Specific features of magnetic and transport properties of La1-xM1+xO3 manganites

Magnetic and transport properties of manganites with manganese excess La1-xMn1+xO3 were studied, the results are presented. It was shown that magnetic and charge ordering depends essentially on the content of superstoichiometric manganese, magnetic field and pressure. Growth of manganese concentration gives rise to increase in magnetoresistive effect (MRE). In addition to paramagnetic-ferrimagnetic transition in samples with x = 0.1-0.4 temperature dependences of magnetization manifest anomalies at low temperatures. If at T < 45 K in the field H ≤ 0.21 kOe magnetization decreases, with H change from 0.2 to 10 kOe it increases. Analysis indicated that specific features of magnetic behavior observed at low temperatures in all probability stem from transition from ferromagnetic state to a skewed spin structure in clusters of different-valence manganese ions. The character of temperature dependences of magnetization and resistance does not change with pressure increase. Growth in manganese content and pressure results in the Curie point and metal-dielectric transition temperature displacement towards high temperatures. The temperature of MRE peak under pressure increases, whereas MRE value decreases