Anisotropic reversible permeability effects in the magnetic reproduce process

The effect of an anisotropic, reversible medium permeability on the reproduce flux from an arbitrary recorded magnetization pattern has been calculated. It is shown that for normally oriented media the anisotropy of the permeability always acts to increase the reproduce flux. A 3-5 dB increase in short wavelength sensitivity is predicted in ac-biased recording due to this reproduce phenomenon. At short wavelengths, the effect of head-to-medium spacing is shown to assume a general form independent of the recorded magnetization pattern and dependent only on the geometric mean of the two orthogonal permeabilities. For short wavelengths and small head-to-medium spacings, a loss of approximately
\exp (-4\pi a/\lambda) (110 a/\lambda [dB])
is predicted for most media where
a
is the head-to-medium spacing and λ is the wavelength.