Magnetization reversal in a chain of oblate ellipsoids

The model of the chain of two oblate ellipsoids is modified by calculating exactly the magnetostatic interaction energy between the ellipsoids and tak ing into account the effects of the number of the ellipsoids. The angular d ependencies of the critical field H-eri and the coercivity H-c are determin ed analytically. The results show that the treatment of the magnetostatic i nteractions between the ellipsoids as dipole-dipole interactions is valid o nly for dimension ratio m (m = c/a, a and c are the major and minor semi-ax es of the oblate ellipsoid, respectively) approaching 1 or the separation r atio d (d = c/D. D is the separation between two neighboring ellipsoids) ap proaching O. The effective magnetic anisotropy constant K-u, H-eri and H-c increase with increasing n and K (n is the number of the ellipsoids, K is t he crystalline anisotropy constant). K-u and H-c decrease with decreasing m and d. For small m and large d, the effect of n on K-u, H-eri and H-c beco mes more pronounced. As It increases, the magnetization reversal mechanism of the chain tends more towards the parallel process. For constant K. the c ritical angle psi (0), increases with nt for large values of n, whereas the opposite effect occurs for small n. (C) 2000 Elsevier Science B.V. All rig hts reserved.