New ferrimagnetic oxide CaCu ₃Cr ₂Sb ₂O ₁₂: High-pressure synthesis, structure, and magnetic properties

A new perovskite-type oxide, CaCu ₃Cr ₂Sb ₂O ₁₂, has been synthesized at 10 GPa and 1100°C. This compound crystallizes in space group Pn3 and shows simultaneous cation ordering on both A and B sites. Magnetization measurements indicate that an interaction between A-site Cu(II) and B-site Cr(III) cations dominates over possible antiferromagnetic couplings between Cu(II)-Cu(II) ions or Cr(III)-Cr(III) ions and induces net spontaneous magnetic moment below ~160 K. The lack of significant hysteresis in the isothermal magnetization curves suggests that CaCu ₃Cr ₂Sb ₂O ₁₂ is a soft ferrimagnet, which is consistent with the thermomagnetic irreversibility and magnetic susceptibility behavior. Interestingly, the experimentally determined effective magnetic moment of ∼ 1.4 μ _B at 5 K is significantly smaller than the expected value of 3 μ _B estimated assuming an antiparallel alignment of the spins of Cu(II) and Cr(III). Significant spin canting may account for the small magnetic moment. Such an anomalously small magnetization is similar to that of CuCr ₂O ₄ spinel showing a non-unidirectional spin canting behavior.