Unraveling the nature of Fe-doping mediated inter- and intra-chain interactions in Ca3Co2O6

The structural and magnetic properties of quasi-one-dimensional (1D) spin-chain compounds Ca3Co2-xFexO6 (x = 0, 0.1, 0.2 and 0.3) synthesized by a sol-gel method have been systematically studied by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), neutron powder diffraction (NPD), dc and ac magnetization measurements. The samples adopt a rhombohedral crystal structure with the space group R-3c in a temperature range of 5–100 K. Fe ions are found to locate at the trigonal prism Co2 crystallographic sites. Fe doping converts some of low-spin Co3+ ions at Co1 octahedral sites into Co2+ ions. For the high-temperature paramagnetic phase, the Curie paramagnetic temperature θp changes its sign from positive to negative at x = 0.2, implying that the dominant magnetic interaction is driven from ferromagnetic (FM) to antiferromagnetic (AFM) upon Fe substitution. A partial low-spin to high-spin state crossover of the Co1 ions is observed at high Fe-doping level x = 0.3. All the samples exhibit a long-range spin-density wave (SDW) AFM ordering below TN, followed by a spin-glass-like transition at Tf. These low-temperature magnetic phases were significantly suppressed upon Fe doping. The Fe substitution in Ca3Co2-xFexO6 weakened both intrachain and interchain magnetic interactions, caused by enhanced magnetic disorder due to the different magnetic characters of Ising Co and Heisenberg Fe spins. •Fe ions prefer to locate at the Co2 trigonal prism crystallographic sites.•Fe doping converts some of low-spin Co3+ ions at octahedral sites into Co2+ ions.•Partial low-spin to high-spin state transition for Co3+/Co2+ at octahedral sites.•Complex inhomogeneous magnetic state with coexistence of a long-range AFM order and glass-like magnetic phase.•Suppression of both the magnetic phases upon Fe substitution.