Effect of the degree of doping on the size and magnetic properties of nanocrystals La1 – xZnxFeO3 synthesized by the sol–gel method

Resumo

Nanopowders La_1–xZn_xFeO₃ (nominal degree of doping x_nom = 0, 0.05, 0.075, 0.1, 0.15, 0.2, 0.3, and 0.4) were synthesized by the sol–gel method using aqueous ammonia as a precipitator and were then annealed at 950°C for 60 min. From the data of X-ray powder diffraction analysis and local electron probe microanalysis, the maximum actual limit of doping of lanthanum ferrite with zinc was determined: x = 0.072. The dependence of the particle size on the Zn²⁺ content was found to be nonmonotonic. The magnetic characteristics (specific magnetization J, coercivity H_c, and magnetic susceptibility χ) of samples at temperatures of 300 and 100 K in fields of up to 1300 kA/m. It was shown that, with increasing degree of doping, J increases from 0.188 A m²/kg (at x = 0) to 0.245 A m²/kg (at x = 0.072), and χ varies nonmonotonically from 11.5 × 10^–6 (at x = 0) to 15.3 × 10^–6 (at x = 0.072) (at 300 K). With decreasing measurement temperature to 100 K, the magnetization and susceptibility monotonically increase.