Demagnetization theory for longitudinal recording

The reproduce head flux function for a longitudinally, sinusoidally magnetized tape is calculated on the assumption that the tape first demagnetizes irreversibly and then remagnetizes reversibly. In contrast to previous work, wherein all changes were considered reversible, the present calculation leads to a nonvanishing loss at short wavelengths. The loss is, however, quite small for conventional γFe2O3tape, ranging from 4.5 dB to 8 dB for the cases of incontact reproduction with magnetic and nonmagnetic heads, respectively. It is concluded that little justification exists for the use of higher coercive force tape materials with the present values of tape remanence, and that tapes with the highest possible oxide packing fraction will always give the highest ouput.