MICROSTRUCTURE AND MAGNETIC PROPERTIES OF RARE-EARTH SUBSTITUTED STRONTIUM FERRITE NANOPARTICLES
C. DOROFTEI, E. REZLESCU, P. D. POPA, N. REZLESCU

Abstract. Rare-earth substituted strontium ferrite nanopowders SrFe_12-xR_xO₁₉ (R = La, Gd and Er; x = 0.2, 0.5 and 1) were prepared by sol-gel-autocombustion method. In this method one realizes an optimum mixing of ions on the atomic level so that the crystallization of hexaferrite particles can occurs at relatively low temperatures. The combusted powders were annealed at different temperatures (800, 900 and 1 000°C) for various annealing times (5, 10, 20, 40, 80, 160 and 320 minutes). The results of X-ray diffraction measurements showed the M-type hexagonal structure formation by heat treatments. Magnetic properties as well as microstructure depend on heat treatment conditions. We believe that further investigation are necessary to explain why in the nanoparticles system the heat treatment time influence on the coercivity is much stronger compared to the heat treatment temperature.