Dielectric reproducing device and dielectric recording / reproducing device

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric reproduction device and a dielectric recording and reproduction device that can increase reproduction speed. SOLUTION: A detection means 11 is provided so as to be able to perform a scan relative to a data recording layer 1 formed from a dielectric material, and detect the polarization state of each bit 1a of data recorded in the data recording layer 1. A heating means 12 is provided so as to be able to heat the bit 1a that is being detected to a set temperature while the detection means 11 is detecting the polarization state thereof. A reproduction means 13 is provided so as to be able to reproduce data on the basis of the polarization state of each bit 1a as detected by the detection means 11.

Description

[Technical Field]

[0001] The present invention relates to a dielectric reproducing device and a dielectric recording and reproducing device. [Background technology]

[0002] Hard disk drives using magnetic recording media have been widely used as information recording and reproducing devices that are capable of high density, large capacity, and random access. Hard disk drives are used in servers, personal computers, hard disk recorders, etc., and there is a demand for improved recording density to further increase capacity. However, the recording density of 1 Tb / inch is currently 2 When the temperature approaches 1000 ps, ​​the recorded information is disturbed by thermal agitation of the magnetic medium.

[0003] Therefore, in order to achieve high-density recording beyond this limit, heat-assisted magnetic recording (HAMR) devices have been developed (see, for example, Patent Document 1 and Non-Patent Documents 1 to 3). Heat-assisted magnetic recording devices are configured to record information in a recording section of a magnetic medium by applying a magnetic field while heating the recording section with a laser beam at the moment of recording information on the magnetic medium. Furthermore, in heat-assisted magnetic recording devices, since the recording density is determined by the size of the light spot of the laser beam, it is difficult to achieve a recording density of 1 Tb / inch. 2 In order to achieve such high recording densities, a device that uses near-field light capable of generating a minute light spot of several tens of nanometers or less has been developed (see, for example, Non-Patent Documents 4 to 9).

[0004] However, in magnetic recording devices using magnetic media, it is impossible to escape the constraints imposed by the physical principle that when the bit size is reduced, the thermal stability of the recorded bits is impaired due to exchange interaction, and even if thermally assisted magnetic recording is used, there is a limit to how high the density of magnetic recording can be. Therefore, the present inventors have proposed a dielectric recording and reproducing device using a dielectric material, which is free from exchange interaction and is expected to achieve higher density than magnetic recording (see, for example, Patent Document 2 or Non-Patent Document 10). The dielectric recording and reproducing device can record and reproduce information on a dielectric material using SNDM (Scanning Nonlinear Dielectric Microscopy) technology, and is equipped with, for example, a metal probe that records data on the dielectric material, a recording signal generating means that generates a recording signal corresponding to the data, an application means that applies the recording signal between the probe and an electrode provided on the back surface of the recording layer made of the dielectric material, an AC signal generating means that generates an AC voltage signal, a voltage application means that applies an AC voltage signal between the probe and an electrode provided on the back surface of the recording layer during reproduction, an oscillation means that oscillates in accordance with the polarization state recorded in the dielectric material, a demodulation means that demodulates the oscillation signal generated by the oscillation means, and a data reproduction means that reproduces data based on the phase information of the signal demodulated by the demodulation means.

[0005] In order to realize a high-density dielectric recording and reproducing device, the present inventors have conducted basic research into recording information on dielectric materials, and have succeeded in forming domain dots with a diameter of 2.8 nm on the surface of a dielectric material (LiTaO3 single crystal) capable of recording information (see, for example, Non-Patent Document 11). This size corresponds to 80 Tb / inch 2 This corresponds to a writing speed of 2 Gbps, which is expected to lead to higher density data recording. We have also confirmed that nano-domain dots can be formed (polarization inversion) on the surface of a dielectric material (LiTaO3 single crystal) using a pulse with a pulse width of 0.5 nsec (see, for example, Non-Patent Document 11). This corresponds to a writing speed of 2 Gbps, which is expected to lead to higher recording speeds.

[0006] Based on these results, the inventors actually fabricated a prototype dielectric recording and reproducing device and performed an experiment using SNDM technology to record 64 x 64 bits of actual data onto a dielectric material (LiTaO3 single crystal). The bit spacing of the recorded data was 12.8 nm, resulting in a data rate of approximately 4 Tb / inch. 2 (See, for example, Non-Patent Document 12.) In addition, a prototype hard disk drive-type dielectric recording and reproducing device was fabricated, and recording (writing) and reproducing (reading) experiments were carried out on the surface of a disk-shaped dielectric material (LiTaO3 single crystal). The bit spacing of the recorded data was 13.7 nm, and the recording density was approximately 3.4 Tb / inch. 2 On the other hand, the read speed was 2 Mbps, and the signal-to-noise ratio (SN ratio) of the read signal to noise was 8.96 dB (see, for example, Non-Patent Document 13).

[0007] The inventors have found that when the temperature of a ferroelectric material is increased, the nonlinear dielectric constant (ε 333 Therefore, in order to further improve the reproduction speed, we have found that the nonlinear dielectric constant (ε 333 We are currently developing ferroelectric materials with the following properties (see, for example, Non-Patent Document 14).

[0008] Furthermore, the inventors of the present invention have found that when a dielectric material made of LiTaO3 single crystal with domain dots formed on its surface is heat-treated, the domain dots shrink. They have therefore derived an empirical formula that shows the relationship between the shrinkage rate of the domain dot diameter, the temperature, and the heating time. They have shown that the lifespan of an 80 nm thick LiTaO3 single crystal (the time it takes for the domain dot diameter to shrink from 50 nm to 40 nm) is more than 16 years at 80°C, which is sufficiently practical (see, for example, Non-Patent Document 15). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-133602 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-127489 [Non-patent literature]

[0010] [Non-Patent Document 1] Akira Kikitsu, et al., “A concept of exchange-coupled recording medium for heat-assisted magnetic recording”, J. Appl. Phys., 2005, 97, 10P701 [Non-patent document 2] Koji Matsumoto, Takuya Uemura, Satoshi Shimokawa, "Thermal Assisted Magnetic Recording", FUJITSU, 2007 01, 58, 1, pp.85-89 [Non-patent document 3] Tsuyoshi Yuzawa, Nobuyuki Takahashi, "Simulation Technology for Thermally Assisted Magnetic Recording Media," Fuji Jiho, 2009, Vol. 82, No. 3, pp. 170-173 [Non-patent document 4] T. Matsumoto, et al., “Highly efficient probe with a wedge-shaped metallic plate for high density near-field optical recording”, 2004, J. Appl. Phys., 2004, 95, p.3901-3906 [Non-Patent Document 5] T. Matsumoto, et al., “Thermally assisted magnetic recording on a bit-patterned medium by using a near-field optical head with a beaked metallic plate”, Appl. Phys. Lett., 2008, 93, 031108 [Non-patent document 6] WA Challener, et al., “Hear-assisted magnetic recording by a near-field transducer with efficient optical energy transfer”, Nature Photonics, April 2009, Vol.3, p.220-224 [Non-Patent Document 7] Barry C. Stipe, et al., “Magnetic recording at 1.5 Pbm-2 using an integrated plasmonic antenna”, Nature Photonics, July 2010, Vol.4, p.484-488 [Non-patent document 8] T. Matsumoto, et al., “Integrated head design using a nanobeak antenna for thermally assisted magnetic recording”, Optics Express, 13 August 2012, Vol.20, No.17, p.18946-18954 [Non-Patent Document 9] Takuya Matsumoto, "Application of near-field light to thermally assisted magnetic recording," Optics, 2013, Vol. 42, No. 1, pp. 26-31 [Non-Patent Document 10] Yasuo Naga, "Scanning Nonlinear Dielectric Microscope", Applied Physics, 1998, Vol. 67, No. 3, pp. 327-331 [Non-Patent Document 11] K. Tanaka, et al., “Scanning Nonlinear Dielectric Microscopy Nano-Science and Technology for Next Generation High Density Ferroelectric Data Storage”, Jpn. J. Appl. Phys., 2008, Vol.47, No.5, p.3311-3325 [Non-Patent Document 12] K. Tanaka and Y. Cho, “Actual information storage with a recording density of 4 Tbit / in.2 in a ferroelectric recording medium”, Appl. Phys. Lett., 2010, 97, 092901 [Non-Patent Document 13] Y. Hiranaga, T. Uda, Y. Kurihashi, H. Tochishita, M. Kadota and Y. Cho, “Nanodomain Formation on Ferroelectrics and Development of Hard-Disk-Drive-Type Ferroelectric Data Storage Devices”, Jpn. J. Appl. Phys., 2009, Vol.48, 09KA18 [Non-Patent Document 14] Y. Hiranaga and Y. Cho, “Material Design Strategy for Enhancement of Readback Signal Intensity in Ferroelectric Probe Data Storage”, IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL, March 2021, Vol.68, No.3, p.859-864 [Non-Patent Document 15] Nozomi Odagawa and Yasuo Cho, “Long-term-retention characteristics of small inverted dots formed on congruent single-crystal LiTaO3”, Applied Physics Letters, 2006, 89, 102906 Summary of the Invention [Problem to be solved by the invention]

[0011] The dielectric recording and reproducing devices described in Patent Document 2 and Non-Patent Documents 10 to 13 are expected to enable higher density data recording than magnetic recording devices using magnetic media. However, the reproduction speed of recorded data is on the order of Mbps, and there is a problem that the reproduction speed needs to be improved for practical use.

[0012] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a dielectric reproducing device and a dielectric recording and reproducing device that can improve the reproducing speed. [Means for solving the problem]

[0013] Based on the knowledge that when the temperature of a ferroelectric material is increased, the nonlinear dielectric constant increases rapidly as the temperature approaches the Curie point, the inventors have previously tried to develop ferroelectric materials with large nonlinear dielectric constants by controlling the Curie point in order to further improve the reproduction speed. However, rather than developing such new materials, the inventors have come up with the idea that the nonlinear dielectric constant can also be increased by bringing the temperature of an existing ferroelectric material closer to the Curie point, thereby arriving at the present invention.

[0014] That is, in order to achieve the above object, the dielectric reproducing device according to the present invention is a dielectric reproducing device for reproducing data recorded on a data recording layer made of a dielectric material, wherein the data recording layer is capable of recording data by the polarization state of each bit formed on the dielectric material, and the data recording layer is scanned relatively to record the polarization state of each bit corresponding to the data. Nonlinear dielectric constant due to a detecting means for detecting the polarization state of the polarized light; The nonlinear dielectric constant a heating means for heating the bit to be detected to a predetermined temperature while detecting the polarization state of each bit detected by the detecting means; The nonlinear dielectric constant and a reproduction means provided to be able to reproduce the data based on the above.

[0015] The dielectric reproducing device according to the present invention, when detecting the polarization state of each bit formed on a data recording layer made of a dielectric material by scanning the detecting means relative to the data recording layer, can raise the temperature of the bit to be detected by the heating means. This increases the nonlinear dielectric constant of each bit, making it possible to detect a reproduced signal with a high S / N ratio. When the S / N ratio of the reproduced signal is high, the reproduced signal can be detected even if the relative scanning speed of the detecting means is increased, thereby improving the reproduction speed of data recorded on the data recording layer.

[0016] In the dielectric reproducing device according to the present invention, the dielectric material may be any material that can be polarized for each individual bit, and is particularly preferably made of a ferroelectric material such as LiTaO3 crystal, e.g., CLT or SLT. Furthermore, in the dielectric reproducing device according to the present invention, the detecting means may be arranged to scan relative to the data recording layer, and during scanning, the data recording layer may be fixed and the detecting means may move, or the detecting means may be fixed and the data recording layer may move, or the detecting means and the data recording layer may move together.

[0017] In the dielectric reproducing device according to the present invention, the higher the nonlinear dielectric constant of the bit to be detected by the detecting means, the more the reproduction speed can be improved. Therefore, the temperature of the bit should be lower than the Curie point of the dielectric material forming the data recording layer, and the closer to the Curie point, the better. Therefore, it is preferable that the temperature of each bit heated by the heating means be as close as possible to the Curie point of the dielectric material forming the data recording layer. Since the Curie point varies depending on the dielectric material, it is preferable to set the heating temperature by the heating means according to the type of dielectric material forming the data recording layer. For example, the Curie point is 601°C for CLT and 685°C for SLT.

[0018] In the dielectric reproducing device according to the present invention, the data recording layer is made of a dielectric material, and therefore heating reduces the retention characteristics of each bit. Therefore, in order to prevent a reduction in the thermal stability of the data recording layer, it is preferable that the heating means be capable of heating only the bit being detected to a predetermined temperature only while the detection means is detecting the polarization state. However, it is also possible to heat not only the bit being detected but also the surrounding bits for the short time it takes for the detection means to detect the polarization state. It is preferable that the heating means be configured to heat the bit being detected in synchronization with the timing at which the detection means detects the polarization state of the bit being detected.

[0019] Furthermore, in the dielectric reproducing device according to the present invention, the heating means may be configured in any way to heat the bit to be detected. For example, the heating means may have an emission means for emitting laser light and a lens for focusing the laser light emitted from the emission means, and may be configured to irradiate the bit to be detected with the laser light focused by the lens to heat it. In this case, the temperature of not only the bit to be detected but also the surrounding bits may increase, but this has almost no effect on the thermal stability of those bits if it is only for the short time required to detect the polarization state. Therefore, the heating means can be configured with a simpler structure and at lower cost than one that heats only the bit to be detected.

[0020] The detecting means may have a probe that can be scanned relative to the data recording layer and is configured to detect the polarization state of the bit when the tip of the probe moves relative to the bit to be detected. The heating means may be capable of generating near-field light, be arranged near the probe so as to be movable together with the probe, and be configured to heat the bit to be detected using the near-field light. The detecting means may have a metal probe, and the heating means may be capable of generating near-field light by irradiating the tip of the probe with laser light and be configured to heat the bit to be detected using the near-field light. In these cases, near-field light can generate a tiny light spot of several tens of nanometers or less, so even tiny bits of data recorded at high density on the data recording layer can be heated bit by bit by increasing the temperature of each bit and detecting a reproduction signal with a high signal-to-noise ratio. Furthermore, by using near-field light, the bit to be detected can be instantaneously heated. Therefore, the bit to be detected is heated only while the detection means is detecting the polarization state, and the temperature of the bit can be reduced to the temperature before heating the moment the detection ends, thereby further improving the effect of preventing a decrease in thermal stability. Note that the data recorded at high density in the data recording layer may be recorded by any method, for example, it may be recorded by applying a voltage pulse between the probe and the lower electrode of the data recording layer, or it may be recorded by other high-density recording means.

[0021] Furthermore, in the dielectric reproducing device according to the present invention, it is preferable that the heating means is capable of scanning relatively with respect to the data recording layer and heating the bits detected by the detecting means to a predetermined temperature. In this case, the heating means may intermittently heat each bit of the data recording layer in sequence in accordance with the timing of detection by the detecting means, or may heat each bit in sequence by continuously heating the data recording layer while scanning relatively with respect to the data recording layer. Therefore, when the heating means uses light such as laser light or near-field light for heating, the heating means may use pulsed light or continuous light.

[0022] Furthermore, in the dielectric reproducing device according to the present invention, the data recording layer is preferably opaque to laser light or near-field light so that it absorbs and heats the laser light or near-field light. However, if the data recording layer is transparent to laser light or near-field light, it is not able to absorb these lights, and therefore a light absorbing layer is preferably provided on the side of the data recording layer opposite the side scanned by the detection means. Alternatively, when heating each bit with laser light, the laser light preferably has a wavelength shorter than the absorption edge of the dielectric material, and when heating each bit with near-field light, the near-field light preferably has a wavelength shorter than the absorption edge of the dielectric material. As a result, the data recording layer can efficiently absorb the laser light or near-field light used for heating, even without a light absorbing layer.

[0023] The dielectric recording and reproducing device of the present invention comprises the dielectric reproducing device of the present invention and a recording means configured to record data on the data recording layer, and is characterized in that the dielectric reproducing device is capable of reproducing the data recorded by the recording means.

[0024] The dielectric recording and reproducing device according to the present invention has the dielectric reproducing device according to the present invention, and therefore can improve the reproducing speed of data recorded on the data recording layer. 2 It is preferable that data can be recorded on the data recording layer at a high density equal to or higher than this. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide a dielectric reproducing device and a dielectric recording and reproducing device that can improve the reproducing speed. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic side view showing a dielectric regenerating device according to an embodiment of the present invention in use; [Figure 2] 1 is a side view showing a specific configuration of a dielectric regenerating device according to an embodiment of the present invention. [Figure 3] FIG. 1 is a side view showing a specific configuration of a first modified example of a dielectric regenerating device according to an embodiment of the present invention, which uses near-field light. [Figure 4] FIG. 10 is an enlarged side view of the vicinity of the probe, showing a second modified example of the dielectric regenerating device according to the embodiment of the present invention, which uses near-field light. [Figure 5] 10 is a graph showing the relationship between the nonlinear dielectric constant (ε333) of CLT and SLT and temperature in the dielectric regenerating device according to the embodiment of the present invention. [Figure 6] FIG. 10 is a perspective view showing a third modified example of the dielectric reproducing device according to the embodiment of the present invention, which reproduces a disk-shaped data recording layer. [Figure 7] FIG. 1A is a cross-sectional view showing the recording medium used in a data reproduction experiment of a dielectric reproduction device according to an embodiment of the present invention; and FIG. 1B is a graph showing the time variation of the intensity (Relative Signal Strength) of the irradiated laser light and the reproduction signal, showing the results of the data reproduction experiment. [Figure 8] 10 is a graph showing the relationship between the number of times of irradiation with laser light or the like and the pulse width when a reduction of 1% and 10% is allowed as a bit reduction rate in the dielectric reproducing device according to the embodiment of the present invention. [Figure 9] 10 is a perspective view showing the irradiation area of ​​the laser light in the case where the laser light of the heating means of the dielectric reproducing device according to the embodiment of the present invention is not only directed to the bit to be detected but also extends to the surrounding bits. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 9 show a dielectric reproducing device according to an embodiment of the present invention. As shown in Figure 1, the dielectric reproducing device 10 is a dielectric reproducing device for reproducing data recorded on a data recording layer 1 made of a dielectric material, and includes a detection means 11, a heating means 12, a reproducing means 13, and an AC voltage application means (not shown).

[0028] The data recording layer 1 is provided so that data can be recorded depending on the polarization state of each bit 1a formed in the dielectric material. Specifically, the data recording layer 1 is capable of recording data depending on whether the polarization direction of each bit 1a in the dielectric material is positive or negative. The dielectric material may be any material that can be polarized for each individual bit 1a, and is, for example, made of a ferroelectric material such as LiTaO3 crystal, e.g., CLT or SLT.

[0029] 2, the detection means 11 has a probe 11a that is provided so as to be capable of scanning relatively to the data recording layer 1 on which data is recorded, and an oscillation means 11b that oscillates in response to the polarization state of the bit 1a detected on the data recording layer 1. In the specific example shown in Fig. 2, the probe 11a and the oscillation means 11b are made up of an SNDM probe, and the oscillation means 11b is made up of an LC oscillator.

[0030] The detection means 11 is configured to detect the polarization state of the bit 1a when the tip of the probe 11a moves relatively to a position facing the bit 1a to be detected. Specifically, the sign of the nonlinear permittivity of the odd-order tensor of the dielectric material changes depending on whether the polarization direction of the dielectric material is positive or negative. When an electric field is applied to this dielectric material, the sign of the change in capacitance of the dielectric material changes due to the nonlinearity, corresponding to the positive or negative polarization. Therefore, the detection means 11 applies a known AC voltage to the data recording layer 1 using the AC voltage application means, generates a frequency-modulated signal from the capacitance of each bit 1a of the data recording layer 1 using the oscillation means 11b, outputs the signal as an oscillation signal, and detects the polarization direction of each bit 1a by comparing the frequency change with the phase of the applied AC voltage.

[0031] As shown in Figure 2, heating means 12 has emitting means 12a that emits laser light and lens 12b that focuses the laser light emitted from the emitting means. The emitting means is made of a laser diode. Heating means 12 is configured so that the tip of probe 11a moves relatively to a position facing bit 1a to be detected, and in synchronization with the timing at which detecting means 11 detects the polarization state of bit 1a, heating means 12 irradiates bit 1a with laser light 12c focused by lens 12b to heat it to a predetermined temperature only while detecting means 11 is detecting the polarization state of bit 1a.

[0032] 3, the heating means 12 may include a laser diode 21a, a near-field light generating device 21b configured to generate near-field light 21d by laser light from the laser diode 21a, and an optical waveguide 21c that guides the laser light from the laser diode 21a to the near-field light generating device 21b. In this case, the heating means 12 is preferably configured such that the near-field light generating device 21b is disposed near the tip of the probe 11a and is movable together with the probe 11a. This allows the heating means 12 to generate near-field light 21d in close proximity to the tip of the probe 11a. Furthermore, the heating means 12 is preferably configured such that the tip of the probe 11a moves relatively to a position facing the bit 1a to be detected, and the heating means 12 irradiates the bit 1a with near-field light 21d to heat it to a predetermined temperature only while the detecting means 11 detects the polarization state of the bit 1a, in synchronization with the timing at which the detecting means 11 detects the polarization state of the bit 1a.

[0033] 4, the probe 11a may be made of metal, and the heating means 12 may be configured to generate near-field light 21d by irradiating the tip of the probe 11a with focused laser light 12c, and to heat the bit 1a to be detected to a predetermined temperature by the near-field light 21d.

[0034] 1 to 3, the reproducing means 13 is provided so as to be able to reproduce data recorded on the data recording layer 1 based on the polarization state of each bit 1a detected by the detecting means 11. The reproducing means 13 includes, for example, means for demodulating the oscillation signal output by the oscillating means 11b, and means for recognizing the polarization direction of each bit 1a from the demodulated signal and reproducing the data. The AC voltage applying means is provided so as to apply a known AC voltage to the data recording layer 1, and is configured so as to be able to determine the polarization direction of each bit 1a based on whether the phase of the applied AC voltage is in phase or opposite to the phase of the demodulated signal.

[0035] The detecting means 11, reproducing means 13 and AC voltage applying means of the dielectric reproducing device 10 may be any means as long as they can detect each bit 1a by relatively scanning the data recording layer 1 and reproduce data. In a specific example shown in Fig. 2, the detecting means 11, reproducing means 13 and AC voltage applying means are made up of devices that utilize SNDM technology, such as the dielectric reproducing device described in Patent Document 2.

[0036] Next, the operation will be described. When the dielectric reproducing device 10 detects the polarization state of each bit 1a formed on the data recording layer 1 made of a dielectric material by scanning the detecting means 11 relatively to the data recording layer 1, the heating means 12 can raise the temperature of the bit 1a to be detected by the detecting means 11. This increases the nonlinear dielectric constant of the bit 1a to be detected, making it possible to detect a reproduced signal with a high S / N ratio. When the S / N ratio of the reproduced signal is high, the reproduced signal can be detected even if the relative scanning speed of the detecting means 11 is increased, thereby improving the reproduction speed of data recorded on the data recording layer 1.

[0037] In the dielectric reproducing device 10, the higher the nonlinear dielectric constant of the bit 1a to be detected by the detecting means 11, the more the reproduction speed can be improved. Therefore, the temperature of the bit 1a should be lower than the Curie point of the dielectric material forming the data recording layer 1, and the closer to the Curie point, the better. Since the Curie point varies depending on the dielectric material, it is preferable to set the heating temperature by the heating means 12 depending on the type of dielectric material forming the data recording layer 1. For example, it is preferable to heat the bit 1a to be detected by the heating means 12 to a temperature that is 100°C lower than the Curie point of the dielectric material but less than the Curie point. More specifically, when CLT is used as the dielectric material, it is preferable to heat to a temperature of 501°C or higher but lower than 601°C, and when SLT is used, it is preferable to heat to a temperature of 585°C or higher but lower than 685°C.

[0038] Here, the nonlinear dielectric constants (ε 333 The results of an experiment to investigate the relationship between the nonlinear permittivity (ε ) and temperature are shown in Figure 5. 333 ) and the nonlinear dielectric constant (ε 333 As shown in Figure 5, when the temperature of each dielectric is increased, the nonlinear dielectric constant (ε 333 ) rapidly increases. 333 is (Tc-T) -3.5 (where Tc is the Curie temperature). ε 333 is also proportional to the regeneration speed, so for example, in the case of CLT, the regeneration speed at 501°C is 472 times that at room temperature. In Non-Patent Document 13, the regeneration speed at room temperature is 2 Mbps, so the regeneration speed at 501°C for CLT is estimated to be approximately 945 Mbps.

[0039] As shown in Figure 2, the dielectric reproducing device 10 heats each bit 1a using a laser beam 12c focused by a lens 12b. When heating minute bits 1a of data recorded at high density on the data recording layer 1, the heat generated by the focused laser beam 12c may increase the temperature of not only the bit 1a being detected but also the surrounding bits 1a. However, because heating is performed only for the short time required to detect the polarization state, there is almost no effect on the thermal stability of those bits 1a. Therefore, the heating means 12 can be constructed more simply and inexpensively than one that heats only the bit 1a being detected.

[0040] 3 and 4, when near-field light 21d is used to heat each bit 1a, even for tiny bits 1a of data recorded at high density on the data recording layer 1, the temperature of each bit 1a can be increased to detect a reproduction signal with a high S / N ratio. Furthermore, by using near-field light 21d, it is possible to instantaneously heat only the bit 1a to be detected. Therefore, the bit 1a to be detected is heated only while the detection means 11 is detecting the polarization state, and the temperature of that bit 1a can be reduced to the temperature before heating the moment the detection is completed, thereby preventing a decrease in the thermal stability of the data recording layer 1.

[0041] Furthermore, in the dielectric reproducing device 10, the data recording layer 1 may be transparent to the laser light 12c shown in Fig. 2 or the near-field light 21d shown in Figs. 3 and 4, and may have a light absorbing layer on the side of the data recording layer 1 opposite to the side relatively scanned by the detecting means 11. Furthermore, the laser light 12c shown in Fig. 2 or the near-field light 21d shown in Figs. 3 and 4 may have a wavelength shorter than the absorption edge of the dielectric material. This allows the laser light 12c or the near-field light 21d to be efficiently absorbed by the data recording layer 1 even without a light absorbing layer.

[0042] Furthermore, the dielectric reproducing device 10 may be incorporated into a dielectric recording and reproducing device as a reproducing device of the dielectric recording and reproducing device. The dielectric recording and reproducing device preferably has, for example, a recording means configured to record data on the data recording layer 1, and is configured so that the data recorded by the recording means can be reproduced by the dielectric reproducing device 10. In this case, the recording means may be configured to record data on the data recording layer 1 by applying a pulse voltage between the probe 11a of the dielectric reproducing device 10 and the lower electrode of the data recording layer 1, or may be configured to record data at high density by other methods. The recording means may have a recording capacity of, for example, 1 Tb / inch 2 It is preferable that data can be recorded at the above-mentioned high density on the data recording layer 1. This makes it possible to provide a dielectric recording and reproducing device capable of high-density recording and high-speed reproduction.

[0043] The dielectric regenerating device 10 can be applied to a material in which the detected physical quantity changes with temperature, a material in which the detected physical quantity is temperature-dependent and increases as the temperature approaches the Curie point, and a material in which the detected physical quantity is temperature-dependent and increases with temperature changes.

[0044] 6, the dielectric reproducing device 10 may be configured to reproduce data from a disk-shaped recording medium 2. The recording medium 2 has a disk-shaped data recording layer 1 provided on a disk-shaped lower electrode 3, and is rotated around the central axis of the disk by a spindle motor 5. The data recording layer 1 has a plurality of bits 1a regularly arranged at predetermined intervals along the circumferential direction. The detecting means 11 and the heating means 12 are fixed at least with respect to the circumferential direction of the data recording layer 1, and are configured to scan relatively with respect to the data recording layer 1 rotated by the spindle motor 5. The heating means 12 is configured to continuously irradiate it with a laser beam 12c.

[0045] In this case, the dielectric reproducing device 10 rotates the recording medium 2 with the spindle motor 5 and heats the data recording layer 1 by continuously irradiating it with laser light 12c with the heating means 12, thereby successively heating each of the bits 1a arranged in the circumferential direction of the data recording layer 1, and the detecting means 11 can sequentially detect the polarization state of each of the bits 1a heated by the heating means 12. Also in this case, the bit 1a to be detected and its surrounding bits 1a are heated only for a short time to detect the polarization state, so there is almost no effect on the thermal stability of those bits 1a. [Example]

[0046] An experiment to reproduce (read) data from a data recording layer 1 was carried out using a dielectric reproducing device 10 shown in Figure 2. The recording medium 2 used in the experiment is shown in Figure 7(a). As shown in Figure 7(a), the recording medium 2 comprises a data recording layer 1, a lower electrode 3, and a substrate 4. In the recording medium 2, the lower electrode 3 is provided on the substrate 4, and the data recording layer 1 is provided on the lower electrode 3. The data recording layer 1 is made of CLT and has a thickness of 170 nm. The lower electrode 3 is an electrode for applying an AC voltage to the data recording layer 1, and is made of chromium and has a thickness of 500 nm.

[0047] In the experiment, laser light 12c, emitted from emitting means 12a and focused by lens 12b, was irradiated onto the surface of data recording layer 1 at a predetermined frequency to heat it. Furthermore, the signal at the irradiated position was continuously detected by detection means 11. The temporal changes in the intensity (Relative Signal Strength) of the irradiated laser light 12c and the playback signal (detection signal) are shown in Figure 7(b). As shown in Figure 7(b), it was confirmed that the intensity of the playback signal increases rapidly when the laser light 12c is irradiated and decreases rapidly when the irradiation of the laser light 12c is stopped. This indicates that it is possible to detect a playback signal with a high S / N ratio by increasing the temperature of the position (bit 1a) of the data recording layer 1 to be detected. This also indicates that the playback speed of data recorded on the data recording layer 1 can be improved.

[0048] [Evaluation of bit instability in data recording layer due to light irradiation] As shown in Non-Patent Document 15, when a dielectric material is heat-treated, the domain dots shrink. Therefore, the instability of the bits 1a in the data recording layer 1 when heated by periodically irradiating them with laser light or the like was evaluated. From the empirical formula obtained in Non-Patent Document 15, which shows the relationship between the shrinkage rate of the domain dot diameter, the temperature, and the heating time, it is found that when the data recording layer 1 is made of CLT and has a thickness of 80 nm, the shrinkage rate (r final When the laser beam or the like can be periodically irradiated when the laser beam (r / r0) is determined, the number of times n can be expressed by the following equation (1):

[0049]

number

[0050] When the data recording layer 1 is made of CLT and has a thickness of 80 nm, the relationship between the number of irradiations n of laser light or the like and the pulse width t1 when the heating temperature T is set to 550°C is calculated from equation (1) and shown in Figure 8. Figure 8 also shows the bit reduction rate (r final The results for the case where a 1% reduction is allowed (dashed line in the figure) and the case where a 10% reduction is allowed (solid line in the figure) are shown for the temperature (r0). Note that, referring to Figure 5, T = 550°C corresponds to a read speed equivalent to 4.99 Gbps.

[0051] As shown in Figure 8, if irradiation is possible up to 1 million times, and a 1% reduction is allowed, the pulse width will be approximately 10 -5 sec (10 μsec) or less. In this case, the recording density is 4 Tb / inch. 2When reproducing data with a bit interval of 12.8 nm at 1 Gbps, it can be seen that the one-dimensional spread of the laser light or the like (in the data reading direction) when the laser light or the like irradiates only one recording track may be 128 μm or less. From this result, it can be said that the light irradiated for heating does not necessarily have to be near-field light, and it may be focused laser light.

[0052] Next, as shown in FIG. 6, evaluation was performed on the case where the laser light is continuous light and spreads not only to the detected bit 1a but also to the surrounding bits 1a. For simplicity, as shown in FIG. 9, the irradiation area of the laser light is set as a square with side x, and the size of each bit 1a is set as a square with side d (d < x). Also, it is assumed that the data recording layer 1 moves one-dimensionally at a speed v along the direction of one side of each bit 1a.

[0053] Let the number of irradiations possible when heating only one bit 1a be y, the reading speed by the detection means 11 be s (bps), and the time during which the laser light irradiates one bit 1a (the same as the laser pulse width when irradiating a laser pulse to the stationary data recording layer 1) be t1 (sec). Then, the number of bits 1a irradiated with the laser light simultaneously is x / d, and further, x = d·s·t1. Let the number of irradiations possible of the laser light at this time be Z. Then, Z = y / (x / d) = y / (s·t1), and Z does not depend on the length d of one side of each bit.

[0054] Here, referring to the case where a 10% reduction shown in FIG. 8 is allowed, when s = 1 Gbps, t1 = 1 μsec, and y = 10 8 then, the number of irradiations possible Z of the laser light is Z = 10 8 / 10 9 / 10 -6 = 10 5 and 100,000 rewritings are possible. This is the same number of rewritings as that of a commercially available flash memory. Also, the irradiation area of the laser light at this time is such that when the recording density is 4 Tb / inch 2 (d = 12.8 nm), then x = d·s·t1 = 12.8×10 -9 ·109 10 -6 = 12.8 μm. This result also shows that the light irradiated for heating does not necessarily have to be near-field light, and may be focused laser light. [Explanation of symbols]

[0055] 1 Data recording layer 1a bit 10 Dielectric regeneration device 11. Detection Methods 11a Probe 11b Oscillation means 12 Heating means 12a Emission means 12b lens 12c Focused laser light 13 Regeneration means 21a Laser Diode 21b Near-field light generator 21c optical waveguide 21d Near-field light 2. Recording media 3 Lower electrode 4 boards 5 Spindle motor

Claims

1. A dielectric reproducing device for reproducing data recorded on a data recording layer made of a dielectric material, comprising: the data recording layer is capable of recording data by the polarization state of each bit formed in the dielectric material; a detecting means for detecting a nonlinear dielectric constant depending on a polarization state of each bit corresponding to the data by relatively scanning the data recording layer; a heating means for heating a bit to be detected to a predetermined temperature while the detecting means detects the nonlinear dielectric constant according to the polarization state; a reproducing means for reproducing the data based on the nonlinear dielectric constant due to the polarization state of each bit detected by the detecting means; A dielectric regenerating device comprising:

2. The heating means is configured to heat the bit in synchronization with the timing at which the detecting means detects the nonlinear dielectric constant depending on the polarization state of the bit to be detected.

2. The dielectric regenerating device according to claim 1.

3. The dielectric regenerating device according to claim 1 or 2, characterized in that the heating means has an emission means for emitting laser light and a lens for focusing the laser light emitted from the emission means, and is configured to irradiate the laser light focused by the lens onto the bit to be detected to heat it.

4. the detecting means has a probe provided so as to be capable of scanning relatively to the data recording layer, and is configured to detect the nonlinear dielectric constant depending on the polarization state of the bit when the tip of the probe moves relatively to a position facing the bit to be detected, The heating means is capable of generating near-field light, is arranged in the vicinity of the probe so as to be movable together with the probe, and is configured to be able to heat the bit to be detected by the near-field light.

3. A dielectric regenerating device according to claim 1 or 2.

5. the detecting means has a metal probe provided so as to be capable of scanning relatively to the data recording layer, and is configured to detect the nonlinear dielectric constant depending on the polarization state of the bit when the tip of the probe moves relatively to a position facing the bit to be detected, The heating means is provided so as to be capable of generating near-field light by irradiating the tip of the probe with laser light, and is configured so as to be able to heat the bit to be detected by the near-field light.

3. A dielectric regenerating device according to claim 1 or 2.

6. a light absorbing layer provided on the data recording layer opposite to the side relatively scanned by the detecting means; The data recording layer is transparent to the laser beam.

4. The dielectric regenerating device according to claim 3.

7. 4. The dielectric reproducing device according to claim 3, wherein the laser light has a wavelength shorter than the absorption edge of the dielectric material.

8. a light absorbing layer provided on the data recording layer opposite to the side relatively scanned by the detecting means; The data recording layer is transparent to the near-field light.

5. The dielectric regenerating device according to claim 4.

9. 5. A dielectric regenerating device according to claim 4, wherein the near-field light has a wavelength shorter than the absorption edge of the dielectric material.

10. 3. The dielectric reproducing device according to claim 1, wherein the dielectric material is a ferroelectric material.

11. a dielectric regenerating device according to claim 1 or 2; a recording means configured to record data on the data recording layer, The dielectric reproducing device is capable of reproducing the data recorded by the recording means. A dielectric recording and reproducing device characterized by the above.

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