between the two compounds, and with first-principles band structure calculations and crystal-field multiplet models, provides unique insight into the electronic structure of the two materials. Whereas the location of the narrow (Ni,Co) $d$ bands is predicted to be close to $E_{F}$ , we experimentally find they lie deeper in the occupied O $2 p$ and unoccupied V $3 d$ manifolds, and determine their energy via measured charge-transfer excitations. Additionally, we find evidence for a $d d$ excitation at 1.5 eV in Ni $_{3}$ V $_{2}$ O $_{8}$ , suggesting the V $d$ states may be weakly occupied in this compound, contrary to Co $_{3}$ V $_{2}$ O $_{8}$ . Good agreement is found between the crystal-field $d d$ excitations observed in the experiment and those predicted by atomic multiplet theory.