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 nanostru ctured permanent magnetic materials can be written as M-r/M-s, = 0.5 + 1.8 Delta(0)/L, where M-r, M-s, Delta(0), and L are the remanence, saturation m agnetization, exchange length and the average grain size, respectively. Thi s formula reveals that our calculated remanence is larger than the predicti ons of the Stoner-Wohlfarth model for all particle sizes, and that remanenc e enhancement increases with decreasing grain size. Application of the rela tion to melt-spun Nd-Fe-B magnets shows good agreement with available exper imental and numerical data. (C) 1999 Elsevier Science B.V. All rights reser ved.