Thermal dependence of coercivity in soft magnetic nanocrystals

An important group of soft magnetic nanocrystals is that formed by α-Fe(Si) nanocrystals (around 10-nm grain size) embedded in a residual amorphous matrix. A simple phenomenological theory that takes into account the two-phase character based on the random anisotropy approximation has been developed. The percentage of crystallized material $x$ is taken into account and a quantitative expression for the thermal dependence of coercivity, considering the two-phase character of the samples, has been obtained. The good fit between the experimental curves and the theoretical ones of nanocrystalline ${\mathrm{Fe}}_{73.5}{\mathrm{Si}}_{13.5}{\mathrm{B}}_9{\mathrm{Cu}}_1{\mathrm{Ta}}_3$ samples with different crystallized volume fraction is discussed.