Magnetic properties of LaNi_(1-x)Mn_xO_(3+δ) perovskites

摘要

Magnetic measurements have been carried out in different LaNi_(1-x)Mn_xO_(3+δ) samples with 0.1 ≤ x ≤ 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 ≥ 0.5. Neutron patterns of LaNi_(0.5)Mn_(0.5)O_(3+δ) samples show an ordered arrangement of Ni and Mn atoms in the perovskite lattice. LaNi_(0.5)Mn_(0.5)O_(3+δ) is then, a double perovskite A_2BB'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 LaNi_(0.5)Mn_(0.5)O_(3+δ). The role of competitive magnetic interactions, structural disorder, magnetic anisotropy and magnetic disaccommodation is also discussed.