Coercivity of a percolative magnetic system

A model that describes the behavior of the coercivity H_c, of coalescing Ni films, as a percolation phenomenon is presented. We show that there is a nonmonotonic dependence, of the coercive field as a function of the occupation probability p. This behavior is a function of cluster size and topology, and is independent of the growth direction of the thin film. Based on these ideas we predict theoretically, and confirm experimentally, the dependence of H_c as a function of external magnetic field orientation. For a [111] oriented fcc film, if p is less than the percolation threshold p_cr, a sixfold symmetry is observed. However, if p≈p_cr the percolation is isotropic.