INTRINSIC AND EXTRINSIC PERMEABILITY OF THIN FERROMAGNETIC LAYERS ANDINSULATOR-FERROMAGNETIC MULTILAYERS AS FUNCTION OF FREQUENCY - COMPARISON OF EXPERIENCE AND MODEL

Soft ferromagnetic thin films are attractive materials for read/write head applications because they exhibit a high magnetic permeability in the hundred MHz range. By contrast, due to their low electrical resis tivity, their processability at higher frequency is somewhat limited. Using Maxwell equations and the geometry of the processed material, we have developed a theoretical model of the frequency-dependent magneti c permeability useful for multilayers design. We have distinguished di fferent cases: extrinsic (measured) vs intrinsic permeability in magne tic thin films and magnetic-insulator multilayers, intrinsic vs extrin sic permeability in magnetic thin films, computed by the Newton iterat ive method. Using the well-known Landau-Lifshitz model for high freque ncy permeability, we have compared experimental and theoretical result s.