Observation of antiferromagnetism in marokite CaMn2O4

Marokite (CaMn2O4) has been identified as a low-level impurity in the solid-state synthesis of Ca1-xLaxMnO3 perovskites in the low-x region. In order to properly isolate the complex magnetic behavior of these important perovskites, the low-temperature magnetic structure and properties of marokite are determined and reported. All Mn ions are in the high-spin 3 + oxidation state. Jahn-Teller-distorted NIMO, octahedra share both edges and vertices in a three-dimensional network, through which various exchange mechanisms cooperatively give rise to antiferromagnetic Mn3+ spin order. The magnetic order is evidenced below T-N = 220 K by a peak in the magnetic susceptibility and the appearance of symmetry-lowering magnetic Bragg reflections in neutron diffraction. (C) 2001 Academic Press.