Unusual magnetic recording applications utilizing highly anisotropic recording materials

The extreme anisotropy of certain magnetic recording tapes results in unusual recording properties. Oriented, low coercive force barium ferrite recording tapes are exceptionally resistant to erasure by hard-axis magnetic fields. This property makes it possible to anhysteretically contact duplicate digital signals from a barium ferrite recording tape with
H\min_{c}\max_{e}
(easy-axis) of 715 Oe to cobalt-doped γ-Fe
2
O
3
tapes with
H\min_{c}\max_{e}
of 875-1130 Oe, using hard-axis bias fields up to 2000 Oe. The large uniaxial magnetocrystalline anisotropy of oriented barium ferrite tapes also makes them unresponsive to recording-head fields with components along hard-axes-of-magnetization. Consequently, dual-layer barium ferrite recording tapes with in-plane easy-axes-of-magnetization oriented at +45° and -45°, respectively, to the longitudinal-tape-axis can be independently recorded, read, and erased using heads with gap-length parallel to the easy-axis of a selected layer. Signal amplitude losses on one layer, resulting from recording or erasing the other layer, are about 11% (1dB) for 27 flux transition/cm digital signals.