MODELING OF THE ENHANCED REMANENCE OF NANOCRYSTALLINE, EXCHANGE-COUPLED HARD MAGNETIC GRAINS

A model that combines an analytical and a numerical approach allows fa st calculation of the enhanced remanence of an assembly of exchange-co upled, nanocrystalline, hard magnetic grains. It makes use of the shor t-range characteristic of the exchange coupling by dividing each grain of the distribution into a core and a boundary region and treating on ly the relevant energy terms in the different parts. Exchange coupling across the grain boundary is described as a domain wall function betw een two limiting angles and explains the increase of remanence with de creasing grain size. Magnetostatic interactions are treated in a mean- held approximation and are found to contribute a further small, grain size-independent effect. (C) 1998 Elsevier Science B.V. All rights res erved.