Magnetic properties of Fe-Al2O3 gel granular solids prepared by ball milling

Granular materials in the system Fex-(Al2O3)1 − x with different volume fractions of Fe have been prepared by ball milling pure Fe and sol-gel derived A12O3 gel powders up to 80 h. The final metal average particle size obtained ranged from 7–18 nm in different samples. We studied the variation of the magnetization and coercivity with the milling time. Coercivities as high as 550 × 10−4 T and 990 × 10−4 T at room temperature and at 5 K, respectively, were obtained for the x = 0.4 sample milled for 42 h. Presence of single domain and superparamagnetic particles may result in such high values. Low-temperature magnetization studies confirm the presence of superparamagnetic particles in the samples.