Characterization and electronic structure calculations of the antiferromagnetic insulatorCa3FeRhO6 (original) (raw)

Crystal structure, magnetic properties and ESR spectra of Ca3Co2−xFexO6

Journal of Alloys and Compounds, 2012

ABSTRACT We have synthesized compounds of Ca3Co2−xFexO6 (x = 0–1.5) by sol–gel reaction method. X-ray diffraction data show that the solubility limit of Fe in the spin-chain compound Ca3Co2O6 is about x = 0.7. For the rhombohedral (R3¯c) samples with x ≤ 0.7, the upward deviation from the paramagnetic Curie–Weiss law in the inverse magnetic susceptibility (H/M) tends to be suppressed at x = 0.7. Correlatively, the paramagnetic Curie temperature θP approaches zero at this concentration. The M(H) curves exhibit a well-defined ferrimagnetic state, which becomes smeared out with increasing Fe concentration and nearly disappears at x = 0.7. For the triclinic (P1¯) samples with x = 1.1, the magnetization is much small and its ground state is antiferromagnetic. The H/M curve measured up to 300 K does not follow the Curie–Weiss law. Finally, ESR spectra composed of eight hyperfine splittings due to Co nuclear spin are observed for x = 0.4.

First-principles investigation of exchange interactions in quasi-one-dimensional antiferromagnet CaV2O4

Journal of physics. Condensed matter : an Institute of Physics journal, 2015

The effects of orbital degrees of freedom on the exchange interactions in a quasi-one-dimensional spin-1 antiferromagnet CaV2O4 are systematically studied. For this purpose a realistic low-energy electron model with the parameters derived from the first-principles calculations is constructed in the Wannier basis for the t2g bands. The exchange interactions are calculated using both the theory of infinitesimal spin rotations near the mean-field ground state and the superexchange model, which provide a consistent description. The obtained behaviour of exchange interactions differs substantially from the previously proposed phenomenological picture based on magnetic measurements and structural considerations, namely: (i) despite the quasi-one-dimensional character of the crystal structure, consisting of the zigzag chains of the edge-sharing VO6 octahedra, the electronic structure is essentially three-dimensional, that leads to finite interactions between the chains; (ii) the exchange i...