Electronic States and Possible Origin of the Orbital-Glass State in a Nearly Metallic Spinel Cobalt Vanadate: An X-ray Magnetic Circular Dichroism Study

TL;DR

This study investigates the orbital states in nearly metallic spinel cobalt vanadate using X-ray spectroscopy, revealing insights into the orbital-glass state and the magnetic moments of Co and V ions.

Contribution

It provides new understanding of the orbital and magnetic states in CoV2O4 through spectroscopic analysis and modeling, highlighting the role of excess Co ions.

Findings

Co ions are in a low-spin trivalent state with parallel magnetic moments.

V ions have a small but finite orbital magnetic moment.

Excess Co ions induce a random potential affecting the V sublattice.

Abstract

We have investigated the orbital states of the orbital-glassy (short-range orbital ordered) spinel vanadate Co$_{1.21}$V$_{1.79}$O$_{4}$ using x-ray absorption spectroscopy (XAS), x-ray magnetic circular dichroism (XMCD), and subsequent configuration-interaction cluster-model calculation. From the sign of the XMCD spectra, it was found that the spin magnetic moment of the Co ion is aligned parallel to the applied magnetic field and that of the V ion anti-parallel to it, consistent with neutron scattering studies. It was revealed that the excess Co ions at the octahedral site take the trivalent low-spin state, and induce a random potential to the V sublattice. The orbital magnetic moment of the V ion is small although finite, suggesting that the ordered orbitals mainly consists of real-number orbitals.