Cubic structure and canted antiferromagnetism of CaMn7O12 doped with trivalent cations (Fe, Al, Cr)

• Dramatic effect of Fe3+, Al3+ and Cr3+ doping on structural and magnetism in CaMn7O12.
• Mn3+ and Mn4+ charge ordering of rhombohedral (R-3) CaMn7O12 is destroyed by doping.
• The doped oxides CaMn7−xMxO12 become cubic with small doping level (x=0.2 for Fe).
• TN~90 K of CaMn7O12 disappears and canted AFM established below 50–70 K in cubic phases.
• CaMn6FeO12 exhibits a spin glass like behaviour.

In this study, we show the dramatic effect of the doping of the octahedral sites with M3+ cations (Fe3+, Al3+ and Cr3+) upon the structure and magnetism of the rhombohedral double perovskite CaMn7O12. In the oxides CaMn7−xMxO12, charge ordering between Mn3+ and Mn4+ octahedral sites is destroyed leading to the cubic structure (Im-3), whereas the initial magnetic properties (TN~90 K) have disappeared leading to canted antiferromagnetism (TN≈50–70 K) for small x values (x ~0.2–1). A spin glass like behaviour is also observed for larger values (x~1) in the case of Fe substitution.