Structural and magnetic properties of spin chain compoundsCa3Co2−xFexO6

Abstract

We report the structural and magnetic properties of quasi-one-dimensional (1D) spin chain compounds ${\mathrm{Ca}}_{3}{\mathrm{Co}}_{2\ensuremath{-}x}{\mathrm{Fe}}_{x}{\mathrm{O}}_{6}$ ($x=0$, 0.1, 0.2, and 0.4). Simultaneous Rietveld refinement of powder neutron and x-ray diffraction patterns at room temperature confirmed the single-phase formation for all the samples in the rhombohedral structure with space group $R\overline{3}c$. Rietveld refinement and M\ossbauer study confirmed that ${\mathrm{Fe}}^{3+}$ ion was doped at trigonal prism site, $6a$ (0, 0, $1∕4$) of Co. Decrease of intrachain positive exchange constant $J$ and increase of interchain negative exchange constant ${J}^{\ensuremath{'}}$ with iron substitution result in deviation from ``1D character'' in these spin chain compounds. Deviation from the ${H}^{\ensuremath{-}3∕2}$ dependence of magnetization-approach to its saturation value for higher iron concentration $(x=0.4)$ further supports this observation. The observed results have been ascribed to a breaking of the ferromagnetically ordered linear spin chains along the crystallographic $c$ axis with iron doping and strengthening of antiferromagnetic exchange interaction between ${\mathrm{Fe}}^{3+}$ ions.