Magnetic and magnetotransport properties of La1-xBaxMnO3-x/2 perovskite manganites

Crystal structure as well as magnetization and electrical transport vs. temperature and field for the La1-x3+Bax2+Mn3+O3-x/22- (0less than or equal toxless than or equal to0.50) anion-deficient manganites have been studied. It is established that the samples in the region 0less than or equal toxless than or equal to0.05 are O'-orthorhombic perovskites and are rhombohedric with 0.10less than or equal toxless than or equal to0.25, whereas with 0.27less than or equal toxless than or equal to0.50 they are cubic. As the doping level increases the samples undergo a transition from a weak ferromagnetic (x=0) to an inhomogeneous ferromagnetic (xgreater than or equal to0.03) state. At xgreater than or equal to0.12 samples show cluster spin glass properties with the temperature of magnetic moment freezing similar to45 K. All the reduced samples are semiconductors and show considerable magnetoresistance over a wide temperature range. The largest magnetoresistance ratio is observed for the x=0.30 sample. Concentration dependences of spontaneous magnetization and the magnetic ordering temperature for the reduced La1-x3+Bax2+Mn3+O3-x/22- manganites have been established by magnetic measurements and compared with those for stoichiometric ones. Magnetic data for the reduced La1-x3+Bax2+Mn3+O3-x/22- manganites have been compared with those for the stoichiometric La(1-x)(3+)Bax(2+)Mn(1-x)(3+)Mn(x)(4+)O(3)(2-). The magnetic state of the anion-deficient samples is interpreted on the basis of the superexchange interaction model.