Magnetic and magnetotransport properties of La1−xBaxMnO3−x/2 perovskite manganites
Abstract
Crystal structure as well as magnetization and electrical transport vs. temperature and field for the La3+1−xBa2+xMn3+O2−3−x/2 (0 ≤ x ≤ 0.50) anion-deficient manganites have been studied. It is established that the samples in the region 0 ≤ x ≤ 0.05 are O/-orthorhombic perovskites and are rhombohedric with 0.10 ≤ x ≤ 0.25, whereas with 0.27 ≤ x ≤ 0.50 they are cubic. As the doping level increases the samples undergo a transition from a weak ferromagnetic (x = 0) to an inhomogeneous ferromagnetic (x ≥ 0.03) state. At x ≥ 0.12 samples show cluster spin glass properties with the temperature of magnetic moment freezing ∼45 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 La3+1−xBa2+xMn3+O2−3−x/2 manganites have been established by magnetic measurements and compared with those for stoichiometric ones. Magnetic data for the reduced La3+1−xBa2+xMn3+O2−3−x/2 manganites have been compared with those for the stoichiometric La3+1−xBa2+xMn3+1−xMn4+xO2−3. The magnetic state of the anion-deficient samples is interpreted on the basis of the superexchange interaction model.