Reversal modes of the multilayer exchange-spring magnet

A one-dimensional micromagnetic model of the multilayer exchange-spring magnet is utilized for calculating the analytical expression of the differential susceptibility at the nucleation field in terms of structural parameters. The phase diagram in the plane of half-layer thicknesses is given for a Sm-Co/Fe multilayer, showing the critical line of chi (c) --> infinity, which is the boundary for the irreversible demagnetization mode. For thin layers the optimum soft-phase volume fraction is deduced. (C) 2001 Elsevier Science B.V. All rights reserved.