Structural and magnetic properties of the CaFe2 − xMnxO4 solid solution

Abstract

Substitution of Mn for Fe in the orthorhombic compound CaFe₂O₄ has been achieved by solid-state reactions at 1100 °C in air up to the composition Ca(Fe_1.6Mn_0.4)O₄. The evolution of cell and atomic parameters was determined from X-ray powder data using the Rietveld method. The results show that the presence of the Jahn–Teller ion Mn³⁺ distorts the Fe1 octahedral site and that Mn most probably occupies the Fe2 site. With increasing Mn content, the magnetism evolves from antiferromagnetic to ferrimagnetic, with Curie temperature (T_C) values (194–209 K) well above the Néel temperature of CaFe₂O₄ (160 K). A correlation between the evolution of T_C and the deviation of the Fe2–O–Fe2 angle from 90° is established.