EXCHANGE-ANISOTROPY IN FILMS, AND THE PROBLEM OF INVERTED HYSTERESIS LOOPS

The inverted hysteresis loop is claimed to be possible, in an exchange-coupled bilayer, when a magnetically soft material is affected by the demagnetizing field of the hard material. These demagnetizing fields are caused by the charge on the surfaces, neglected in all the theories that assume a strictly one-dimensional structure, in an infinite material. For these one-dimensional models, an analytic solution is presented, which reduces the computation from a numerical integration of a set of differential equations to the solution of an algebraic, transcendental equation (which contains elliptic functions) for fitting only the boundary conditions. It may then be feasible to introduce at least an approximation for the demagnetizing effect of the surfaces in a finite sample.