Mössbauer and Magnetic Studies of Doped Lanthanum Manganite La1 – xCaxMn0.98Fe0.02O3 (x = 0.05, 0.10, 0.20): II. Stoichiometric Composition and Phase Segregation

Resumo

Phase segregation in calcium-doped lanthanum manganite of stoichiometric composition La_1 – xCa_xMn_0.98Fe_0.02O₃ (x = 0.05, 0.10, 0.20) is studied in a wide temperature range by Mössbauer spectroscopy, X-ray diffraction analysis, and magnetic methods. Structural phase segregation is the coexistence of three rhombic phases, I, II, and II*, described by the same space group Pnma and characterized by different types of magnetic ordering at low temperatures. Phase I transitions to the ferromagnetic state as the temperature decreases, and phases II and II* become antiferromagnetic. At 80 K, stoichiometric samples demonstrate a relaxation behavior which can be due to the presence of small-sized magnetic clusters. The relative content of the ferromagnetic phase increases with increasing Ca content, and the temperature of its magnetic transition grows.