SURFACE ANISOTROPY OF A FINE GAMMA-FE2O3 PARTICLE

We investigate the effects of surface anisotropy of a single-domain ga mma-Fe2O3 fine particle (length 3000 Angstrom, aspect ratio 4.6:1) usi ng micromagnetics and the finite element method. We add surface anisot ropy energy, axially symmetric about the surface normal, to the total magnetic energy of the particle. We show that surface anisotropy of th e appropriate sign enhances the coercivity. Further, the surface magne tization tends to be tangential to the surface and the magnetization r eversal starts from the surface. Our simulation suggests that surface anisotropy might be an important mechanism for the coercivity enhancem ent in the surface-modified iron oxides. (C) 1996 American Institute o f Physics.