Canted structures in the Mn3+/Mn4+ perovskites

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Abstract
Neutron diffraction and magnetization measurements have been performed on numerous systems with the divalent and monovalent substitution, Pr1−xAx2+Mn1−x3+Mnx4+O3 (A=Ca, Sr, Ba) and Pr1−x/2Ax/2+Mn1−x3+Mnx4+O3 (A=Na, K). The study shows that the transition from the Ay-type (layer) antiferromagnetism in pure PrMnO3 to the ferromagnetism in the mixed-valence systems is not continuous. In a range of about 5%–15% of Mn4+ (x∼0.05–0.15), canted magnetic arrangements of the AyFz type are observed. The interlayer coupling is changed gradually from θ=180° for x=0–0.05 to θ∼90° for x=0.15. For about x=0.15–0.20, the canted phase with 90° coupling coexists with a purely ferromagnetic arrangement of the Fy type. The observed behavior is related to an interplay of the magnetic superexchange and the double exchange.