MAGNETIC PHASE TRANSFORMATIONS IN Sb-SUBSTITUTED RARE-EARTH MANGANITES BASED ON Mn3+ IONS

Abstract

Neutron diffraction, magnetic and magnetotransport studies of perovskites La_1–x Sr_x ( Mn³⁺_1-x/2 Sb⁵⁺_x/2)O₃ (x ≤ 0,7) containing only Mn3+ ions were carried out. It is shown that at x ~ 0.2, the system goes from the antiferromagnetic state to the ferromagnetic one. In this case, the structure is transformed from the O′-orthorhombic structure to the O-orthorhombic one, which is due to orbital disordering. At x ≥ 0.6, the cluster spin glass phase arises due to the competition between antiferromagnetic and ferromagnetic interactions, as well as due to strong diamagnetic dilution. As the ionic radius of the rare-earth ion is decreased in the series R_0,7Sr_0,3Mn_0,85Sb_0,15O₃, the ferromagnetic state is gradually transformed into spin glass (R = Sm). All ferromagnetic compounds are insulators with a large magnitude of the magnetoresistive effect. The high covalence and orbital disordering are assumed to be responsible for ferromagnetism in the compounds under study.