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US 5,184,335 AGranted
Method and system for erasing previously recorded domains in a magneto-optic recording medium
AssigneeMovid Information Technology, Inc.
InventorsMark H. Kryder, Han-Ping D. Shieh
Life of this patent
Estimating the term…
Abstract
Methods for directly over-writing the binary data value of a bit of digital data, stored in a particular one of a multiplicity of microscopic storage regions of a thin-film magneto-optic recording layer, in the absence of a substantial externally applied bias magnetic field, employ a magnetic material having a compensation temperature a few tens of degrees centigrade above room temperature. A source of energy is energized to heat the particular storage region to a sufficiently high temperature that the self-demagnetization field of the recording layer material inverts the net magnetic moment of that region. Multiple over-writing of the long-term stable stored data values can be provided.
Claims31
A method of selectively modifying information stored in a small region of a recording medium in a magneto-optic disk comprising the steps of:
- providing a thin-film layer of ferrimagnetic material as said recording medium having a compensation temperature a few tens of degrees centigrade above room temperature;
- creating said small region in said recording medium surrounded by a magnetic domain wall, said small region having a direction of magnetization opposite to the direction of magnetization in the region immediately outside said magnetic domain wall;
- associating the information with an existing direction of net magnetization of said small region at ambient temperature;
- and
- irradiating said small region with a beam of energy, said beam imparting sufficient energy to said small region to temporarily raise the temperature of at least part of said small region above said compensation temperature to cause self inversion of the direction of net magnetization exhibited by at least a portion of said small region after cooling to ambient temperature without requiring the use of both external magnetic bias field and internal biasing layer to erase said small region in said medium, whereby the information stored in said small region is modified.
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A method of reversing net magnetization in a selected region initially surrounded by a magnetic domain wall of a magneto-optic recording medium without requiring an externally applied bias magnetic field and internal biasing layer for reversing said net magnetization, said method comprising:
- providing a thin film layer of ferrimagnetic material as said medium having a compensation temperature sufficiently above room temperature to permit reversal of direction of net magnetization in a selected region initially surrounded by said magnetic domain wall of the recording medium;
- creating said selected region in said recording medium surrounded by said magnetic domain wall;
- and
- temporarily heating said selected region to a temperature above said compensation temperature and employing the internal magnetic forces created by the heated region itself to reverse the net magnetization in said selected region.
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A method of reversing the net magnetization of a selected previously magnetized local region of a thin film magneto-optic recording medium, comprising the steps of:
- employing a ferrimagnetic material having a perpendicular uniaxial anisotropy as the recording medium such that net magnetizations of regions of the medium lie normal to a plane containing said thin film medium;
- recording a domain by creating said selected local region so that said selected local region is magnetized and surrounded by a magnetic domain wall such that said selected local region maintains a direction of magnetization opposite to direction of magnetization in the region immediately outside said magnetic domain wall;
- and
- erasing said selected region of reversed magnetization by temporarily heating said created selected local region, without requiring an external magnetic biasing field and an internal bias layer for erasing said domain, to an elevated temperature at which the coercivity of the material in the created selected local region is low enough such that the internal magnetic forces created by the medium reverse the net magnetization of said selected region.
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A method of modifying information associated with a first domain of a magneto-optic recording medium having a ferrimagnetic thin film without requiring an external magnetic bias field and internal magnetic bias layer, said first domain being surrounded by a first magnetic domain wall and having an initial net magnetic moment in a first direction, comprising the steps of:
- producing a second smaller domain within said first domain, said second domain being surrounded by a second magnetic domain wall, and
- supplying heating radiation to cause the wall of said second domain to meet and annihilate at least a section of the wall of the first domain whereby the initial direction of the net magnetic moment in at least a portion of the first domain is reversed and information associated with said portion is modified.
A magneto-optic recording system comprising:
- a thin film ferrimagnetic medium having its net magnetization perpendicular to a surface of the film and a compensation temperature sufficiently above room temperature to facilitate self reversal of the direction of net magnetization exhibited at ambient temperature of a local region of the film which is initially surrounded by a magnetic domain wall an which has a magnetization reversed with respect to an initial magnetization direction of the medium;
- and
- means for heating said local region of reversed net magnetization surrounded by said magnetic domain wall above the compensation temperature to require only the internal magnetic forces created by the heated region to again reverse the net magnetization of said region when allowed to cool down to ambient temperature.
A magneto-optic recording disk system comprising:
- a discoidal substrate member formed of a substantially magnetic material, said member having a pair of generally circular, substantially parallel, spaced apart surfaces;
- a thin film magneto-optic recording material overlying at least one of said surfaces, said material being formulated to exhibit a perpendicular uniaxial anisotropy, such that a net magnetization of the material lies normal to said at least one surface, and said material having a compensation temperature sufficiently above room temperature to permit reversal of the direction of net magnetizations of regions each of which is surrounded by a magnetic domain wall and has a magnetization of direction reversed with respect to an initial magnetization direction of the medium;
- and
- means for temporarily heating a selected region of said recording material surrounded by a magnetic domain wall of said regions to an elevated temperature beyond said compensation temperature and then allowing said region to cool down to ambient temperature to again reverse the direction of net magnetization in said region without depending upon an application of an external magnetic bias field and a magnetic biasing layer within said recording disk.
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A method of successively reversing an instantaneous net magnetization in a selected region of a magneto-optic recording medium without requiring an external magnetic field and an internal magnetic bias layer, said method comprising:
- employing a ferrimagnetic thin film with net magnetization perpendicular to a plane containing said film as the recording medium, said film for producing a localized self demagnetizing field within said selected region when said selected region is heated to an elevated temperature higher than a compensation temperature of the film;
- and
- successively irradiating said selected region of the film with pulsed beams of energy, each pulsed beam serving to temporarily heat said selected region from ambient temperature to a temperature higher than said compensation temperature at which said localized self demagnetizing field created by the heated region in said thin film reverses said instantaneous net magnetization of said selected region, and allowing the region to cool down to ambient temperature between said successive irradiations, whereby the net magnetization of the region is repeatedly reversed.
A magneto-optic recording system comprising:
- a thin film magneto-optic recording medium having its net magnetization perpendicular to a plane containing said thin film medium, said medium being formulated to exhibit self inversion of the direction of net magnetization in at least a portion of a selected region surrounded by a magnetic domain wall thereof at an elevated temperature above a compensation temperature of said medium in the absence of an externally applied bias magnetic field, and internally applied bias layer;
- recording means for creating said selected region surrounded by a magnetic domain wall, said selected region having a direction of magnetization opposite to direction of magnetization in the region immediately outside said magnetic domain wall;
- and
- erasing means for temporarily irradiating at least portions of said selected region with electromagnetic radiation imparting sufficient energy to heat at least said portions from ambient temperature to said elevated temperature whereby the net magnetization of at least said portions is reversed without requiring an externally applied bias magnetic field and internal biasing layer for erasing said selected region surrounded by a magnetic domain wall when said selected region is cooled down to ambient temperature.
1 more element
A method of selectively modifying information stored in a small region of a magneto-optic disk comprising the steps of:
- providing a thin-film layer of ferrimagnetic material as a recording medium having a compensation temperature sufficiently above room temperature to permit reversal of direction of net magnetization in said small region;
- creating said small region in said recording medium so that said small region is surrounded by a magnetic domain wall, and so that said small region has a first direction of magnetization opposite to a second direction of magnetization in a region immediately outside said magnetic domain wall;
- associating the information with an existing direction of net magnetization of said small region at ambient temperature;
- and
- irradiating said small region with a beam of energy, said beam imparting sufficient energy to said small region to temporarily raise the temperature of at least part of said small region above said compensation temperature to cause self inversion of the direction of net magnetization exhibited by at least a portion of said small region after cooling said small region to ambient temperature without requiring an external magnetic bias field and an internal bias layer, each having a direction of said second direction of magnetization, applied to said medium to erase said small region in said medium, whereby the information stored in said small region is modified.
2 more elements
A magneto-optic recording system comprising:
- a thin film magneto-optic recording medium having its net magnetization perpendicular to a plane containing said thin film medium, said medium being formulated to exhibit self inversion of the direction of net magnetization in at least a portion of a selected region surrounded by a magnetic domain wall thereof at an elevated temperature above a compensation temperature of said medium;
- writing means for creating said selected region surrounded by a magnetic domain wall, said selected region having a first direction of magnetization opposite to a second direction of magnetization in a region immediately outside said magnetic domain wall;
- and
- erasing means for temporarily irradiating at least portions of said region surrounded by a magnetic domain wall, with electromagnetic radiation imparting sufficient energy to heat at least said portions from ambient temperature to said elevated temperature whereby the net magnetization of at least said portions is reversed to said second direction of magnetization without requiring an external magnetic bias field and an internal bias layer, each having a direction of said second direction of magnetization, applied to said medium for erasing said region surrounded by magnetic domain wall during cooldown of said region to ambient temperature.
1 more element
Dependencies are inferred from the claim text.