Magnetic properties of Er(Co, Mn)O_3 perovskites

摘要

The erbium-based manganite ErMnO_3 has been partially substituted at the manganese site by Co in the general formula ErCo_xMn_(1-x)O_3. The perovskite orthorhombic structure is found fromx(Co) = 0.3 up to x(Co) = 0.7, provided that the synthesis is performed under oxygenation conditions to favour the presence of Co~(3+). Magnetic properties show unusual phenomena, correlated with the presence of different magnetic entities (i.e., Er~(3+), Co~(2+), Co~(3+), Mn~(3+), Mn~(4+)): the overall magnetic moment reverses its sign when the sample is cooled under an external magnetic field, while the magnetization loops performed at T<4K show intersecting branches at low fields and a sudden jump at high fields. A phenomenological model of two interacting sublattices, coupled by an antiferromagnetic exchange interaction, explains the inversion of the overall spin, while the high-field discontinuity is explained in terms of dynamical models.