Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
  • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
  • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
  • G11B11/10582—Record carriers characterised by the selection of the material or by the structure or form
  • G11B11/10586—Record carriers characterised by the selection of the material or by the structure or form characterised by the selection of the material
  • G11B11/10589—Details
  • G11B11/10591—Details for improving write-in properties, e.g. Curie-point temperature
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
  • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
  • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
  • G11B11/10532—Heads
  • G11B11/10534—Heads for recording by magnetising, demagnetising or transfer of magnetisation, by radiation, e.g. for thermomagnetic recording
  • G11B11/10536—Heads for recording by magnetising, demagnetising or transfer of magnetisation, by radiation, e.g. for thermomagnetic recording using thermic beams, e.g. lasers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
  • G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
  • G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
  • G11B11/10582—Record carriers characterised by the selection of the material or by the structure or form

Definitions

• the invention relates to a data storage system with thermally directly rewritable information, in which the information is overwritten by focusable radiation which can be converted into heat energy and which can be controlled with intensity which can be controlled in regions with a variable magnetization direction.
• the storage system includes a multi-layer structure with a magnetic storage layer and a magnetic control layer. This control layer serves as a field source for controlling the magnetization in the storage layer.
• magneto-optical storage systems information with a focused radiation pulse that is converted into heat, preferably a laser beam, can be written into a storage medium whose coercive field strength decreases with increasing temperature.
• the storage medium which is generally designed as a magneto-optical thin layer, has its preferred magnetic axis perpendicular to the flat sides of the storage layer.
• the magneto-optical storage medium becomes, in predetermined areas, approximately the order temperature, the so-called Curie temperature, at which a predetermined magnetization can be set in the resulting domains by an external magnetic field.
• the pattern of the magnetization in the domains represents the information stored as binary data.
• a laser beam of low intensity is supplied via a polarizer.
• the polarization of the light beam is rotated by a predetermined angle when the light beam is reflected by the storage layer (Kerr effect) or when it passes through the storage layer (Faraday effect).
• the size of the The angle of rotation is largely determined by the properties of the storage medium.
• the plane of polarization is rotated clockwise or counterclockwise.
• the change in polarization is converted by an analyzer into a change in the intensity of the light beam, which can be registered by a photodetector. By displaying the rotation, the information can be read out of the memory again.
• the written information can be erased with a laser beam during one revolution of the storage disk and new information can be written in during the following revolution.
• a heat beam can be erased and rewritten with the following beam.
• the magnetization is overwritten only in those domains in which new information is to be written in to overwrite.
• the control layer serves to generate a basic magnetic field. It consists of ferrimagnetic material with magnetization that changes depending on the temperature. Reading and overwriting takes place in separate magnetic areas with a two-beam laser system. Both the storage layer and the control layer are heated by the laser beam. If the control layer is heated above its compensation point T K , its direction of magnetization is reversed and at the same time increased. When the Curie temperature T of the storage layer is reached, this layer becomes writable and its magnetization is parallel to the magnetization in the control layer. When cooling below the compensation temperature T K of the control layer, the magnetization is reversed and the magnetization is then in the memory Layer opposed. The magnetization in the
• Control layer is transformed by magnetostatic interaction.
• the coercive field strengths of the two layers must therefore be matched to one another so that the magnetization in the control layer can be reversed by magnetostatic interaction, while the magnetization in the storage layer remains unchanged (US Pat. No. 4,649,519).
• Another known data storage system in which the writing, reading and erasing of the information takes place by means of radiation which can be focused and converted into heat energy, contains a multilayer structure with a magnetic storage layer as a data carrier and a control layer for overwriting stored information.
• a laser with controllable intensity is used to write the information.
• Control layer has a perpendicular magnetization and a relatively low coercive field strength at room temperature.
• a strong initialization field is applied to the control layer at room temperature before recording and ensures magnetization in the same direction.
• a laser beam with pulse modulation is directed onto the multilayer structure and the temperature is increased to such an extent that the magnetization disappears in both layers. This means that a bit is written into the control layer and is transferred to the storage layer during cooling by magnetic exchange coupling or magnetostatic coupling.
• the magnetization of the control layer With a low level of the laser beam, with which the multilayer structure is only heated below the Curie temperature of the control layer, the magnetization of the control layer remains unchanged and a different bit is written into the storage layer. Initialization and enrollment take place in separate areas.
• the information is deleted in the initialization area of the control layer so that it can be rewritten in the write area.
• an initialization field is required that deletes the data written in the control layer and at the same time does not change the data in the storage layer.
• the registered magnetic domains are stable due to magnetic wall friction.
• a material with a high coercive field strength is therefore required as the storage layer so that wall creep can be avoided and at the same time high demands must be placed on the homogeneity of the storage layer and the device temperature (DE-OS 36 19 618).
• Another known data storage system with thermally directly overwritable information contains a multilayer structure as a data carrier, the storage layer of which is separated from a control layer by an insulating layer which serves to control the temperature in the control layer.
• a laser beam with controllable intensity is used for writing, reading and erasing.
• the control layer generates a magnetic control field and thus a magnetic field orientation in the storage layer as a function of temperature.
• To write an O signal only the storage layer is heated by a laser beam of short time length and, for example, the O magnetization is written into the storage layer by a basic field source arranged above the data carrier.
• the control layer is also heated by a longer laser pulse and the charge pattern in the control layer is changed.
• the changed field profile is transferred to the storage layer.
• the charge pattern of the control layer has only a relatively small magnetizing effect on the storage layer.
• the thickness of the control layer must be chosen to be relatively large so that the dipole character of the charges disappears.
• the materials with this relatively high compensation temperature have a relatively low total magnetization because of the oppositely directed magnetizations in both sub-gratings. Accordingly, only small fields can be generated in the storage layer (European Offenlegungsschrift 0 217 096).
• the invention is based on the object of specifying a simple and effective data storage system in which the stored information can be overwritten directly without a separate deletion process.
• the invention is based on the knowledge that an increased magnetic penetration by the control layer is required to write stable domains in the storage layer and it consists in the features of claim 1.
• the additional magnetic switching field source generates a magnetization distribution in the control layer and thus a predetermined field distribution in the storage layer.
• a change in the temperature distribution in the control layer changes the magnetization distribution in this layer, which is impressed by the switching field source, and a predetermined change is thus obtained in the storage layer.
• Radiation with controllable intensity preferably a laser beam, is used, which can be controlled in three stages, for example. Only a relatively low laser power is required to read out the information.
• the laser power is increased to such an extent that the storage layer heats up above its critical temperature and below the critical temperature of the control layer and a zero signal is written in by the basic magnetic field.
• the control layer is also heated above its critical temperature by a laser pulse with a further increased intensity. It thus loses its shielding ability and the I signal is written in by the resulting field from the basic field and the substantially larger and opposite magnetic switching field.
• the insulating layer and the control layer are dimensioned such that the temperature of the control layer is still above it critical temperature and it has not yet regained its shielding ability when the storage layer cools below its critical temperature. The resulting field therefore remains effective in the registered domain of the storage layer.
• the write-capable area in the storage layer is thus magnetically switched approximately synchronously.
• the storage layer can preferably consist of ytterbium-terbium-iron-cobalt YtTbFeCo.
• Selenium is preferably suitable as the material for the insulating layer.
• a material is preferably selected as the control layer whose relative permeability ⁇ r at room temperature is at least 10, preferably at least 100, in particular at least 1000.
• Iron-cobalt-zircon FeCoZr with a relative one is particularly suitable
• the switching field source can consist, for example, of a permanent magnet made of samarium-cobalt SmCo, the field strength of which is preferably at least twice the field strength of the basic field source.
• an integrated permanent magnet can also be provided as the switching field source, which is designed as a thin film and is arranged as an additional layer under the control layer.
• a groove structure of the layers can be expedient.
• the substrate on which the multilayer structure is arranged can be provided with grooves on which the layers of the multilayer structure are successively deposited.
• FIG. 1 schematically illustrates the structure of a data storage system according to the invention.
• Diagrams according to FIGS. 2 and 3 serve to explain the direct overwriting.
• the diagram according to FIG. 4 illustrates properties of a special control layer.
• a write operation with the control layer according to FIG. 4 is indicated in FIG. 5.
• the diagram according to FIG. 6 illustrates properties of a further control layer.
• FIGS. 7 to 9 each show a special embodiment of a data storage system according to the invention.
• a data storage system contains a multilayer structure 1 with three layers.
• a storage layer 2 with a thickness of approximately 70 nm, for example, which can consist, for example, of terbium-iron-cobalt TbFeCo, preferably of ytterbium-terbium-iron-cobalt YbTbFeCo, is provided for data storage.
• An insulating layer 4 serves to control the heat diffusion from the storage layer to a control layer 6.
• the insulating layer 4 can preferably be made from selenium Se or silicon nitride Si 3 N 4 , but also, for example, from silicon oxide SiO 2 and from aluminum nitride Al 2 N 4 or from aluminum oxide Al 2 O 3 exist.
• a radiation source 8 is provided, which can preferably be a laser radiation source with an additionally controllable intensity and an output of, for example, approximately 5 mW.
• a focusing lens 10 is provided for focusing the laser beam 9.
• the storage layer 2 is assigned a basic field source 11, which can be a coil, for example, and supplies a basic magnetic field H 11 .
• an additional switching field source 12 is arranged, the diameter B of which can be approximately 20 ⁇ m, for example, and which is arranged at a distance A of approximately 10 ⁇ m, for example, below the control layer 6.
• a permanent magnet is suitable as the switching field source 12, which can preferably also be provided with a bowl-shaped magnetic yoke 15, the edge region of which serves to concentrate the switching field, preferably can consist of samarium cobalt SmCo and provides a switching field H 12 , the intensity of which is substantially greater than that The intensity of the basic field is H 11 .
• T At ambient temperature
• this field is short-circuited by the control layer 6 and thus shielded.
• a written information is read out in a known manner with the aid of the Kerr rotation after the reflection of the laser beam 3 or with the aid of the Faraday rotation after the laser beam 9 has passed through the storage layer 2.
• the laser beam 9 is directed onto the storage layer 2 with increased intensity and the latter is heated within an area 16.
• the temperature T is plotted over time t in the diagram in FIG.
• the temperature profile in the storage layer 2 is designated T 2 and the temperature profile in the control layer 6 is designated T 6 .
• T 2 the temperature profile in the storage layer 2
• T 6 the temperature profile in the control layer 6
• the storage layer is heated by the laser beam 9 and this layer is heated to a maximum temperature T 2max of, for example, 200 ° C.
• T 2K the critical temperature T 2K is reached, which corresponds approximately to the Curie temperature T c of the storage material, and the storage layer 2 becomes writable.
• the laser beam 9 is switched off, for example after about 40 ns, and the storage layer cools down again until it loses its writing ability again at time t 4 below its critical temperature T 2K .
• the control layer 6 is heated and he their maximum temperature T 6max is sufficient at time t 3 .
• This maximum temperature of, for example, 100 ° C. is lower than the critical temperature T 6K at which the control layer 6 loses its shielding ability.
• the insulating layer 4 is dimensioned such that this critical temperature T 6K is not reached when a zero signal is written.
• the shielding ability of the control layer 6 is thus retained when a zero signal is written.
• the impressed magnetization is fixed during cooling to below the critical temperature T 2K at time t 6 .
• the O signal is thus written into the storage layer 2 by the basic field H 11 during the time t 1 to t 4 .
• the relative critical temperatures T 2K / T 2 and T 6K / T 2 are plotted against time t.
• the T 6K / T 2 curve c illustrates the temperature profile in the storage layer 2.
• the quotient T Kr2 / T 2 is plotted in curve a.
• Curve b represents the quotient T 2K / T 2 and curve C shows the ratio T 6K / T 2 .
• the storage layer 2 receives a laser pulse 9 with increased intensity. The storage layer 2 is heated and at time t 1 its temperature T 2 exceeds the critical temperature T 2K and the storage layer 2 becomes writable.
• the temperature T 2 again becomes lower than the critical temperature T 2K and the quotient T 2K / T 2 becomes greater than 1.
• the storage layer is 2 writable.
• the intensity of the laser beam and the insulating layer are chosen so that the control layer 6 is sufficiently heated by heat diffusion.
• the quotient T 6 / T 2 is greater than the quotient T 6K / T 2.
• the critical temperature T 6K of the control layer 6 is exceeded and the control layer 6 loses its shielding ability.
• the control panel H 12 can Pass through area 16 in the storage layer 2.
• the storage layer 2 is writable, so that the resulting field H is effective in the region 16 in this period ⁇ t.
• the storage layer in the area 16 receives the magnetization direction of the resulting field H in this area regardless of the previous magnetization state.
• the I signal is thus written in by the switching field H 12 .
• the data storage system can be provided with a control layer 6 made of a material, the compensation temperature T K of which is substantially below the Curie temperature T c , as indicated in the diagram according to FIG. 4, in which the magnetization M is above the temperature T. is applied.
• This property has, for example, iron /
• Tb especially in the composition Tb x Fe y Co 1-xy , where x ⁇ 0.25 and y ⁇ 0.6.
• the magnetization M of this material is large at room temperature T A and then decreases to the compensation temperature T K and again reaches a maximum before it is zero again at the Curie temperature T c .
• the control layer 6 is heated approximately to the compensation temperature T K in order to write an O signal. Its magnetization M disappears and a “hole” is created in the control layer 6.
• the switching field H 12 reaches in the area 17 to the area 16 of the storage layer 2. With this control layer 6, the O signal is thus written in by the control panel H 12 .
• the temperature T is further increased by the laser beam 9 up to the temperature T m with maximum magnetization.
• the control layer 6 is soft magma in a central area 22 with this temperature T m below the area 16 of the storage layer 2 table and shields the switching field H 12 from the area 16 and the I signal is written through the basic field H 11 into the area 16 of the storage layer 2.
• the shielding is absent in an area 23 at the edge of the central area 22, but this ring-shaped area 23 lies outside the writable area 16 of the storage layer 2.
• the magnetization M increases with increasing temperature T up to a maximum value and then drops steeply just below the Curie temperature T c .
• the quality factor Q shows a decrease up to the Curie temperature T c .
• This property has, for example, terbium-iron-cobalt with the composition Tb x Fe y Co 1-xy , where X ⁇ 0.2 and y ⁇ 0.7.
• the temperature is increased up to the temperature T o , at which the control layer 6 in the region 22 has no shielding effect due to the high quality factor Q and the switching field H 12 penetrates to the writable region 16 of the storage layer 2.
• T I with high magnetization M I and low magnetic anisotropy K
• the area 22 becomes soft magnetic, it shields the switching field H 12 and the I signal is written in by the basic field H 11 .
• the multilayer structure with the storage layer 2, the insulating layer 4 and the control layer 6 is arranged on a substrate 20, which can be made of glass, for example.
• a switching field source 13 is in the multilayer structure as a hard magnetic thin layer with a periodic magnetization pattern, for example with regions of magnetization 23 which are alternately opposed to one another. integrated, whose period length C corresponds to the distance between adjacent data tracks.
• a switching field (not specified in more detail) emerges, which is shielded upwards by the control layer 6 at room temperature.
• the length C of these areas can be approximately 1.6 ⁇ m, for example.
• the substrate 20 is provided with grooves 21, the width D of which can be approximately 1 ⁇ m, for example.
• the substrate 20 is provided with a magneto-optical storage layer 2, which is separated from the control layer 6 by an insulating layer 4.
• this multilayer structure is provided with a switching field source 14 as a thin film, which has a preferred direction for the magnetization perpendicular to the film plane.
• This switching field source 14 can consist, for example, of manganese bismuth MnBi, preferably of terbium-cobalt TbCo, in particular of cobalt-palladium CoPd.
• This thin layer can preferably consist of several layers which are applied one after the other.
• the depth a of the grooves 21 is preferably selected to be equal to the product of an odd number with a quarter of the wavelength ( ⁇ / 4) of the light in the substrate 20 and can be, for example, approximately 0.25 ⁇ m.
• a common switching field source 14 is assigned two multilayer structures, each of which contains a storage layer 2 or 3, an insulating layer 4 or 5 and a control layer 6 or 7. In this embodiment, a double memory content of the system is obtained.

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• 1988
  • 1988-04-05 DE DE19883811375 patent/DE3811375A1/de active Granted
• 1989
  • 1989-03-10 EP EP19890903147 patent/EP0409848A1/de not_active Withdrawn
  • 1989-03-10 WO PCT/EP1989/000253 patent/WO1989009991A1/de not_active Application Discontinuation

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