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

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 ( R 3 ¯ 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 ( P 1 ¯ ) 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.