Physical properties of La1−xPbxMnO3 perovskites with 0.24 ≤ x ≤ 0.40

Abstract The La 1− x Pb x MnO 3 perovskites with 0.24 ≤  x  ≤ 0.40 crystallize in a rhombohedral structure having R 3 ¯ c space group. The temperature dependences of the lattice parameters for samples with x  = 0.24 and 0.40 evidenced no structural phase transitions between 10 and 295 K. The saturation magnetizations, at 4.2 K, increase as the Pb content is higher. A gradual transition from spin glass to ferromagnetic ordering was shown as the Pb content increases. Paramagnetic measurements and X-ray photoelectron spectroscopy studies evidenced that the relative content of Mn 4+ ions is close to that of Pb 2+ ions. The resistivities increase with temperature and a metallic to semiconducting transition is shown at temperatures smaller than the Curie points. The field and temperature dependences of the magnetoresistivities were analysed.