Magnetic properties of the granular alloy Fe10Ag90 as a function of annealing temperature

fe10ag90 granular alloys have been prepared using a sol-gel process, sintered at 300 °c and annealed at temperatures between 400 °c and 700 °c. the mean size of the iron particles, obtained from x-ray diffraction, is 30.0 ± 0.7 nm. due to the existence of a distribution of particle sizes in these samples, both blocked (bl) and superparamagnetic (spm) particles are present simultaneously, as confirmed by magnetization measurements at room temperature. ac susceptibility measurements as a function of temperature reveal a magnetic phase transition at about 770 °c, indicating the presence of particles exhibiting bulk behavior, in the samples annealed above 550 °c. the presence of these particles has been attributed to an atomic diffusion process between the grains, forming bulk-like multiple-domain fe particles having curie temperatures near that of bulk a-fe phase (tc = 770 °c).