Computation of magnetic fields from recording surfaces with multiple tracks

Calculations of the magnetic fields emanating from a recorded surface that contains an infinite number of identical tracks are presented. The solutions are obtained by assuming that the magnetization is uniform through the thickness of the film and can be represented by Fourier series in the other two dimensions. Solutions are obtained for both longitudinal and vertical recording. To make these calculations useful Fourier distributions are obtained with arctan transitions that are both representative and easy to use. These magnetic fields are then used to calculate the voltage from an idealized reproduce head. Effects on the output voltage caused by track width, track separation, head registration, and transition lengths can then be calculated. Examples are given and it is shown that the effects can be large, compared to the usual infinite track width calculations, when the track width or the track separation become comparable to the recorded wavelength.