JP4331180B2 - Recording / playback device - Google Patents

Description

  The present invention relates to a recording / reproducing apparatus, and more particularly to a recording / reproducing apparatus capable of recording information using spin-polarized electrons on a recording medium.

  At present, a typical example of a low bit cost file memory is a hard disk, but there is a demand for further increase in capacity, that is, further improvement in surface recording density.

  However, it has been pointed out that when a bit cell is simply miniaturized, information may be lost due to the problem of thermal fluctuation. In order to prevent this, it is necessary to increase the magnetic anisotropy of the recording medium to enhance the stability of the magnetization. In this case, it is necessary to apply a large magnetic field to a minute portion. Therefore, the method of rewriting the magnetization direction of the recording medium by applying a magnetic field from the head (probe) is expected to have a limit from the above viewpoint.

  On the other hand, in the spin-injection magnetic recording method that is expected to be applied to the next generation MRAM (Magnetic Random Access Memory), the magnetization direction of the magnetization recording layer included in the magnetoresistive effect element by spin-polarized electrons Information is recorded by reversing at a high speed. Since the recording current is reduced when the element size is reduced, the recording method is advantageous for improving the recording density.

  As a recording method planned for a normal MRAM, the magnetization direction of the magnetization recording layer is determined by the direction in which electrons flow. Reproduction of recorded information is performed by detecting a change in resistance of the magnetoresistive element according to the direction of recording magnetization of the magnetization recording layer, for example, as a voltage change.

  An example in which this recording principle is applied to a recording device called a so-called probe memory or MEMS (Micro Electro Mechanical Systems) memory that reads information on a flat medium by a probe instead of a semiconductor memory using wiring such as MRAM. It is disclosed (see Patent Document 1).

  However, since a method in which the probe electrode is brought into ohmic contact with the recording medium and a conductive current flows is employed here, the problem that the contact resistance rides on the resistance to be read as noise, and further the problem of wear of the probe or the recording medium There is.

  On the other hand, the field emission type electron beam is considered as a promising means capable of supplying a current in a non-contact manner from the probe electrode toward the recording medium (see Patent Document 2). The electron emission region is extremely fine, about 10 nm or less, and the temperature of the ultrafine region is selectively heated or heated, or a conductive current is selectively passed through the fine region to allow information Recording or playback is possible.

However, the combination of this principle and the spin injection recording principle is not easy. This is because it is difficult to supply a field emission type electron beam from the recording medium side to the probe side, so that information rewriting is attempted even if it is applied to an element that rewrites information according to the direction of current as described above. I can't.
JP 2004-193595 A JP 2001-250201 A

  The present invention provides a recording / reproducing apparatus that can eliminate the contact resistance between a head and a recording medium, and that can have a large capacity and low power consumption.

A recording / reproducing apparatus according to one aspect of the present invention includes a recording medium including a magnetic recording layer in which a magnetization direction changes and a plurality of magnetic cells in which information is recorded, and a space or an insulating layer above the recording medium. is disposed over, and comprises a first magnetization pinned layer whose magnetization direction is fixed, and a first head for writing one of the binary information by supplying electrons spin-polarized in the magnetic cell, wherein Binary information is provided by supplying spin-polarized electrons to the magnetic cell, which includes a second magnetization pinned layer which is disposed above the recording medium via a space or an insulating layer and whose magnetization direction is fixed. And a magnetization direction of the first magnetization pinned layer is opposite to the magnetization direction of the second magnetization pinned layer .

  According to the present invention, it is possible to provide a recording / reproducing apparatus capable of eliminating the contact resistance between the head and the recording medium, and capable of increasing the capacity and reducing the power consumption.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, elements having the same function and configuration are denoted by the same reference numerals, and redundant description will be given only when necessary.

(First embodiment)
In the example of the present invention, when one or two heads (probes) are arranged above a rotating recording medium such as an HDD (hard disk), or more than 1000 cantilevers are installed in one chip, As in the case of parallel processing at the same time, a type of memory (storage) in which the head moves above the recording medium and records and reproduces information is assumed. Thus, as compared with a so-called semiconductor memory in which wiring is always connected to one recording cell, it is not necessary to consider an obstacle to miniaturization such as a short channel effect (of a transistor).

  FIG. 1 is a sectional view showing a configuration of a recording / reproducing apparatus according to the first embodiment of the present invention. The recording / reproducing apparatus includes a recording medium 10 on which information is recorded and a head 20 (in this embodiment, two heads 20-1 and 20-2) that records information on the recording medium 10.

  The recording medium 10 includes a conductive layer 18 provided on the substrate 11, an insulating layer 12 provided on the conductive layer 18, and a plurality of magnetic cells 14 provided in the insulating layer 12 on the conductive layer 18. It has. The plurality of magnetic cells 14 are regularly arranged via the insulating layer 12. That is, the plurality of magnetic cells 14 are electrically insulated by the insulating layer 12. Each magnetic cell 14 is electrically connected to a conductive layer 18, and the conductive layer 18 is grounded.

For example, silicon is used as the substrate 11. If flatness can be secured, inexpensive glass may be used. As the insulating layer 12, for example, a high-resistance insulator (alumina (Al ₂ O ₃ ), silicon oxide film, or the like) is used.

  The magnetic layer included in the head 20 and the magnetic layer included in the recording medium 10 are disposed so as not to be in physical contact. For this purpose, the protective film 13 may be provided on the upper surface of the recording medium 10 (the surface facing the head 20). Further, a protective film may be provided on the bottom surface of the head 20 (the surface facing the recording medium 10). The protective film 13 is preferably a thin insulating film. For example, DLC (diamond-like carbon) is preferable because wear resistance is also obtained.

The magnetic cell 14 is composed of a magnetization recording layer (free layer) 17. The recording layer 17 is made of a ferromagnetic material, and the magnetization direction changes (inverts). As the recording layer 17, an alloy containing at least one element selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), and chromium (Cr), “Permalloy”, NiFe alloys, or CoNbZr alloys, FeTaC alloys, CoTaZr alloys, FeAlSi alloys, FeB alloys, CoFeB alloys, and other soft magnetic materials, Heusler alloys, CrO ₂ , Fe ₃ O ₄ , La _1-X Examples thereof include half-metal magnetic oxides and nitrides such as Sr _X MnO ₃ .

  Furthermore, those normally classified as hard magnetic materials such as FePt alloys can also be used. That is, it is only necessary to appropriately select and use one of these materials having magnetic properties according to the application (including the hard magnetic material, the magnetization reversal is possible regardless of the coercive force, which is a feature of the spin injection principle. One of these).

  For the purpose of lowering the current value (critical current value) at which spin injection magnetization reversal (current is passed directly through the magnetic cell and the magnetization is reversed by the action of the spin of the electrons), the recording layer 17 is made of a Ru layer. You may comprise by the multilayer film which divides. FIG. 1 shows the simplest configuration.

  The recording layer 17 is required to have a coercive force or magnetic anisotropy sufficient to withstand thermal fluctuations. The coercive force required for the recording layer 17 depends on the size of the recording bit to be written, and a larger coercive force is required as the recording bit becomes smaller.

  The magnetization direction of the recording layer 17 is, for example, a direction substantially perpendicular to the film surface. The thick arrow shown in FIG. 1 indicates the magnetization direction. However, the present invention is not limited to this, and the magnetization direction of the recording layer 17 may be an in-film direction. However, if the miniaturization of the magnetic cell proceeds, the perpendicular magnetization will naturally become advantageous.

  The head 20-1 includes a conductive layer 21-1 to which electrons are supplied, and a magnetization fixed layer (pinned layer) 22-1 provided at the tip of the conductive layer 21-1 and having a fixed magnetization direction. Yes. That is, the fixed layer 22-1 is disposed on the side facing the recording medium 10. In addition, if the conductivity of the fixing layer 22-1 is sufficient, the entire head may be composed of only the fixing layer.

The pinned layer 22-1 is made of a ferromagnetic material, and the magnetization direction is fixed. For example, the film thickness of the pinned layer 22-1 is thicker than the film thickness of the recording layer 17 in order to fix the magnetization direction. Alternatively, the magnetization direction may be fixed by exchange coupling by adding an antiferromagnetic layer to the ferromagnetic layer. As the ferromagnetic layer, metals such as Fe, Co, Ni, Mn, and Cr, or alloys thereof are used. As the antiferromagnetic layer, FeMn alloy, PtMn alloy, PtCrMn alloy, NiMn alloy, IrMn alloy, NiO, Fe ₂ O ₃ or the like is used. Further, the fixing layer 22-1 may be formed of a multilayer film that is separated by a Ru layer.

  For example, the head 20-1 is disposed at a predetermined distance from the recording medium 10 and is disposed so as not to come into physical contact. The distance between the recording medium and the head needs to be less than or equal to the mean free path of electrons. At a distance that satisfies this condition, the spin polarization of the electrons is generally maintained. Here, the mean free path of electrons depends on the kind of gas, the gas pressure, and the energy of electrons, but in the case of nitrogen, which is one of the main components of air, the mean free path at atmospheric pressure is at least 150 nm. (It will be longer if the pressure is reduced). Preferably, this distance is 50 nm or less.

  In addition, if the distance between the recording medium and the head is too small, the head contacts the recording medium. As a result, the recording medium and the head are worn out (so-called head crash). Therefore, the distance between the recording medium and the head is set so as not to contact.

  The magnetization direction of the pinned layer 22-1 is a direction perpendicular to the film surface, like the recording layer 17. That is, when the easy axis of the recording layer 17 is perpendicular to the film surface, the easy axis of the pinned layer 22-1 is also required to be perpendicular to the upper surface of the recording medium 10.

  However, even if the magnetization direction of the pinned layer 22-1 on the head side is deviated by about 20 ° from the perfect perpendicular direction to the film surface, for example, the recording layer 17 has a magnetic anisotropy in the perpendicular direction to the film surface. For example, the magnetization direction of the recording layer 17 can be aligned substantially upward or downward. That is, the magnetization directions of the recording layer 17 and the pinned layer 22-1 do not have to be completely the same direction, and some deviation is allowed.

  Conversely, the same applies to the case where the magnetization direction of the fixed layer 22-1 on the head side is perpendicular to the film surface and the magnetization direction of the recording layer 17 is shifted by about 20 °. That is, since a slight deviation in the magnetization direction can be allowed, if the yield can be improved by allowing this, a deviation in the magnetization direction is allowed to some extent.

  A bias circuit 30 for causing field emission from the head 20-1 is connected to the head 20-1 and the recording medium 10. The field emission means that electrons are directly emitted from the head 20-1 toward the recording medium 10 by forming a high potential gradient (electric field) on the electron emission surface of the head 20-1.

  The bias circuit 30 supplies a negative potential to the head 20-1 and supplies a ground potential to the recording medium 10 (specifically, the conductive layer 18). That is, the bias circuit 30 applies a negative voltage between the head 20-1 and the recording medium 10. Due to the action of the bias circuit 30, electrons can flow from the head 20-1 to the recording medium 10.

  Similarly, the head 20-2 includes a conductive layer 21-2 to which electrons are supplied and a magnetization fixed layer 22-2 provided at the tip of the conductive layer 21-2 and having a fixed magnetization direction. . The head 20-2 has the same configuration as the head 20-1, except that the magnetization direction of the pinned layer 22-2 is opposite to that of the pinned layer 22-1. Of course, the bias circuit 30 is also connected to the head 20-2.

  FIG. 2 is a schematic diagram for explaining the drive units 40-1 and 40-2 for driving the heads 20-1 and 20-2. For example, the arrangement of the two heads 20-1 and 20-2 is as shown in FIG. That is, two heads (one set of heads) that move completely independently are arranged above the recording medium 10, and each head servos, reads an address, and reads a desired address in the same manner as a general hard disk mechanism. “0” or “1” is recorded at a specific position.

  However, since it is difficult to bring the two heads close to each other, some data buffer is required when writing different data to adjacent bits. Note that the number of heads is not limited to two, and as with a general hard disk, several disks may be combined and two heads (one set of heads) may be arranged for each disk.

  Hereinafter, an example of a drive unit for driving the head will be described. The recording / reproducing apparatus includes a drive unit 40-1 for controlling the relative positional relationship between the head 20-1 and the upper surface of the recording medium 10. The drive unit 40-1 includes a slider 41-1 that moves on the upper surface of the recording medium 10, and a drive circuit 42-1 that controls the operation of the slider 41-1.

  A head 20-1 is provided at the tip of the slider 41-1. The head 20-1 is disposed at a predetermined distance from the recording medium 10 by the slider 41-1, and is disposed so as not to come into physical contact. The recording / reproducing apparatus also includes a motor 43 for rotating the recording medium 10.

  Similarly, the recording / reproducing apparatus includes a driving unit 40-2 for controlling the relative positional relationship between the head 20-2 and the upper surface of the recording medium 10, and the driving unit 40-2 includes the recording medium 10. And a drive circuit 42-2 for controlling the slider 41-2.

  Then, the disk-shaped recording medium 10 is rotated using the motor 43. Further, the slider is moved in the radial direction of the disk. Thereby, the head can be moved to a desired specific position.

Next, the operation of the thus configured recording / reproducing apparatus will be described. When recording information, the head 20-1 moves above the target magnetic cell 14, and a negative potential is supplied from the bias circuit 30 to the head 20-1. Further, the ground potential is supplied from the bias circuit 30 to the recording medium 10. As a result, a potential difference is generated between the head 20-1 and the recording medium 10, and electrons (electron flow e ⁻ ) flow from the head 20-1 toward the recording medium 10 in a non-contact manner by a principle such as field emission.

  When the electrons pass through the pinned layer 22-1 whose magnetization direction is fixed, the electrons have a spin in the same direction as the magnetization direction of the pinned layer 22-1 (spin polarization). That is, electrons having a spin opposite to the magnetization direction of the pinned layer 22-1 are reflected from the upper surface of the pinned layer 22-1. On the other hand, electrons having spins in the same direction as the magnetization direction of the pinned layer 22-1 pass through the pinned layer 22-1.

  When electrons having a spin in the same direction as the magnetization direction (for example, downward) of the pinned layer 22-1 flow to the recording layer 17, the angular momentum of the spin is transmitted to the recording layer 17. As a result, the magnetization direction of the recording layer 17 is aligned with the same direction as the magnetization direction of the pinned layer 22-1.

  When the recording layer 17 is magnetized in the opposite direction (assuming the above operation is a “0” write operation, a “1” write operation), the fixed layer 22 magnetized in the opposite direction (upward) to the fixed layer 22-1. -2 having -2. Similarly, the “1” write operation can be realized by flowing electrons from the head 20-2 to the recording medium 10.

  As described above in detail, according to the present embodiment, electrons can be supplied from the head toward the recording medium in a non-contact manner, so that the contact resistance between the head and the recording medium can be eliminated. Thereby, wear of the head and the recording medium can be reduced.

  Further, the magnetization direction of the recording layer 17 is reversed using a spin injection magnetization reversal method. In this case, when the size of the magnetic cell 14 is reduced, the recording current is also reduced. Thereby, the recording density of the recording medium 10 can be improved, and as a result, the recording medium 10 can be miniaturized. Further, since the recording current can be reduced, power consumption can be reduced.

  In this embodiment, the configuration of a recording medium and a pair of heads (probes) is mainly described. However, the type is one in which hundreds and thousands of probes are arranged and the recording medium is moved by an XY actuator. It can be applied to other storages.

  Specifically, the recording medium is placed on an XY actuator, and the XY actuator controls the position of the recording medium with respect to the probe. Then, a recording medium having a plurality of tracks in a straight line is precisely sent in the track direction and the vertical direction to determine the recording and reproduction positions.

  In such an XY actuator system, each probe is responsible for each medium area. Therefore, if this medium area is considered as a block of each probe, the same operation as in the case of one set of heads is realized. be able to. For example, the same operation can be realized if two probes having opposite magnetizations are arranged as one set for each block.

(Second Embodiment)
The second embodiment is another configuration example of the magnetic cell 14 included in the recording medium 10, and further configured to reproduce the recorded information of the magnetic cell 14 using the head shown in the first embodiment. It is a thing.

  FIG. 3 is a cross-sectional view showing a configuration of a recording / reproducing apparatus according to the second embodiment of the present invention. The magnetic cell 14 has a laminated structure including a magnetization fixed layer (pinned layer) 15, a magnetization recording layer (free layer) 17, and a nonmagnetic layer 16 provided between the fixed layer 15 and the recording layer 17. is there. The configuration of the recording layer 17 is the same as that in the first embodiment.

As the nonmagnetic layer 16, an insulating layer, a metal layer, or a mixed crystal thereof can be used. As the insulating layer, Al ₂ O ₃ , MgO, or the like is used. As the metal layer, any one of nonmagnetic metal elements such as Cu, Ag, Au, or an alloy thereof can be used. When an insulating layer is used as the nonmagnetic layer 16, a TMR (Tunneling Magnetoresistive) element utilizing a tunnel magnetoresistive effect is obtained, and when a metal layer is used, a GMR (Giant Magnetoresistive) element is obtained. These are collectively called an MR (Magnetoresistive) element.

  The pinned layer 15 is made of a ferromagnetic material, and the magnetization direction is fixed. For example, the film thickness of the pinned layer 15 is larger than the film thickness of the recording layer 17 in order to fix the magnetization direction. Alternatively, the magnetization direction may be fixed by exchange coupling by adding an antiferromagnetic layer to the ferromagnetic layer.

  For the purpose of, for example, reducing the critical current value at which spin injection magnetization reversal occurs, the pinned layer 15 and the recording layer 17 may be formed of a multilayer film separated by Ru layers, or a plurality of pinned layers, a plurality of recording layers, The layers may be alternately stacked. FIG. 3 shows the simplest configuration.

FIG. 4 is a cross-sectional view showing another example of the fixing layer 15. The pinned layer 15 is formed by laminating a ferromagnetic layer 15-2 and an antiferromagnetic layer 15-1. As the ferromagnetic layer 15-2, a metal such as Fe, Co, Ni, Mn, and Cr or an alloy thereof is used. As the antiferromagnetic layer 15-1, an FeMn alloy, a PtMn alloy, a PtCrMn alloy, a NiMn alloy, an IrMn alloy, NiO, Fe ₂ O ₃ or the like is used. As described above, the magnetization direction of the pinned layer 15 is fixed in one direction by using the exchange coupling between the antiferromagnetic layer 15-1 and the ferromagnetic layer 15-2.

  Further, the magnetization of the ferromagnetic layer 15-2 may be fixed by a hard magnetic layer provided adjacent thereto. Alternatively, a hard magnetic layer may be used for the pinned layer 15 itself. As the hard magnetic layer in this case, a magnetic material such as a CoPt alloy, an FePt alloy, a CoCrPt alloy, an SmCo alloy, or an NdFeB alloy can be used.

  FIG. 5 is a cross-sectional view showing another example of the fixing layer 15. The pinned layer 15 has a SAF (Synthetic Anti-Ferromagnet) structure in which a ferromagnetic layer 15-4 / nonmagnetic layer 15-3 / ferromagnetic layer 15-2 / antiferromagnetic layer 15-1 are laminated. . As the ferromagnetic layer 15-4, a metal such as Fe, Co, Ni, Mn and Cr or an alloy thereof is used. Ru or the like is used as the nonmagnetic layer 15-3.

  The magnetic cell 14 configured as described above has a ferromagnetic tunnel junction, and a current flows through the nonmagnetic layer 16. The magnetic cell 14 has a tunneling magnetoresistive effect in which the magnitude of the tunneling current changes depending on whether the magnetization directions of the pinned layer 15 and the recording layer 17 are parallel or antiparallel. Have That is, the resistance value of the magnetic cell 14 takes a minimum value when the magnetization directions of the fixed layer 15 and the recording layer 17 are parallel, and takes a maximum value when the magnetization direction is antiparallel. Thereby, the magnetic cell 14 can store binary information with “1” when the resistance value is small and “0” when the resistance value is large.

  The recording layer 17 is required to have a coercive force or magnetic anisotropy sufficient to withstand thermal fluctuations. The coercive force required for the recording layer 17 depends on the size of the recording bit to be written, and a larger coercive force is required as the recording bit becomes smaller. The pinned layer 15 is required to have a larger coercive force or magnetic anisotropy than the recording layer 17.

  For example, the magnetization directions of the recording layer 17 and the pinned layer 15 are substantially perpendicular to the film surface. The thick arrows shown in each magnetic layer in FIG. 3 indicate the magnetization direction. However, the present invention is not limited to this, and the magnetization directions of the recording layer 17 and the pinned layer 15 may be in-film directions. The configuration in which the magnetization direction of each layer is the in-film direction will be described later.

Next, the operation of the thus configured recording / reproducing apparatus will be described. When recording information, the head 20-1 moves above the target magnetic cell, and a negative potential is supplied from the bias circuit 30 there. Further, the ground potential is supplied from the bias circuit 30 to the recording medium 10. As a result, a potential difference is generated between the head 20-1 and the recording medium 10, and electrons (electron flow e ⁻ ) flow from the head 20-1 toward the recording medium 10 in a non-contact manner by a principle such as field emission.

  When the electrons pass through the pinned layer 22-1 whose magnetization direction is fixed, the electrons have spins in the same direction as the magnetization direction of the pinned layer 22-1. When electrons having a spin in the same direction as the magnetization direction of the pinned layer 22-1 flow through the recording layer 17, the angular momentum of the spin is transmitted to the recording layer 17. As a result, the magnetization direction of the recording layer 17 is aligned with the same direction as the magnetization direction of the pinned layer 22-1.

  When the recording layer 17 is magnetized in the opposite direction (assuming that the above operation is a “0” write operation, in the case of a “1” write operation), the pinned layer 22-2 magnetized in the opposite direction to the pinned layer 22-1. The head 20-2 is used. Similarly, the “1” write operation can be realized by flowing electrons from the head 20-2 to the recording medium 10.

  At the time of reproducing recorded information, electrons are passed from the head toward the magnetic cell 14 so as to be equal to or less than a critical current value (current value in which the magnetization direction of the recording layer 17 changes due to the action of the spin possessed by the electrons). This is controlled by, for example, the bias circuit 30.

  Since the magnetic cell 14 is provided with the pinned layer 15 on the lower side of the recording layer 17 with the nonmagnetic layer 16 interposed therebetween, if the magnetization directions of the recording layer 17 and the pinned layer 15 are the same (parallel), the magnetic cell 14. When the magnetization direction of the recording layer 17 and the pinned layer 15 is opposite (antiparallel), the resistance value of the magnetic cell 14 increases.

  A change in voltage value (or change in current value) due to the difference in resistance value is detected by, for example, a sense amplifier (not shown) installed between the head and the bias circuit 30. The reproducing head may be a dedicated head, but the head 20-1 ("0" writing) or the head 20-2 ("1" writing) may also serve as this.

  As described above in detail, according to the present embodiment, electrons can be supplied from the head toward the recording medium in a non-contact manner, so that the contact resistance between the head and the recording medium can be eliminated. As a result, it is possible to avoid the problem that the contact resistance rides on the resistance value to be read out as noise, and further it is possible to reduce wear of the head and the recording medium. Other effects are the same as those of the first embodiment.

(Third embodiment)
In the third embodiment, the basic principle is the same as that of the second embodiment, but information is recorded by using only one head.

  FIG. 6 is a sectional view showing the structure of a recording / reproducing apparatus according to the third embodiment of the present invention. The recording / reproducing apparatus includes a recording medium 10 on which information is recorded and one head 20 that records information on the recording medium 10.

The configuration of the recording medium 10 includes, for example, a magnetic recording layer 17 made of a Pt _x Fe _(100-x) alloy (X = 30 at%) having a Curie temperature of about 272 ° C. (545 K), and a nonmagnetic layer 16 made of MgO. And a magnetization pinned layer 15 made of an Sm ₂ Co ₁₇ alloy having a Curie temperature exceeding 900 ° C. (1190 K). For example, the magnetization directions of the recording layer 17 and the pinned layer 15 are substantially perpendicular to the film surface. Needless to say, the recording layer 17 and the fixing layer 15 may be formed of multilayer films as in the second embodiment.

  When shipped from the factory, the magnetization direction of the recording layer 17 is assumed to be aligned with the magnetization direction of the pinned layer 15. That is, “1” is recorded in all the magnetic cells 14.

  The head 20 includes a conductive layer 21 to which electrons are supplied, and a magnetization fixed layer 22 provided at the tip of the conductive layer 21 and having a fixed magnetization direction. The magnetization direction of the pinned layer 22 is magnetized in a direction necessary for writing “0” in the magnetic cell 14. That is, in the present embodiment, the magnetization direction of the pinned layer 22 is opposite to that of the pinned layer 15.

  The magnetization direction of the pinned layer 22 is a direction perpendicular to the film surface, similar to the magnetic cell 14. That is, when the easy axis of the recording medium 10 (magnetic cell 14) is perpendicular to the film surface, the easy axis of the pinned layer 22 on the head side is also set perpendicular to the top surface of the recording medium 10.

  A bias circuit 30 for causing field emission from the head 20 is connected to the head 20 and the recording medium 10.

  FIG. 7 is a schematic diagram for explaining the drive unit 40 and the heating circuit 44 for driving the head 20. The drive unit 40 includes a slider 41 that moves on the upper surface of the recording medium 10 and a drive circuit 42 that controls the operation of the slider 41. As shown in FIG. 7, in this embodiment, there is one head, and there is also one drive unit that drives this head. The operation of moving the head to a desired specific position is the same as in the first embodiment. Further, the recording / reproducing apparatus includes a heating circuit 44 for heating the recording medium 10.

  The operation of the recording / reproducing apparatus configured as described above will be described. At the time of recording, the head 20 moves above the target magnetic cell, and a negative potential is supplied from the bias circuit 30 there. Further, the ground potential is supplied from the bias circuit 30 to the recording medium 10. When the write operation is completed, the second embodiment is performed until the magnetization direction of the recording layer 17 of the magnetic cell 14 is aligned with the magnetization direction of the pinned layer 22 of the head 20 ("0" write operation). It is the same as the form.

  Next, a case where “1” is written in the magnetic cell 14 will be described. As described above, the Curie temperatures of the fixed layer 15 and the recording layer 17 are set to different temperatures. That is, the fixed layer 15 has a Curie temperature higher than that of the recording layer 17. Therefore, when the recording medium 10 is heated to a temperature lower than the Curie temperature TC (pin) of the pinned layer 15 and higher than the Curie temperature TC (free) of the recording layer 17, only the magnetization of the recording layer 17 becomes a random orientation. During cooling, the magnetization direction of the recording layer 17 is aligned with the magnetization direction of the pinned layer 15 under the influence of the magnetization of the pinned layer 15 (entire batch “1” writing).

  Specifically, when the recording layer 17 is magnetized in the opposite direction (when “1” is written in the magnetic cell 14), the entire surface of the recording medium 10 or a part of the recording medium 10 divided into blocks is heated to about 300 ° C. Heat by circuit 44. Then, the recording layer 17 having a Curie temperature of less than 300 ° C. becomes random magnetization. At the time of cooling, the magnetization direction of the recording layer 17 is magnetized in the same direction as the magnetization direction of the fixed layer 15 due to the influence of the magnetization of the adjacent fixed layer 15. That is, the magnetization direction of the recording layer 17 is magnetized in a direction opposite to the magnetization direction of the pinned layer 22 of the head 20.

  Here, the magnetization direction of the pinned layer 22 of the head 20 needs to be opposite to the magnetization direction of the pinned layer 15 of the recording medium 10. Alternatively, the magnetization direction of the recording layer 17 may be aligned by applying an arbitrary external magnetic field to the recording layer 17 during heating. In this case, there is no restriction that the magnetization direction of the pinned layer 22 is opposite to the magnetization direction of the pinned layer 15.

  Further, a very narrow range of one bit unit may be heated using a laser beam or the like. FIG. 8 is a cross-sectional view showing another configuration example of the third embodiment. A laser irradiation device 45 is disposed above the recording medium 10. When the recording layer 17 is magnetized in the opposite direction (when “1” is written in the magnetic cell 14), the laser is irradiated from the laser irradiation device 45 to the recording layer 17. Thereby, the recording layer 17 is heated, and the recording layer 17 becomes a random magnetization.

  At the time of cooling, the magnetization direction of the recording layer 17 is magnetized in the same direction as the magnetization direction of the fixed layer 15 due to the influence of the magnetization of the adjacent fixed layer 15. That is, the magnetization direction of the recording layer 17 is magnetized in a direction opposite to the magnetization direction of the pinned layer 22 of the head 20. According to this method, “1” writing or erasing can be performed for each bit.

  At the time of reproduction, electrons are caused to flow from the head 20 toward the magnetic cell 14 so as to be not more than the critical current value. Information can be reproduced by detecting the difference in the resistance value of the magnetic cell 14 using, for example, a sense amplifier installed between the head 20 and the bias circuit 30.

  As described above in detail, according to the present embodiment, one head for writing one of the binary information may be prepared. Thereby, compared with the said 2nd Embodiment, the structure of a head and the circuit which drives a head can be simplified. Other effects are the same as those of the second embodiment.

(Fourth embodiment)
In the fourth embodiment, the magnetic layer is configured so that the magnetization direction is the in-film direction. Further, similarly to the third embodiment, information is recorded by using only one head.

  FIG. 9 is a sectional view showing the structure of a recording / reproducing apparatus according to the fourth embodiment of the present invention. The recording / reproducing apparatus includes a recording medium 10 on which information is recorded and one head 20 that records information on the recording medium 10.

  The pinned layer 22 of the head 20, the recording layer 17 and the pinned layer 15 of the magnetic cell 14 are each configured such that the magnetization direction is substantially in the in-plane direction. Thick arrows shown in each magnetic layer in FIG. 9 indicate the magnetization direction. About each material, it is the same as the said 2nd Embodiment.

  The operation of the recording / reproducing apparatus configured as described above will be described. At the time of recording, the head 20 is moved above the target magnetic cell. The head 20 is arranged such that the magnetization direction of the pinned layer 22 is opposite to the magnetization direction of the pinned layer 15.

Next, a negative potential is supplied to the head 20 from the bias circuit 30. Further, the ground potential is supplied from the bias circuit 30 to the recording medium 10. As a result, a potential difference is generated between the head 20 and the recording medium 10, and electrons (electron flow e ⁻ ) flow from the head 20 toward the recording medium 10 in a non-contact manner by a principle such as field emission. When the recording operation is completed, the magnetization direction of the recording layer 17 of the magnetic cell 14 is aligned with the magnetization direction of the fixed layer 22 of the head 20 (“0” writing operation).

  On the other hand, when the recording layer 17 is magnetized in the opposite direction (when “1” is written), first, the head 20 itself is rotated 180 degrees from the position for the “0” writing operation in the in-film direction. As a result, the magnetization direction of the pinned layer 22 is arranged in a direction opposite to the original magnetization direction (magnetization direction in the case of the “0” write operation) with respect to the recording layer 17.

  Thereafter, electrons are allowed to flow from the head 20 toward the recording medium 10 in a non-contact manner. Thereby, “0” can be written in the magnetic cell 14. The reproduction of recorded information is the same as in the second embodiment.

  As the recording operation, writing may be performed while rotating the head 20 for each bit, or “0” writing may be collectively performed first, and then “1” writing may be performed collectively thereafter. This depends on how much recording speed is required and how large a buffer memory can be mounted.

  As described above in detail, according to this embodiment, binary information can be recorded on a recording medium using one head. Further, the Curie temperature of the recording layer 17 and the fixed layer 15 may be normal temperature or higher, and there is no limitation on the Curie temperature as in the third embodiment. Other effects are the same as those of the second embodiment.

(Fifth embodiment)
In the fifth embodiment, a configuration example for reproducing the recorded information of the magnetic cell 14 by configuring the magnetic cell 14 only by the magnetization recording layer 17 (see the first embodiment) is shown.

  FIG. 10 is a cross-sectional view showing a configuration of a recording / reproducing apparatus according to the fifth embodiment of the present invention. The recording / reproducing apparatus includes a recording medium 10 on which information is recorded, two heads 20-1 and 20-2 that record information on the recording medium 10, and a reproducing head 50. In FIG. 10, only one head 20-1 is shown as a recording head for simplification.

  As shown in FIG. 10, the reproducing head 50 includes an MR (magnetoresistance effect) element 51. This is basically the same as the TMR or GMR read head structure of the current HDD. The MR element 51 includes a magnetization pinned layer 52 whose magnetization direction is fixed, a magnetization free layer 54 whose magnetization direction changes, and a nonmagnetic layer 53 provided between the pinned layer 52 and the free layer 54. Has been. The MR element 51 is disposed so that the film surface direction of the MR element 51 is perpendicular to the upper surface of the recording medium 10, for example.

  The material of the MR element 51 is the same as the material of the magnetic cell 14 shown in the second embodiment. The configuration of the recording medium 10 is the same as that in the first embodiment.

  The operation of the recording / reproducing apparatus configured as described above will be described. At the time of recording, the operation is the same as that described in the first embodiment.

  During reproduction, the reproduction head 50 moves above the target magnetic cell 14. When a signal magnetic field corresponding to the magnetization direction of the recording layer 17 is sensed, the resistance value of the MR element 51 in the head 50 changes. As a result, the value of the current flowing through the MR element 51 changes. This change in current value is detected by a sense amplifier or the like (not shown) connected to the reproducing head 50. Needless to say, this is the same as the reading method of the current HDD. In the reading method shown in this embodiment, a weak current can be read.

  The effect peculiar to the present embodiment is that the technical hurdle is low because the method is used in the current HDD. As described in the prior art, writing using a magnetic field is expected to be difficult, but reading using a magnetic field is expected to extend the life. As long as the read method used in the current HDD is applicable, the read method shown in this embodiment is useful.

  Needless to say, the reproducing head system described in this embodiment can be combined with the second to fourth embodiments.

  The present invention is not limited to the above-described embodiment, and can be embodied by modifying the components without departing from the scope of the invention. In addition, various inventions can be configured by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some constituent elements may be deleted from all the constituent elements disclosed in the embodiments, or constituent elements of different embodiments may be appropriately combined.

1 is a cross-sectional view showing a configuration of a recording / reproducing apparatus according to a first embodiment of the present invention. Schematic for demonstrating the drive parts 40-1 and 40-2 for driving the heads 20-1 and 20-2. Sectional drawing which shows the structure of the recording / reproducing apparatus which concerns on the 2nd Embodiment of this invention. Sectional drawing which shows the other example of the adhering layer. Sectional drawing which shows the other example of the adhering layer. Sectional drawing which shows the structure of the recording / reproducing apparatus which concerns on the 3rd Embodiment of this invention. Schematic for demonstrating the drive part 40 and the heating circuit 44 for driving the head 20. FIG. Sectional drawing which shows the other structural example of the recording / reproducing apparatus which concerns on the 3rd Embodiment of this invention. Sectional drawing which shows the structure of the recording / reproducing apparatus which concerns on the 4th Embodiment of this invention. Sectional drawing which shows the structure of the recording / reproducing apparatus which concerns on the 5th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Recording medium, 11 ... Substrate, 12 ... Insulating layer, 13 ... Protective film, 14 ... Magnetic cell, 15 ... Magnetization fixed layer, 15-2, 15-4 ... Ferromagnetic layer, 15-1 ... Antiferromagnetic layer , 15-3 ... nonmagnetic layer, 16 ... nonmagnetic layer, 17 ... magnetization recording layer, 18 ... conductive layer, 20, 20-1, 20-2 ... head, 21, 21-1, 21-2 ... conductive layer , 22, 22-1, 22-2... Magnetization fixed layer, 30... Bias circuit, 40, 40-1, 40-2 ... drive unit, 41, 41-1, 41-2 ... slider, 42, 42-1. , 42-2 ... driving circuit, 43 ... motor, 44 ... heating circuit, 45 ... laser irradiation device, 50 ... reproducing head, 51 ... MR element, 52 ... magnetization fixed layer, 53 ... nonmagnetic layer, 54 ... magnetization free layer .

Claims (9)

A recording medium including a plurality of magnetic cells in which information is recorded, including a magnetization recording layer whose magnetization direction changes;
A binary structure is provided by supplying spin-polarized electrons to the magnetic cell , which includes a first magnetization pinned layer disposed above the recording medium via a space or an insulating layer and having a magnetization direction fixed. A first head for writing one of the information ;
A binary layer is provided by supplying spin-polarized electrons to the magnetic cell, which includes a second magnetization pinned layer which is disposed above the recording medium via a space or an insulating layer and whose magnetization direction is fixed. A second head for writing the other of the information;
Comprising
The recording / reproducing apparatus according to claim 1, wherein the magnetization direction of the first magnetization pinned layer is opposite to the magnetization direction of the second magnetization pinned layer . The magnetic cell includes a third magnetization pinned layer whose magnetization direction is fixed, and a first nonmagnetic layer provided between the third magnetization pinned layer and the magnetization recording layer. The recording / reproducing apparatus according to claim 1 . The recording / reproducing apparatus according to claim 1 , wherein the magnetization direction of the magnetization recording layer is determined by the spin-polarized electrons. 4. A recording / reproducing apparatus according to claim 1 , wherein a distance between the recording medium and the head is 50 nm or less. The recording / reproducing apparatus according to claim 1 , further comprising a bias circuit that supplies a negative voltage between the head and the recording medium. 6. The recording / reproducing apparatus according to claim 1 , wherein the magnetization directions of the magnetization pinned layer and the magnetization recording layer are each perpendicular to the film surface. 3. The recording / reproducing apparatus according to claim 2 , wherein the head supplies a read current lower than a critical current that changes a magnetization direction of the magnetization recording layer to the recording medium during information reproduction. The recording apparatus according to claim 1 , further comprising a reproducing head that is disposed above the recording medium via a space or an insulating layer and that reproduces information of the magnetic cell by detecting a magnetic field generated from the magnetization recording layer. The recording / reproducing apparatus according to any one of 1 to 6 . The read head includes a fourth magnetization pinned layer whose magnetization direction is fixed, a magnetization free layer whose magnetization direction changes, and a second magnetization layer provided between the fourth magnetization pinned layer and the magnetization free layer. The recording / reproducing apparatus according to claim 8 , further comprising: a nonmagnetic layer.

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