Magnetic properties of LaNi1-xMnxO3+δ perovskites

Magnetic measurements have been carried out in different LaNi1-xMnxO3+delta samples with 0.1 less than or equal to x less than or equal to 0.9. All these samples show two magnetic anomalies, one at relatively high temperature characteristic of a ferromagnetic ordering and the other at low temperature, typical of magnetic relaxation phenomena. Neutron diffraction patterns indicate that long-range ferromagnetic ordering is only achieved for x greater than or equal to 0.5. Neutron patterns of LaNi0.5Mn0.5O3+delta samples show an ordered arrangement of Ni and Mn atoms in the perovskite lattice. LaNi0.5Mn0.5O3+delta is then, a double perovskite A(2)BB'O-6 whereas Ni and Mn atoms are randomly distributed for the rest of the samples. X-ray magnetic circular dichroism experiments confirm the presence of collinear ferromagnetism in LaNi0.5Mn0.5O3+delta. The role of competitive magnetic interactions, structural disorder, magnetic anisotropy and magnetic disaccommodation is also discussed.