Influence of Fe³⁺ substitution on crystallographic and magnetic structures of CaCu₃Ti₄O₁₂ perovskites: powder X-ray and neutron diffraction studies

Crystallographic and magnetic structures of quadruple perovskite series, CaCu_3-xFe_2xTi_4-xO₁₂ (x = 0.0, 0.1, 0.3, 0.5, and 0.7), have been meticulously examined by powder X-ray diffractometry (PXRD) and neutron diffraction at ~ 300 K. The Rietveld refinement of PXRD profiles verified monophasic formation for all the compositions. Contrarily, analysis of neutron diffraction profiles revealed a single-phase nature for x = 0.0 and 0.1 compositions while for x = 0.3, 0.5, and 0.7 compositions, formation of a secondary Magneli phase, Ti₆O₁₁. Various structural parameters in conjunction with the distribution of cations have been resolute and discussed in depth. The magnetic spin structure established an anti-ferromagnetic (x = 0.3) to ferromagnetic (x = 0.5 and 0.7) phase transition. The disparity between the experimental and calculated magnetic moment is an inkling of a spin structure to be non-collinear for x = 0.3–0.7 compositions.