Abstract
The influence of the heat treatment on the structural and magnetic properties of the nanoparticle La 0.7Ca 0.3MnO 3 compound has been studied. The starting single-phase sample was prepared by the glycine–nitrate method without additional heating. The as-prepared specimen has been afterward annealed at two different temperatures of 600 °C and 900 °C. All three samples where characterized by XRPD, SEM and TEM, as well as by the SQUID magnetometry. Rietveld analysis of the XRPD data showed the orthorhombic perovskite structure (space group Pnma) of all the samples, while the unit cell parameters underwent a contraction with the annealing temperature. The influence of the heat treatment on the crystal structure is to decrease the orthorhombic distortion by changing the geometrical parameters. The TEM micrographs showed the increase of the mean particle size with annealing temperature from 10 nm up to 50 nm. DC magnetization and AC susceptibility measurements revealed the change of magnetic properties with the increase of the particle size: both para-to-ferromagnetic transition temperature T C and saturation magnetization M S were shifted to higher values with the simultaneous decrease of the coercivity H C. In addition, annealing procedure suppresses the spin-glass-like state that emerges in the as-prepared sample below T f = 95 K.
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