Analysis of magnetization processes in composite media grains

Composite grains, consisting of a subgrain with high anisotropy field coupled with a subgrain with zero anisotropy, are analyzed using a two-spin model. An analytical expression is given for the exchange coupling between the subgrains that minimizes the field required to reverse the magnetically hard layer. The results of the two-spin model are compared with those of a spin chain that represents an "exchange spring magnet." The limitations of the two-spin model are worked out. (C) 2006 American Institute of Physics.