Patent ID: 7492550
Filing Date: 2009-02-17
Classification: G11B

Abstract:
1. A write head for unidirectional overwriting on a medium magnetizable in a longitudinal direction, said medium having a surface and moving in a single medium movement direction, said write head comprising: an inductive write element supplied with a current modulated with information to produce a basic magnetic field that embodies said information, said inductive write element having a gap therein; a first magnet pair of two permanent magnets disposed in said gap with respective magnetization comprising magnetization components perpendicular to the surface of the recording medium of said two permanent magnets in said first pair that are oriented oppositely to each other, said first magnet pair producing a first stray magnetic field and the two permanent magnets thereof being composed of permanent magnetic material selected so that a sum of said first stray magnetic field and said basic magnetic field is sufficient to longitudinally magnetize said recording medium only when said inductive write element is supplied with a predetermined current, and to produce substantially no erasure in said recording medium when said write element is supplied with no current or a current that is negative compared to said predetermined current; and a second magnet pair of two permanent magnets disposed upstream of said inductive write element relative to said direction of medium movement, with respective magnetizations of said two permanent magnets in said second magnet pair comprising magnetization components that are oriented oppositely to each other in a direction perpendicular to the surface of the recording medium, with the respective magnetizations of said two permanent magnets in said second magnet pair being oriented oppositely to the respective magnetizations of said two permanent magnets in said first magnet pair, said second magnet pair producing a second stray magnetic field having a strength sufficient to longitudinally magnetize said recording medium for recording said information on said recording medium.