Penetration depth and magnetic permeability calculations on GMI effect and comparison with measurements on CoFeB alloys

Through a proper application of a model proposed by Kuzminski and Lachowicz, giant magneto-impedance (GMI) data obtained on as-prepared and Joule heated CoFeB amorphous ribbons have been analyzed in order to obtain detailed information about how the electromagnetic penetration depth and transverse relative magnetic permeability evolve as a function of a longitudinal magnetic field and annealing conditions. When transverse permeability is enhanced (near the beginning of the crystallization process), impedance values reach a maximum, while when transverse magnetic permeability variations with the application of a longitudinal magnetic field are maximized, the best GMI response of the material is obtained.