Effect of doping and annealing on crystal structure and magnetic properties of La1–xAgxMnO3 magnetic nanoparticles

Анотація

We study crystal structure and magnetic properties of La_1–xAg_xMnO₃ nanopowders prepared by glycine — nitrate method. The particle size and crystal structure were modified by heat treatment. The average size of particle varies from about 26.6(4) nm for as prepared sample to 63.3(9) nm for annealed sample at 900 °C/2h. Crystal structure changes from orthorhombic Pnma to rhombohedral R3̅c after annealing at 600 °C/2h. The saturated magnetization μ_s and the Curie temperature T_C increase with annealing; T_C is more than doubled after annealing at 600 °C/2h. Exchange bias phenomena were first observed on nanoparticles with orthorhombic crystal structure. The hysteresis loop shifts in horizontal and vertical direction after cooling in magnetic field μ₀H_cf ≠ 0 through T_C. The values of exchange bias field μ₀H_E, coercive field μ₀H_c, remnant asymmetry μ_E and coercive magnetization μ_c increase with increasing value of cooling field μ₀H_cf. In addition the training effect was observed.