Magnetization Reversal in Magnetic Bilayer Systems

Magnetization reversal in magnetic soft/hard bilayer systems is studied analytically by means of a variational method for magnetic energies in a continuum model. The demagnetization curve is involved with nonlinear equations, and the solution is given implicitly in the form of Jacobi functions, which is valid for the total reversal process. Based on the non-trivial solutions, hysteresis loops, as well as the maximum energy product (BH)_\max versus thicknesses of soft/hard layers are obtained. With regard to (BH)_\max, improvement of the remanence competes with loss of coercive force. As a result, an optimum condition exists. For a given thickness of the hard layer, the optimum condition at which the largest (BH)_\max could be achieved is discussed, which is slightly different from previous works.