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Thermomagnetic Writing/Magnetoresistive Reading On Ferromagnetic Disk

IP.com Disclosure Number: IPCOM000121145D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

David Shieh, HP: AUTHOR

Abstract

Described is a method to achieve high density recording using thermomagnetic recording, magnetoresistive (MR) read-out in ferromagnetic thin films. Thermomagnetic writing forms sub-micron domains at high data rate; MR readout eliminates polarization optics and results in lightweight heads. High saturation magnetization (Ms) ferromagnetic media provides large read-out signal. In addition, optical servo and "read after write" can be a part of the head's function.

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Thermomagnetic Writing/Magnetoresistive Reading On Ferromagnetic Disk

      Described is a method to achieve high density recording
using thermomagnetic recording, magnetoresistive (MR) read-out in
ferromagnetic thin films.  Thermomagnetic writing forms sub-micron
domains at high data rate; MR readout eliminates polarization optics
and results in lightweight heads.  High saturation magnetization (Ms)
ferromagnetic media provides large read-out signal.  In addition,
optical servo and "read after write" can be a part of the head's
function.

      Ferromagnetic thin films, such as modulated Co/Pt and Co/Pd [1]
have high perpendicular anisotrophy (>10-6erg/cm3) and coercivity
(several KOe, depending upon fabrication methods).  Unlike rare
earth- transition metal (RE-TM) where RE and TM subnetworks are
antiferromagnetically coupled, Co and Pt (or Pd) are
ferromagnetically coupled.  Therefore, Ms is of several hundred
emu/cm3, comparable to that of CoCr or y-iron oxide.  High Ms media
is of advantages for MR readout where signal is proportional to
magnetic flux.  Two mm track width MR head has been demonstrated to
sense 0.3 mm domains [2].  The amount of flux into MR sensor is of
the same magnitude as that from 0.8 mm diameter domains in Co/Pt
films.  Since flux is inversely proportional to the spacing of media
and the MR head, a flying head is required to obtain adequate
read-out signal.

      An implementation of the optical/MR head recording system is
shown in the figure.  The MR and optical heads are on the same
slider.  The spacing between the two heads is dictated by the width
of MR head (including shielding)...