Remanence enhancement of single-phased isotropic nanostructured permanent magnets

Based on a simple micromagnet model, we show that an analytical expression for reduced remanence in single-phased and single-domain isotropic nanostructured permanent magnetic materials can be written as Mr/MS=0.5+1.8Δ0/L, where M r , M S , Δ 0 , and L are the remanence, saturation magnetization, exchange length and the average grain size, respectively. This formula reveals that our calculated remanence is larger than the predictions of the Stoner–Wohlfarth model for all particle sizes, and that remanence enhancement increases with decreasing grain size. Application of the relation to melt-spun Nd–Fe–B magnets shows good agreement with available experimental and numerical data.