Preparation and magnetic properties of LaMnO3+δ (0≤δ≤0.154)

The structural, electrical, and magnetic properties of ceramic perovskite manganites LaMnO3+delta (delta = 0-0.154) are investigated. It is found that, in a weak magnetic field (B = 2G), the LaMnO3+delta manganite with delta = 0.065 at temperatures below the Curie temperature T-C of the paramagnet-ferromagnet phase transition has a mixed (spin glass + ferromagnet) phase. In LaMnO3+delta manganites with the parameter delta = 0.100-0.154, this phase transforms into a frustrated ferromagnetic phase. A similar transformation was observed previously in La1-xCaxMnO3 compounds at calcium contents in the range 0 <= x <= 0.3. This similarity is explained by the fact that, in both materials, the Mn4+ concentration and, accordingly, the hole concentration c change equally in the concentration range from approximate to 0.13 to 0.34 with an increase in x or delta. However, the magnetic irreversibility, the concentration dependences of the Curie temperature T-C(c) and the magnetic susceptibility chi(c), and the critical behavior of the temperature dependence of the susceptibility chi(T) in the vicinity of the Curie temperature T-C differ substantially for these two materials. The observed differences are associated with the distortion of the cubic perovskite structure, the decrease in the degree of lattice disorder, and a more uniform distribution of holes in the LaMnO3+delta manganites as compared to the La1-xCaxMnO3 compounds.