JP2008299910A - Write-once information recording medium, information recording apparatus, and information playback apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a write-once information recording medium for enabling write protect while maintaining a high recording density same as before by a magnetic recording system. <P>SOLUTION: The write-once information recording medium 40 is provided with a substrate 41, and a recording layer 44 formed on the substrate. The recording layer is formed by a multilayer film made of metal, an alloy or a metal compound. Information is recorded by changing magnetic characteristics between a nonmagnetic state and a ferromagnetic state when a structure of the multilayer film is destroyed by irradiation with light such as near-field light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a write-once information recording medium and the like, and more particularly to a write-once information recording medium and the like particularly suitable for high-density recording.

The development of the information society is remarkable, and an apparatus capable of processing not only character information but also voice and image information at high speed is required. As one of such devices, a magnetic recording type information recording device mounted on a computer or the like is known.
In particular, in order to handle image information, a large-capacity recording apparatus is strongly demanded, and the recording density of the magnetic recording type information recording apparatus is strongly advanced. A typical magnetic recording type information recording apparatus has a plurality of information recording media rotatably mounted on a spindle.
Each information recording medium includes a substrate and a magnetic film formed thereon, and information recording is performed by forming a magnetic domain having a specific magnetization direction in the magnetic film. Currently, with the aim of higher recording density, research and development of perpendicular magnetic recording methods that record magnetization in the vertical direction from the in-plane magnetic recording method that has been recorded in the in-plane direction has been actively conducted. Practical use has also begun (for example, see Non-Patent Document 1).

An information recording apparatus using a magnetic recording system has a large capacity unlike any other, and is used for recording various data. The magnetic recording method is a rewritable recording method which is essentially infinitely rewritable since there is no physical change because the recording is performed according to the direction of magnetization.
However, some types of data, such as medical data, must be rewritten. Therefore, in order to safely store such data by the magnetic recording method, some contrivance is required, and the current state is managed by software.

  Therefore, a write-once type information recording medium is generally used for applications in which it is necessary to make rewritability essentially impossible. As the write-once information recording medium, for example, there is an optical disk using an organic dye such as DVD-R as a recording layer. This is achieved by recording and reproducing signals by utilizing the fact that the organic dye in the heated portion is decomposed by irradiating the laser to the disc to form pits and the reflectance of the laser changes. The decomposition of the organic dye is an irreversible change, and the pits once formed cannot be erased, so that it functions as a write-once information recording medium.

I Triple E Transactions on Magnetics (IEEE Trans. Magn.), 2002, 38, 1976-1978.

However, in such an optical recording system, the recording density is governed by the spot size of light. For example, even in optical recording using a blue-violet laser that is currently being actively developed and put into practical use, the recording density is approximately 30 Gbit / in ² , and a magnetic recording method that is currently in practical use is used. The recording density is only about ¼.
In addition, the current state of writing (recording) and reading (reproducing) information is slower than that of the magnetic recording method.

The present invention has been made in view of the various problems of the conventional techniques as described above. An object of the present invention is to provide a write-once information recording medium that cannot be rewritten while maintaining a high recording density equivalent to that in the conventional magnetic recording method.
Another object of the present invention is to provide an information recording apparatus capable of recording on a write-once information recording medium in which information cannot be rewritten while maintaining a writing speed equivalent to that of a conventional magnetic recording system. It is in.
Still another object of the present invention is to provide an information reproducing apparatus capable of reproducing a write-once information recording medium in which information cannot be rewritten while maintaining a reading speed equivalent to that of a conventional magnetic recording system. There is.

As a result of diligent study, the inventors of the present invention formed a minute light spot using near-field light, and irreversibly changed the structure of the medium during bit recording by this light spot, and reading was magnetoresistive. It was considered that a write-once information recording medium capable of high recording density could be constructed by using a head using an effect element. In addition, a high-speed information recording apparatus and information reproducing apparatus using this write-once information recording medium can be configured.
Therefore, as a result of examining various media structures, a new information medium structure that has a multilayer film structure and produces a difference in magnetization state when the multilayer film structure is destroyed by local heating with a heat source such as laser light is adopted. As a result, the present inventors have found that the above requirements can be satisfied, and have completed the present invention based on such knowledge. That is, the gist of the present invention is as follows.

  That is, according to the present invention, it has a substrate and a recording layer formed on the substrate, and the recording layer changes its magnetic property from non-magnetic to ferromagnetic by light irradiation, or has a magnetic property by light irradiation. A write-once information recording medium that changes from ferromagnetic to nonmagnetic is provided.

Here, the recording layer is preferably formed of a multilayer film made of a metal, an alloy or a metal compound. The structure of the multilayer film is broken by light irradiation, so that the magnetic characteristics change from nonmagnetic to ferromagnetic, or magnetic. More preferably, the characteristics change from ferromagnetic to non-magnetic.
The multilayer film is formed by a combination of any one of Mn / Al and Mn / Bi, or at least one of CrO ₂ or Fe ₃ O ₄ and V, Cr, Nb, Mo, Ru, Rh, It is still more preferable to form a combination of at least one of a single metal selected from Ta, W, Re, Ir, Pd, and Pt or an alloy of single metals.

  In addition, according to the present invention, a light irradiation unit that irradiates a write-once information recording medium with near-field light, a recording head that applies a magnetic field to perform recording, and an information recording medium drive unit that drives the write-once information recording medium; And a head drive unit for driving the recording head, and the light irradiation unit changes the magnetic characteristics of the recording layer of the write-once information recording medium from non-magnetic to ferromagnetic by irradiation with near-field light, or strengthens the magnetic characteristics. An information recording apparatus is provided in which information is recorded by changing the direction of magnetism from a magnetic layer to a non-magnetic state and aligning the magnetic direction of a portion having ferromagnetism in a recording layer.

  Here, the recording layer of the write-once information recording medium that is irradiated with near-field light by the light irradiation unit is formed of a multilayer film made of a metal, an alloy, or a metal compound, and the light irradiation unit is multilayered by irradiation with near-field light. It is preferable to change the magnetic characteristics of the write-once information recording medium from non-magnetic to ferromagnetic or change the magnetic characteristics from ferromagnetic to non-magnetic by breaking the film structure.

  Furthermore, according to the present invention, a reproducing head for reading information recorded on the write-once information recording medium, an information recording medium driving unit for driving the write-once information recording medium, a head driving unit for driving the reproducing head, And an information reproducing apparatus for reproducing information by reading a magnetic field difference between a ferromagnetic portion and a non-magnetic portion of a recording layer of a write-once information recording medium. Provided.

  According to the present invention, it is possible to obtain a write-once information recording medium that achieves a high recording density and cannot be rewritten.

  Hereinafter, the best mode for carrying out the present invention (embodiment) will be described in detail. However, the present invention is not limited to the following embodiment, and various modifications may be made within the scope of the gist of the present invention. Can be implemented.

FIG. 1 is a diagram for explaining a main part of an information recording apparatus and an information reproducing apparatus to which the present embodiment is applied.
The information recording apparatus and the information reproducing apparatus shown in FIG. 1 are a spindle section (information recording medium driving section) 11 that is rotationally driven by a motor, and a write-once information recording to which the present embodiment mounted on the spindle section 11 is applied. The head unit 12 includes a medium 40, a recording head, a reproducing head, and the like, and the head driving unit 13 that drives the head unit 12 to position the write-once information recording medium 40 on a desired track.
The write-once information recording medium 40 is rotated at a predetermined rotational speed by the spindle unit 11. The head unit 12 floats using the pressure generated by the air flow caused by the rotation of the write-once information recording medium 40. The flying height is usually about 5 nm.
The head drive unit 13 moves the head unit 12 to a predetermined position, and information is recorded and reproduced by a recording head and a reproducing head described later.
The write-once information recording medium 40 shown in FIG. 1 has been described as an example of a fixed type. However, the write-once information recording medium 40 is a cartridge type, and a plurality of write-once information recording media 40 are replaced and recorded. It may be reproducible.

FIG. 2 is a diagram illustrating the structure of the head unit 12 in the information recording apparatus to which the present embodiment is applied.
The head unit 12 shown in FIG. 2 includes a light irradiation unit 21 that irradiates near-field light and a recording head 22 that performs recording by applying a magnetic field.
As will be described in detail later, the write-once information recording medium 40 is a recording layer having a characteristic that the magnetic characteristic changes from nonmagnetic to ferromagnetic by light irradiation, or the magnetic characteristic changes from ferromagnetic to nonmagnetic by light irradiation. The magnetic characteristics change by irradiating near-field light as in this embodiment.

If the recording layer has the property that the magnetic properties change from non-magnetic to ferromagnetic by light irradiation, the portion that was irradiated with near-field light changed to ferromagnetic and the portion that was not irradiated with light , Maintain non-magnetic. Magnetism is applied to the portion changed to ferromagnetism by the recording head 22 to align the direction of magnetism in a certain direction. In this way, a bit pattern can be formed and information can be recorded.
On the other hand, when the recording layer has a characteristic that the magnetic property changes from ferromagnetic to non-magnetic by light irradiation, the portion irradiated with near-field light changes to non-magnetic and the light is not irradiated Maintains ferromagnetism. In the ferromagnetic part, a magnetic field is applied by the recording head 22 to align the magnetic direction in a certain direction. In this way, a bit pattern can be formed and information can be recorded in the same manner as described above.

It is preferable to use near-field light as the light irradiation in order to enable a recording density exceeding the diffraction limit of light and realize high-density recording. For example, it is possible to form a very small light spot of about 30 nm.
The light irradiation unit 21 that irradiates the near-field light is not particularly limited, but, for example, a general-type device that generates near-field light by irradiating a planar head with a laser is used. it can. As the recording head 22, a recording magnetic head used in a normal hard disk device or the like can be used. This magnetic head has a structure in which a coil is wound around a ring-shaped core (magnetic pole) provided with a gap in part, and the direction of magnetism can be changed by passing a write current through the coil.
The spindle unit (information recording medium driving unit) 11 and the head driving unit 13 are also the same as a hard disk device or the like which is an information recording medium of a normal magnetic recording system, and thus the information recording to which the present embodiment is applied. The device can achieve the same writing (recording) speed as a conventional hard disk device or the like.

FIG. 3 is a diagram illustrating the structure of the head unit 12 in the information reproducing apparatus to which the present embodiment is applied.
The head unit 12 shown in FIG. 3 is a reproducing head, and the magnetoresistive effect element 31 that reads information recorded on the write-once information recording medium 40, and both sides of the magnetoresistive effect element 31 are only from the part immediately below the magnetoresistive effect element 31. A magnetic shield layer 32 is provided for contributing the signal magnetic field to reproduction.
Since the magnetic field is different depending on whether it is ferromagnetic or non-magnetic, the leakage current is detected by the magnetoresistive element 31 and the difference in the magnetic field is read to read the information recorded on the write-once information recording medium 40. be able to.

As the magnetoresistive effect element 31, a magnetoresistive effect element used in a normal hard disk device or the like can be used. Among them, a reproduction signal is obtained by using a GMR film using a giant magnetoresistive effect (GMR effect). This is preferable from the viewpoint of large output.
Since reading of information is the same as that of a hard disk device that is an information recording medium of a normal magnetic recording system in this way, the information reproducing device to which this embodiment is applied reads (reproduces) the same as the hard disk device or the like Speed is feasible.
In the above example, the information recording apparatus and the information reproducing apparatus have been described as separate apparatuses. For example, the light irradiation unit 21, the recording head 22 (see FIG. 2), and the magnetoresistive effect element 31 are integrated into a head. A configuration as an information recording / reproducing apparatus provided in the unit 12 (see FIG. 1) and capable of recording and reproducing information with one apparatus is also conceivable.

Next, the write-once information recording medium 40 to which this embodiment is applied will be described in detail.
In the magnetic recording method, reading is possible even with an 850 kFCI with a linear recording density of a 30 nm bit length class by using a highly sensitive reading element using the giant magnetoresistance effect (GMR effect). This is the main reason why it is possible to increase the recording density of magnetic recording.
However, as described above, the magnetic recording method is essentially a recording method in which no physical or chemical change of a substance occurs, and thus can be rewritten infinitely in principle. Therefore, to make the write-once type, it is necessary to change the physical or chemical structure of the recording medium.

FIG. 4 is a schematic cross-sectional view of a write-once information recording medium to which the present embodiment is applied.
The write-once information recording medium 40 shown in FIG. 4 has a multilayer structure in which a substrate 41, a SiN layer 42, an Al heat sink layer 43, a recording layer 44, and a protective layer 45 are sequentially stacked. The write-once information recording medium 40 has two basic structures, a substrate 41 and a recording layer 44, but it is more preferable to provide other layers for the following reasons.

  For the substrate 41, a resin such as glass, aluminum, or polycarbonate can be used. However, it is more preferable to use a glass substrate that has a small surface roughness, is easy to perform high density recording, and is excellent in strength and hardness.

The SiN layer 42 is a layer for accumulating heat due to light irradiation such as near-field light, and the Al heat sink layer 43 is a layer for radiating heat conversely. The amount of heat transferred to the recording layer 44 can be controlled by the balance between the thicknesses of the two layers.
The protective layer 45 is a layer for protecting the recording layer 44, and carbon or the like can be used.

Further, as described above, the recording layer 44 has a characteristic that the magnetic characteristic changes from nonmagnetic to ferromagnetic by light irradiation such as near-field light, or the magnetic characteristic changes from ferromagnetic to nonmagnetic by light irradiation. .
Specifically, the recording layer is formed of a multilayer film made of a metal, an alloy, or a metal compound, and this multilayer film breaks down due to diffusion or the like due to heating by light irradiation, resulting in a change in magnetic characteristics.

Examples of the multilayer film whose magnetic characteristics change from nonmagnetic to ferromagnetic by light irradiation include those in which Mn and Al are multilayered, and those in which Mn and Bi are multilayered. In this case, the multilayer film of Mn and Al or the multilayer film of Mn and Bi is nonmagnetic. However, when heated by light irradiation, ferromagnetic MnAl alloy and MnBi alloy are formed, and the magnetic properties change to ferromagnetic.
Further, examples of the multilayer film whose magnetic characteristics change from ferromagnetic to non-magnetic upon irradiation with light include those in which CrO ₂ and Cr are multilayered, or those in which Fe ₃ O ₄ and Cr are multilayered. In this case, since CrO ₂ and Fe ₃ O ₄ are ferromagnetic, the multilayer film of CrO ₂ and Cr or the multilayer film of Fe ₃ O ₄ and Cr is ferromagnetic. However, by heating by light irradiation, the crystal structure of CrO ₂ and Fe ₃ O ₄ is broken and becomes non-magnetic.
The multilayer film whose magnetic characteristics change from ferromagnetic to non-magnetic by light irradiation is at least one of CrO ₂ or Fe ₃ O ₄ , V, Cr, Nb, Mo, Ru, Rh, Ta, W, You may form by the combination with at least 1 among the metal single-piece | unit selected from Re, Ir, Pd, and Pt, or the alloy of these metal single-piece | units.
A simple metal such as Cr or V or an alloy thereof functions as a layer for magnetically connecting the ferromagnetic layers.
Such changes are accompanied by physical and chemical changes and are irreversible. Therefore, once information is recorded, it cannot be rewritten.
Here, ferromagnetism means not only ferromagnetism but also ferrimagnetism.

  In addition, since the magnetic characteristics between ferromagnetic and non-magnetic are changed, it is easier to catch a change in the magnetic state that is smaller than other magnetic characteristics such as changes in magnetic characteristics between hard magnetism and soft magnetism. Become. For this reason, higher density is easy.

FIG. 5 is a schematic cross-sectional view of a write-once information recording medium utilizing changes in magnetic properties between hard magnetism and soft magnetism.
The write-once information recording medium 50 shown in FIG. 5 has a structure in which a substrate 51, an Fe—O layer 52, an Fe layer 53, a Pt layer 54, and a protective layer 55 are sequentially stacked.
The recording layers of the write-once information recording medium 50 are an Fe layer and a Pt layer. In this state, the recording layer exhibits soft magnetism as a magnetic characteristic. However, mutual diffusion between the two layers proceeds by heating due to light irradiation or the like, and an FePt alloy is formed. This FePt alloy exhibits hard magnetism. Since this change is irreversible, a write-once information recording medium can be manufactured by adopting the above structure. The difference from the write-once information recording medium 40 of the present embodiment is that the change in magnetic properties between ferromagnetic and non-magnetic is used essentially, or the change in magnetic properties between hard magnetism and soft magnetism is used. It is a difference of what to do.

  Hereinafter, the present invention will be described more specifically based on examples. In addition, this invention is not limited to a following example, unless it deviates from the summary.

Example 1
A write-once information recording medium having the structure shown in FIG. 4 was produced. As the substrate 41, a disc-shaped crystallized glass substrate having a diameter of 2.5 inches (6.5 cm) was used.
On the substrate 41, an SiN layer 42, an Al layer 43, and a recording layer 44 were sequentially formed. Each layer was fabricated by DC sputtering. For the SiN layer 42, a mixed gas of Ar and N ₂ was used as a sputtering gas, and for the other layers, Ar gas was used as a sputtering gas.
The thickness of each layer was 10 nm for the SiN layer 42 and 10 nm for the Al heat sink layer 43. As the recording layer 44, a multilayer film of Mn / Al was used. The thickness of each of the Mn layer and the Al layer was 1.5 nm, and the lamination period was 4 periods.
Then, a carbon protective layer having a thickness of 2 nm was formed as a protective layer 45 on the recording layer 44 by sputtering in Ar gas having a gas pressure of 0.5 Pa.

(Example 2)
Write-once information in the same manner as in Example 1 except that a CrO ₂ / Cr multilayer film is used as the recording layer 44 and the thicknesses of the CrO ₂ layer and the Cr layer are 1.5 nm and 0.5 nm, respectively. A recording medium was prepared.

(Comparative example)
A write-once information recording medium having the structure shown in FIG. 5 was produced. As the substrate 51, a disc-shaped crystallized glass substrate having a diameter of 2.5 inches (6.5 cm) was used.
On the substrate 51, an Fe—O layer 52, an Fe layer 53, and a Pt layer 54 were sequentially formed. Each layer was fabricated by DC sputtering. The Fe—O layer 52 was formed by sputtering an Fe target in a mixed gas of Ar and O ₂ , and the sputtering of the Fe layer 53 and the Pt layer 54 was performed in Ar gas. The gas pressure during sputtering of the Fe—O layer 52, the Fe layer 53, and the Pt layer 54 was 0.9 Pa.
The thickness of each layer was 3 nm for the Fe—O layer 52, and 3 nm for each of the Fe layer 53 and the Pt layer 54.
On the Pt layer 54, as a protective layer 55, a carbon protective layer was formed to a thickness of 2 nm by sputtering in Ar gas having a gas pressure of 0.5 Pa.

[Evaluation]
Next, the recording and reproducing characteristics of the write-once information recording medium were evaluated.
After applying a lubricant having a thickness of 1 nm on the protective layer of the write-once information recording media produced in Example 1, Example 2, and Comparative Example, these write-once information recording media (discs) are shown in FIG. The recording / reproduction characteristics were evaluated by mounting in the information recording apparatus and information reproducing apparatus described in FIG.
The near-field light used in the information recording apparatus was irradiated from the light irradiation unit 21 by using a semiconductor laser that generates a wavelength of 780 nm as a laser and irradiating the Planar head to generate near-field light.
In addition, the recording head 22 with a trailing shield, a trailing shield gap length Gts = 35 nm, a track width Tw = 70 nm-100 nm, and a magnetic flux density of 2.4 T was used, and a ring type head structure was adopted.
The magnetoresistive element 31 has a track width Twr = 60 nm, a reproduction gap Gs = 50 nm, and an MR (magnetoresistance) ratio = 13%, and the spin valve magnetoresistive film is formed by a pair of magnetic shield films. The one with a sandwiched structure was adopted. The magnetoresistive element 31 can detect the magnetic flux leaking from the recording bit immediately below.

Information recording is performed by fixing the laser input power to the light irradiation unit 21 at 80 mw and changing the linear recording density from 500 kFCI to 1200 kFCI. After irradiating near-field light, a magnetic field is applied in one direction by the recording head 22. Applied.
For information reproduction, the output was measured by a reproducing head. Using a spectrum analyzer, analyze the output frequency and define the output at a frequency corresponding to the recording linear recording density as carrier (C), the base value as noise (N), and the carrier-to-noise ratio as C / N ratio. The electric signal characteristics were evaluated.

FIG. 6 is a graph summarizing the relationship between the linear recording density and the C / N ratio evaluated as described above.
It can be seen that at all linear recording densities, Example 1 and Example 2 have a higher C / N ratio than the comparative example.

Further, in order to investigate the difference between the media before and after the irradiation with near-field light, a bit pattern having a bit length of 40 nm and a bit space of 80 nm was recorded, and MFM (Magnetic Force Microscopy) observation was performed.
As a result, in the case of Example 1, since a magnetic flux was generated only from the bit forming portion, an image with strong contrast was obtained. In the case of Example 2, unlike Example 1, an image was obtained in which the magnetic flux was weak in the bit forming part and the magnetic flux was observed strongly in the non-bit forming part. On the other hand, in the case of the comparative example, a magnetic flux having a strong contrast was detected in the bit forming portion, while a spot-like magnetic domain structure was observed in the non-recorded portion where the bit was not formed.

For example, in the case of Example 1, only the bit forming portion is ferromagnetic, whereas in the comparative example, the bit forming portion is hard magnetic and the bit non-forming portion is soft magnetic. it is conceivable that. That is, in the case of the comparative example, the magnetization of the bit non-forming portion is oriented in the plane, and the magnetization is randomly oriented. When this state is observed by MFM, a region (bit) in which the magnetization is directed in one direction exists in the region where the magnetization is fluctuated in the plane.
For this reason, when the linear recording density is increased, the influence of the component in which the magnetization fluctuates between bits becomes relatively strong. Therefore, in the case of the comparative example, the C / N ratio is the case of the example. It is considered to deteriorate compared to On the other hand, in Examples 1 and 2, since the difference between ferromagnetic and non-magnetic is read, it is considered that the C / N ratio is improved as compared with the comparative example.

It is a figure explaining the principal part of the information recording device and information reproducing apparatus to which this Embodiment is applied. It is a figure explaining the structure of the head part in the information recording device to which this Embodiment is applied. It is a figure explaining the structure of the head part in the information reproducing apparatus to which this Embodiment is applied. It is a schematic sectional drawing of the write-once type information recording medium to which this embodiment is applied. It is a schematic sectional drawing of the write-once information recording medium using the change of the magnetic characteristic between hard magnetism and soft magnetism. It is the figure which put together the relationship between linear recording density and C / N ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Spindle part, 12 ... Head part, 13 ... Head drive part, 21 ... Light irradiation part, 22 ... Recording head, 31 ... Magnetoresistive element, 32 ... Magnetic shield layer, 40, 50 ... Write-once information recording medium, 41, 51 ... substrate, 42 ... SiN layer, 43 ... Al heat sink layer, 44 ... recording layer, 45, 55 ... protective layer, 52 ... Fe-O layer, 53 ... Fe layer, 54 ... Pt layer

Claims (8)

A substrate,
A recording layer formed on the substrate,
The write-once information recording medium, wherein the recording layer has a magnetic property that changes from nonmagnetic to ferromagnetic when irradiated with light, or a magnetic property that changes from ferromagnetic to nonmagnetic when irradiated with light.   The write-once information recording medium according to claim 1, wherein the recording layer is formed of a multilayer film made of a metal, an alloy, or a metal compound.   The write-once type according to claim 2, wherein the structure of the multilayer film is broken by the light irradiation, so that the magnetic characteristics change from non-magnetic to ferromagnetic, or the magnetic characteristics change from ferromagnetic to non-magnetic. Information recording medium.   The write-once information recording medium according to claim 2, wherein the multilayer film is formed of any one combination of Mn / Al and Mn / Bi. The multilayer film is composed of at least one of CrO _{2 and} Fe ₃ O _{4 and} a single metal selected from V, Cr, Nb, Mo, Ru, Rh, Ta, W, Re, Ir, Pd, and Pt. 3. The write-once information recording medium according to claim 2, wherein the write-once information recording medium is formed by a combination with at least one of alloys of the single metals. A light irradiation unit for irradiating the write-once information recording medium with near-field light;
A recording head for recording by applying a magnetic field;
An information recording medium driving unit for driving the write-once information recording medium;
A head drive unit for driving the recording head,
The light irradiation unit changes the magnetic characteristics of the recording layer of the write-once information recording medium from non-magnetic to ferromagnetic by irradiation of the near-field light, or changes the magnetic characteristics from ferromagnetic to non-magnetic,
The information recording apparatus according to claim 1, wherein the recording head records information by aligning a magnetic direction of a portion having ferromagnetism in the recording layer in a certain direction. The recording layer of the write-once information recording medium irradiated with the near-field light by the light irradiation unit is formed of a multilayer film made of a metal, an alloy, or a metal compound,
The light irradiation unit changes the magnetic characteristics of the write-once information recording medium from non-magnetic to ferromagnetic, or changes the magnetic characteristics from ferromagnetic to non-magnetic by breaking the structure of the multilayer film by the irradiation of the near-field light. The information recording apparatus according to claim 6, wherein the information recording apparatus is changed to: A reproducing head for reading information recorded on a write-once information recording medium;
An information recording medium driving unit for driving the write-once information recording medium;
A head driving unit for driving the reproducing head,
The information reproducing apparatus is characterized in that the reproducing head reproduces information by reading a magnetic field difference between a ferromagnetic portion and a nonmagnetic portion of the recording layer of the write-once information recording medium.

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