Magnetic and hyperfine properties of chemically synthesized nanocomposites of (Al2O3)x(Ni0.2Zn0.6Cu0.2Fe2O4)(1-x) (x=0.15, 0.30, 0.45)

(Al2O3),(Ni0.2Zn0.6Cu0.2Fe2O4)((1-x)) (x = 0.15, 0.30, 0.45) nanocomposites were synthesized by coprecipitation and sol-gel methods. The as-prepared samples were annealed at 400 degrees C to obtain the desired nanosystems. Particle sizes and crystallographic phases of the magnetic nanoparticles were evaluated from XRD and TEM observations. TEM observations revealed the formation of nanocrystalline phase in the amorphous matrix of aluminium oxide. High resolution TEM also hints that some nanoparticles were coated with aluminium oxides. Heat-treated samples were characterized by DC magnetization, AC hysteresis loops at 37 Hz and Mossbauer effect measurements. Mossbauer spectra of all the samples indicate the presence of relaxation in all the samples. DC magnetization curves have the typical nature of superparamagnetic particles which are also in good agreement with that of Mossbauer study. Coercive fields obtained from the observed AC hysteresis loops are quite low in the present samples which would be suitable for soft magnetic device applications. (c) 2007 Elsevier Ltd. All rights reserved.