Remanence enhancement of single-phased isotropic nanostructured permanent magnets

Abstract

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 Mr, MS, Δ0, 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. © 1999 Elsevier Science B.V.