Secondary gap effect in narrow and wide track reproduce heads

The harmonic response of three dimensional magnetic reproduce heads with finite permeability is numerically computed by means of boundary integral equations. The results show that as the permeability of a head decreases, not only does the reproduce output level decrease, but the long wavelength response spectrum changes its shape as well. This phenomenon, known as the secondary gap effect, is analyzed in both two dimensions (and compared with a previous approximation) and, for the first time, in three dimensions (finite track width).