JP5736664B2 - Titanium oxide particles, manufacturing method thereof, magnetic memory, optical information recording medium, and charge storage type memory - Google Patents

Description

The present invention relates to titanium oxide particles, a manufacturing method thereof, a magnetic memory, an optical information recording medium, and a charge storage type memory, and is suitable for application to, for example, an oxide containing Ti ³⁺ (hereinafter simply referred to as titanium oxide). It is a thing.

For example, Ti ₂ O ₃ is representative of the titanium oxide is a phase change material having a variety of interesting properties, for example, a metal - insulator transition and, paramagnetic - It is known that the anti-ferromagnetic transition occurs. Ti ₂ O ₃ is also known for its infrared absorption, thermoelectric effect, magnetoelectric (ME) effect, etc. In addition, in recent years, a magnetoresistive (MR) effect has also been found. Such various physical properties have been studied only in bulk bodies (˜μm size) (see, for example, Non-Patent Document 1), and the mechanism is still unclear.

Hitoshi SATO, et al., JORNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol.75, No.5, May, 2006, pp.053702 / 1-4

By the way, conventional methods for synthesizing such titanium oxide include baking in vacuum at about 1600 ° C., carbon reduction of TiO ₂ at about 700 ° C., TiO ₂ , H ₂ , TiCl ₄ at about 1000 ° C. Has been synthesized as a bulk body by firing. There has been no report of TiO _x nanoparticle (nm size) containing Ti ³⁺ so far, and the development of new physical properties is expected by making the nanoparticle.

  Therefore, the present invention has been made in consideration of the above points. Titanium oxide particles capable of exhibiting unprecedented physical properties, a method for producing the same, a magnetic memory using the same, an optical information recording medium, and charge storage The purpose is to propose a type memory.

In order to solve this problem, claim 1 of the present invention comprises a Ti ₃ O ₅ particle main body having a Ti ₃ O ₅ composition and maintaining a paramagnetic metal state in a temperature range of 0 to 800K. When the Ti ₃ O ₅ particle main body is formed, the silica glass covering the surface of the Ti ₃ O ₅ particle main body is removed, and the particle size of the Ti ₃ O ₅ particle main body is 4 to 90 nm. it is characterized in that.

According to a second aspect of the present invention, the Ti ₃ O ₅ particle main body has an orthorhombic crystal structure in a paramagnetic metal state in a temperature range of at least 500K, and the paramagnetic metal in a temperature range of at least 300K. It has a monoclinic crystal structure in a state.

Moreover, Claim 3 of this invention mixes the raw material micelle solution which has the water phase containing a titanium chloride in an oil phase, and the neutralizer micelle solution which has the water phase containing a neutralizer in an oil phase. In the prepared mixed solution, a silane compound is added to produce silica-coated titanium hydroxide compound particles in which the surface of the titanium hydroxide compound particles in the mixed solution is coated with silica, and the silica-coated titanium hydroxide compound is produced. After separating the particles from the mixed solution, the Ti ₃ O ₅ particle main body was generated in the silica glass by firing in a hydrogen atmosphere , and the silica glass was removed from the surface of the Ti ₃ O ₅ particle main body. It is characterized by this.

According to a fourth aspect of the present invention, a raw material micelle solution having an aqueous phase containing titanium chloride in an oil phase and a neutralizing micelle solution having an aqueous phase containing a neutralizing agent in the oil phase are mixed. And a step of producing titanium hydroxide compound particles in the mixed solution, and a silica coating in which a silane compound is added to the mixed solution and the surface of the titanium hydroxide compound particles is coated with silica. A step of generating titanium hydroxide compound particles, and separating the silica-coated titanium hydroxide compound particles from the mixed solution, followed by firing in a hydrogen atmosphere, thereby forming a particulate Ti ₃ O ₅ particle main body in silica glass generating a, the Ti ₃ O ₅ by removing the silica glass covering the surface of the particle body, to produce titanium oxide particles made of the Ti ₃ O ₅ particle body It is characterized in further comprising a.

Further, according to claim 5 of the present invention, in the step of generating the titanium oxide particles,
The silica glass is removed from the surface of the Ti ₃ O ₅ particle main body by at least one of potassium hydroxide ethanol solution, sodium hydroxide aqueous solution or tetramethylammonium hydroxide aqueous solution. .

A sixth aspect of the present invention includes a magnetic layer formed by fixing a magnetic material on a support, and the titanium oxide particles according to any one of the first to third aspects are used for the magnetic material. It is characterized by that.

According to a seventh aspect of the present invention, the recording light for recording is condensed on the recording layer, whereby information is recorded on the recording layer, and the reading light for reading is condensed on the recording layer. In the optical information recording medium for reproducing the information recorded in the recording layer, the recording layer has a composition of Ti ₃ O _{5 because} of the difference in reflectance of the return light returning from the recording layer . consists particulate _Ti 3 _{O 5} particle body to maintain the state of the paramagnetic metal in the temperature range of 0～800K, when forming the _Ti 3 _{O 5} particle body, the surface of the _Ti 3 _{O 5} particle body Titanium oxide particles from which the covered silica glass has been removed are used.
The eighth aspect of the present invention is characterized in that a particle diameter of the Ti ₃ O ₅ particle main body is 4 to 90 nm.

A ninth aspect of the present invention includes a charge storage layer formed by fixing a charge storage material on a support, and the charge storage material includes titanium oxide particles according to any one of the first to third aspects. Is used.

According to the first and fourth aspects of the present invention, titanium oxide particles capable of exhibiting unprecedented new physical properties can be provided.

Further, according to claim 6 of the present invention, a magnetic memory using titanium oxide particles capable of exhibiting unprecedented new physical properties as a magnetic material can be provided.

According to claim 7 of the present invention, an optical information recording medium using titanium oxide particles capable of expressing new unprecedented physical properties for the recording layer can be provided.

  Further, according to claim 9 of the present invention, a charge storage type memory using titanium oxide particles capable of expressing new unprecedented physical properties as a charge storage material can be provided.

It is a TEM image which shows the structure of the titanium oxide particle by this invention. It is a schematic diagram showing a crystal structure and _α-Ti 3 _{O 5} crystal structure of _λ-Ti 3 _{O 5.} It is a TEM image which shows the structure of the microstructure in which the titanium oxide particle by this invention is formed in the silica glass. It is the schematic where it uses for description until it produces a silica covering titanium hydroxide compound particle. It is the schematic which shows the structure of a silica covering titanium hydroxide compound particle. It is a TEM image which shows the structure of a silica covering titanium hydroxide compound particle. It is a graph which shows the analysis result of the XRD pattern of a microstructure. It is the schematic where it uses for description of the separation process which isolate | separates the titanium oxide particle formed in the silica glass from a silica glass. It is a graph which shows the analysis result of the XRD pattern of a titanium oxide particle. It is a graph which shows the relationship of the magnetic susceptibility and temperature of the conventional bulk body and the titanium oxide particle by this invention. It is a schematic view showing the crystal structure of _β-Ti 3 _{O 5.} It is a photograph which shows the change of the hue of a pellet sample when irradiating the pulse laser beam from which energy differs with respect to a pellet sample. It is the graph which showed the relationship between KM value before and after irradiating a pulse laser beam with respect to a pellet sample, and a wavelength. It is a graph with which it uses for description of the use of a titanium oxide particle. Ti ₃ O ₅ is a graph showing the phase transition of the β-phase and α-phase due to the temperature change of the single crystal. Relationship between the ratio and the temperature of the charge-delocalized unit of Ti ₃ O ₅ single crystal is a schematic diagram showing the relationship between the ratio of free energy and the charge-delocalized unit Gibbs. It is the schematic which shows the relationship between the ratio of the charge delocalization unit of the sample which consists of a lambda phase of this invention, and temperature, and the relationship between the Gibbs free energy and the ratio of a charge delocalization unit. It is a graph which shows the relationship between the free energy of Gibbs, the ratio of a charge delocalization unit, and temperature. It is a graph which shows the relationship between the temperature at the time of light irradiation, and the ratio of a charge delocalization unit. It is a photograph which shows a mode when a titanium oxide particle containing solution is dripped at a Pyrex substrate. It is a SEM image which shows the cut surface vicinity of the surface of a Pyrex substrate. It is the schematic where it uses for description when the titanium oxide particle taken out out of the silica glass is used for the recording layer of the optical information recording medium used for near-field light. It is the schematic which shows the image when the light spot used with the general optical information recording / reproducing apparatus and the light spot of near-field light are irradiated with respect to the titanium oxide particle 1 shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1) Configuration of Titanium Oxide Particles FIG. 1 is a TEM image obtained by imaging titanium oxide particles 1 with a transmission electron microscope (TEM), and a plurality of titanium oxide particles 1 are dispersed without being bonded to each other. doing. Each of the plurality of titanium oxide particles 1 has a particle size of about 8 to 14 nm, and the outer shape is a nano-size formed in the same particle shape such as a cubic shape, a spherical shape, an elliptical spherical shape, or the like. It consists of a Ti ₃ O ₅ particle body 2.

  FIG. 1 is a TEM image of the titanium oxide particles 1 obtained by classifying the manufactured titanium oxide particles 1 and having a particle size of about 8 to 14 nm. In the present invention, the particle size is about 4 to 90 nm. The titanium oxide particles 1 can also be produced. Moreover, in FIG. 1, in order to clearly understand the size and shape of each titanium oxide particle 1 in a TEM image, a titanium oxide particle is used by using a dispersion composed of tetramethyl ammonium hydroxide (TMAH). 1 is dispersed.

In practice, such a titanium oxide particle 1 has a composition of Ti ₃ O ₅ having a pseudo-brookite structure, the crystal structure can undergo phase transition by changing the temperature, and the entire temperature range (for example, 0 to 800 K). In this temperature range, it exhibits Pauli paramagnetism and can maintain a paramagnetic metal state. As a result, in the titanium oxide particles 1 according to the present invention, a conventionally known bulk body made of Ti ₃ O ₅ (hereinafter referred to as a conventional crystal) can be used even in a temperature range of less than about 460 K at which phase transition to a nonmagnetic semiconductor occurs. It has an unprecedented characteristic that it can maintain the state of a paramagnetic metal.

In practice, the titanium oxide particles 1 can be a monoclinic crystal phase (hereinafter also referred to as a λ phase) in which Ti ₃ O ₅ maintains a paramagnetic metal state in a temperature range of about 300 K or less. . The titanium oxide particles 1 begin to undergo a phase transition when the temperature exceeds about 300K, and the λ phase and the orthorhombic α-phase in the paramagnetic metal state are mixed, and the temperature exceeds about 500K. In the region, the crystal structure can be only α phase.

In this embodiment, as shown in FIG. 2A, the Ti ₃ O ₅ particle body 2 in the temperature region of about 300 K or less has a crystal structure belonging to the space group C2 / m and a lattice constant of a = 9.835 (1) Å, b = 3.994 (1) Å, c = 9.9824 (9) Å, β = 90.720 (9) °, unit cell density d = 3.988 g / cm ³ Ti ₃ O ₅ (hereinafter referred to as λ-Ti ₃ O ₅ ). On the other hand, as shown in FIG. 2B, the Ti ₃ O ₅ particle main body 2 in the temperature region of about 500 K or more has a crystal structure belonging to the space group Cmcm and a lattice constant of a = 3.798 ( 2) −, b = 9.846 (3) Å, c = 9.988 (4) Å, d = 3.977 g / cm ^{3 can} be α-Ti ₃ O ₅ .

(2) Method for Producing Titanium Oxide Particles In the present invention, first, as shown in FIG. 3, a microstructure formed by dispersing a plurality of titanium oxide particles 1 in silica glass 3 having an amorphous structure. 4 is manufactured. Thereafter, the silica glass 3 is removed from the entire surface of the Ti ₃ O ₅ particle body 2 by removing the silica glass 3 of the microstructure 4 and taking out the plurality of titanium oxide particles 1 from the silica glass 3. The fine titanium oxide particles 1 that are entirely exposed to the outside are manufactured.

  Here, first, a manufacturing method for manufacturing the microstructure 4 as shown in FIG. 3 will be described, and then a separation process for separating the titanium oxide particles 1 from the silica glass 3 of the microstructure 4 will be described.

(2-1) Manufacturing Method of Microstructure FIG. 3 is a TEM image obtained by imaging the microstructure 4 with a transmission electron microscope (TEM), and the particle size is approximately about 4 to 90 nm, for example. The aligned fine titanium oxide particles 1 are synthesized so as to be dispersed in the silica glass 3.

Thus, the microstructure 4 in which the titanium oxide particles 1 are formed in the silica glass 3 can be manufactured by combining the reverse micelle method and the sol-gel method as follows. Specifically, first, a surfactant (for example, cetyltrimethylammonium bromide (CTAB (C ₁₆ H ₃₃ N (CH ₃ ) ₃ Br))) is added to a solution having an oil phase composed of octane and 1-butanol. And titanium chloride is added and dissolved.

Thereby, as shown to FIG. 4 (A), the raw material micelle solution which has the water phase 6 containing a titanium chloride in the oil phase is produced. Here, titanium tetrachloride (TiCl ₄ ) can be applied as titanium chloride. In addition to the preparation of the raw micelle solution, a surfactant (for example, cetyltrimethylammonium bromide (CTAB (C ₁₆ H ₃₃ N (CH ₃ ) ₃ Br) is added to a solution having an oil phase composed of octane and 1-butanol. ))) Is dissolved and a neutralizing agent is mixed.

Thus, as shown in FIG. 4 (A), ammonia aqueous phase 7 containing (NH _3), to produce a neutralizer micelle solution having the oil phase. Here, an aqueous ammonia solution can be applied as the neutralizing agent. Next, the mixed micelle solution is prepared by stirring and mixing the raw micelle solution and the neutralizer micelle solution by the reverse micelle method. At this time, a hydroxylation reaction occurs in the aqueous phase, and as shown in FIGS. 4B and 4C, titanium hydroxide compound particles 10 made of Ti (OH) ₄ are generated in the aqueous phase 9 of the mixed solution. Can be done.

Next, as shown in FIG. 4D, a solution of a silane compound such as tetraethoxysilane (TEOS ((C ₂ H ₅ O) ₄ Si)) is appropriately added to the mixed solution by a sol-gel method. As a result, a hydrolysis reaction occurs in the mixed solution. For example, after 24 hours, a silica-coated titanium hydroxide compound in which the surface of the titanium hydroxide compound particles 10 is coated with silica 5 as shown in FIG. Particles 12 can be made.

Next, centrifugal separation is performed to separate the silica-coated titanium hydroxide compound particles 12 as shown in FIG. 5 from the mixed solution, followed by washing and drying, whereby silica-coated titanium hydroxide compound particles 12 (encapsulated in silica 5). Extracted Ti (OH) ₄ fine particles) from the mixed solution. A TEM image of the dried silica-coated titanium hydroxide compound particles 12 was taken with a transmission electron microscope (TEM), and a TEM image as shown in FIG. 6 was obtained. From this TEM image, it was confirmed that the silica-coated titanium hydroxide compound particles 12 were fine particles having a particle size of about 5 nm.

Subsequently, the dried silica-coated titanium hydroxide compound particles 12 (Ti (OH) ₄ fine particles coated with silica 5) are heated to a predetermined temperature (about 1060 to 1220) in a hydrogen atmosphere (0.3 to 1.5 L / min). And firing for a predetermined time (about 5 hours). This firing process, the silica-coated titanium hydroxide compound particles 12 by the oxidation reaction inside the silica shell, reducing the Ti ^4+, an oxide containing ^{_{Ti 3+ Ti 3 O 5 (Ti}} 3+ 2 Ti ⁴⁺ O ₅ ) particle bodies are produced in the silica 5.

In this way, a plurality of titanium oxide particles 1 composed of fine-particle Ti ₃ O ₅ particle main bodies having a λ phase or an α phase due to a temperature change and having a uniform particle size are dispersed in the silica glass 3. The formed microstructure 4 can be produced (FIG. 3). Incidentally, the coating with silica 5 can also serve to prevent sintering of particles.

Here, when the XRD pattern was measured about the microstructure 4 manufactured in this way, the analysis result as shown in FIG. 7 was obtained. FIG. 7 shows the diffraction angle on the horizontal axis and the diffraction X-ray intensity on the vertical axis. As shown in FIG. 7, in the XRD pattern, since a peak indicating SiO ₂ (silica) appears, it was confirmed that the microstructure 4 has the silica 5. Moreover, in the microstructure 4, portions appearing peaks in XRD patterns, since different from the _α-Ti 3 _{O 5} in the XRD pattern (not shown), the crystal structure is not the _α-Ti 3 _{O 5} I was able to confirm. Note that the microstructure 4 manufactured in this way was confirmed by elemental analysis to have a ratio of Ti ₃ O ₅ and SiO ₂ of 13: 87%, and X-ray fluorescence (XRF) analysis. Thus, it was confirmed that no impurity element was present (less than 0.1%).

(2-2) Separation process for separating the titanium oxide particles formed in the silica glass from the silica glass Next, the microstructure 4 manufactured in this way is in the form of fine particles formed in the silica glass 3. A separation process for separating and taking out the plurality of titanium oxide particles 1 from the silica glass 3 will be described below.

In this case, as shown in FIG. 8, the microstructure 4 obtained by the above-described manufacturing method is obtained by adding a potassium hydroxide ethanol solution (potassium hydroxide concentration 1 mol / dm ⁻³ ) in which potassium hydroxide is dissolved in ethanol ( (KOH / EtOH) 20, the temperature of the potassium hydroxide ethanol solution 20 is kept at about 40 to 60 ° C., and the silica glass 3 covering the entire surface of the titanium oxide particles 1 is left for about 12 hours. The titanium oxide particles 1 are removed from the surface. Thereafter, the potassium hydroxide ethanol solution 20 as an etching solution to which the microstructure 4 is added is centrifuged at 11000 rpm for about 10 minutes, and the precipitate 22 precipitated in the container 21a is recovered.

  Next, the precipitate 22 is added and dispersed in the aqueous solution 23, and then centrifuged again at 11000 rpm for about 10 minutes to recover the precipitate precipitated in the container 21b. The precipitate is washed twice with water. Wash once with ethanol.

  Subsequently, this precipitate was further washed twice with ethanol, and then dispersed in a 0.2 wt% tetramethyl ammonium hydroxide (TMAH) aqueous solution (shaking treatment 10 minutes, ultrasonic treatment 3 minutes). And classify by centrifugation at 15000 rpm for 10 minutes. Next, the titanium oxide particles 1 generated by separating from the supernatant liquid 26 in the container 21c are collected, and the separation process is completed. The titanium oxide particles 1 thus obtained were about 70% when the recovery rate was theoretically calculated from the titanium oxide content estimated in the manufacturing process of the microstructure 4.

  In the above-described embodiment, the case where the potassium hydroxide ethanol solution 20 is applied as the etching solution has been described. However, the present invention is not limited to this, and the point is that the etching solution can be used from the surface of the titanium oxide particles 1. As long as the silica glass 3 can be removed, various other etching solutions such as a sodium hydroxide aqueous solution, a tetramethylammonium hydroxide aqueous solution, or a mixed solution thereof may be applied.

For example, when a sodium hydroxide aqueous solution is used as the etching solution, the microstructure 4 is added to the sodium hydroxide aqueous solution (sodium hydroxide concentration 3 mol / dm ^-3 ), and the temperature of the sodium hydroxide aqueous solution is adjusted. The silica glass 3 covering the entire surface of the titanium oxide particles 1 could be removed from the surface of the titanium oxide particles 1 by keeping the temperature at about 50 ° C. and leaving it for about 6 hours.

When a tetramethylammonium hydroxide aqueous solution is used as an etching solution, the microstructure 4 is added to a tetramethylammonium hydroxide aqueous solution (tetramethylammonium hydroxide 1 mol / dm ^-3 ), and the tetrahydroxide hydroxide is added. The silica glass 3 covering the entire surface of the titanium oxide particles 1 could be removed from the surface of the titanium oxide particles 1 by maintaining the temperature of the methylammonium aqueous solution at about 70 ° C. and leaving it for about 48 hours.

(3) Characteristics of Titanium Oxide Particles Titanium oxide particles 1 according to the present invention produced by the manufacturing method described above have the following characteristics.

(3-1) X-ray diffraction (XRD) measurement of titanium oxide particles in a temperature range of 0 to 300K In the temperature range of 0 to 300K, the XRD of the titanium oxide particles 1 was measured. Here, FIG. 9 is an analysis result of the XRD pattern of the titanium oxide particles 1, in which the horizontal axis indicates the diffraction angle and the vertical axis indicates the diffraction X-ray intensity. As shown in FIG. 9, in XRD patterns appeared point peaks, _alpha-Ti from different than the 3 _{O 5} XRD pattern (not shown), the crystal structure is not _alpha-Ti 3 _{O 5} Was confirmed. On the other hand, in this XRD pattern, the same peak as TiO ₂ called a High-pressure phase appears in a part of the XRD pattern, and it was confirmed that the High-pressure phase TiO ₂ was expressed only by about 30%.

Here, the conventional crystal is a phase transition material as indicated by a plot point c1 shown in FIG. 10, and when the temperature is higher than about 460 K, the crystal structure becomes α-Ti ₃ O ₅ (α phase), When it is lower than about 460 K, it has been confirmed that the crystal structure becomes β-Ti ₃ O ₅ (β phase). A conventional crystal that is in a β phase in a temperature region lower than about 460K has a monoclinic crystal structure and has a Curie paramagnetism due to lattice defects near 0K and has a slight magnetization, but a temperature lower than 460K. In the region, it becomes a nonmagnetic ion and can become a nonmagnetic semiconductor.

Incidentally, the conventional crystal in the temperature region lower than about 460 K has a crystal structure belonging to the space group C2 / m as shown in FIG. 11, and the lattice constant is a = 9.748 (1) Å, b = It becomes β-Ti ₃ O ₅ consisting of 3.8013 (4) Å, c = 9.4405 (7) Å, β = 91.529 (7) °, d = 4.249 g / cm ³ . Thus, λ-Ti ₃ O ₅ is a composition of titanium oxide particles 1 in the present invention, it can be seen is different from even a β-Ti ₃ O ₅ from the crystal structure.

In addition, it has been confirmed that the conventional crystal in a very narrow temperature region near about 460 K has a crystal structure different from the α phase and the β phase, and the XRD pattern is analyzed for the crystal structure at this time. When the characteristic peak of the pattern is “●” and shown in FIG. 9, it was confirmed that it substantially coincided with the peak of the XRD pattern of λ-Ti ₃ O ₅ according to the present invention. From this, in the titanium oxide particles 1 according to the present invention, λ-Ti ₃ O _{5 that} is expressed only in a very narrow temperature range around 460 K in the conventional crystal is stably expressed in a wide temperature range of about 0 to 300 K. I understand that.

(3-2) Temperature Dependence of λ Phase and α Phase in Titanium Oxide Particles Here, the titanium oxide particles 1 of the present invention have a crystal phase of λ phase at a low temperature range in a temperature range of 0 to 650 K, and a predetermined value. The α phase begins to appear from around the temperature, and as the temperature rises, the λ phase gradually decreases and the α phase increases, then the α phase becomes larger than the λ phase, and the crystal phase becomes only the α phase at a high temperature range. . Further, even if the titanium oxide particles 1 are heated to become only the α phase, when the titanium oxide particles 1 are cooled again to a low temperature region, the λ phase is recovered, and the λ phase and the α phase are expressed depending on the temperature.

(3-3) Magnetic characteristics of titanium oxide particles Next, the magnetic characteristics of the titanium oxide particles 1 when the temperature was changed were examined. Specifically, the magnetic susceptibility of the titanium oxide particles 1 was measured using a magnetometer using a SQUID (Superconducting Quantum Interference Device). Thereby, a result like a plot point c2 shown in FIG. 10 was obtained. Including the above results, the titanium oxide particles 1 of the present invention are Pauli paramagnetic in all temperature ranges from 0 to 800 K because the crystal structure undergoes a phase transition from the λ phase to the α phase due to temperature change. It was found that the state of the magnetic metal was maintained. In the verification results of FIG. 10, it is confirmed that the titanium oxide particles 1 are Pauli paramagnetic in the entire temperature range of 0 to 600K and the state of the paramagnetic metal is maintained.

Thus, unlike the conventionally known bulk body containing Ti ³⁺ , the titanium oxide particles 1 undergo a phase transition to β-Ti ₃ O ₅ around 460 K when the temperature is lowered from a high temperature. Yuki and phase transition λ-Ti ₃ O ₅ without at all temperature ranges, was always confirmed that it is possible to maintain the α-Ti ₃ O ₅ and near the paramagnetic metal properties.

(3-4) Electrical Conductivity of Titanium Oxide Particles Further, when the crystal structure of the titanium oxide particles 1 is λ-Ti ₃ O ₅ , even if it is a semiconductor, it has an electrical resistivity close to that of a metal and has a predetermined temperature Α-Ti ₃ O ₅ expressed in the region also has substantially the same electrical resistivity as λ-Ti ₃ O ₅ .

(3-5) Pressure Effect of Titanium Oxide Particles Further, in the titanium oxide particles 1 according to the present invention, a part of the crystal structure undergoes a phase transition from the λ phase to the β phase by applying pressure. The titanium oxide particles 1 undergo a phase transition from the λ phase to the β phase even at a relatively weak pressure, and the ratio of the phase transition from the λ phase to the β phase gradually increases as the applied pressure is increased.

  In addition, when the titanium oxide particles 1 partly transformed into the β phase by applying pressure are heated to increase the temperature, the λ phase and the β phase change into the α phase in a predetermined temperature range. To do. Furthermore, when the titanium oxide particles 1 thus phase-transformed into the α phase are cooled and the temperature is lowered again, the titanium oxide particles 1 are again transformed into the λ phase. That is, the titanium oxide particles 1 according to the present invention can change the crystal structure from the λ phase to the β phase by applying pressure, and the crystal structure can be changed from the β phase to the α phase and further from the α phase by temperature change. The phase can be changed again to the λ phase.

(3-6) Light Irradiation Effect of Titanium Oxide Particles A predetermined pressure is applied to a powder sample composed of a plurality of titanium oxide particles 1 (hereinafter referred to as λ-Ti ₃ O ₅ powder sample). A disk-shaped pellet sample 30 as shown in FIG. Then, when the energy per unit area of the pulse laser beam is changed and the pulse laser beam of 532 nm is irradiated to the pellet sample 30 and the portions irradiated with the pulse laser beam are observed, it is shown in FIG. The result was obtained.

And the external appearance was compared about the pellet sample before irradiating a pulse laser beam, and the pellet sample after irradiating a pulse laser beam. As shown in FIG. 12B, the energy per unit area is 5.3 × 10 ⁻⁶ , 1.6 × 10 ⁻⁵ , 3.7 × 10 ⁻⁵ , 5.3 × 10 ⁻⁵ mJ /, respectively. When μm ² , it was confirmed that the irradiation locations ER1 ′, ER2 ′, ER3 ′, and ER4 ′ of each pulsed laser beam changed from black to brown. The irradiated spots ER1 ′, ER2 ′, ER3 ′, and ER4 ′ that turned brown were β-Ti ₃ O ₅ .

Next, the pellet sample 30 before being irradiated with the pulse laser beam and the pellet sample 30 after being irradiated with the pulse laser beam are irradiated with near-infrared light (wavelength 300 to 1500 nm) from ultraviolet light. The reflectance of the pellet sample 30 at the wavelength was measured. Then, the reflectance is applied to the Kubelka-Munk equation to calculate the KM value, and the change in the reflection spectrum of the pellet sample 30 before and after irradiation with the pulsed laser beam is verified. The result was obtained. In FIG. 13, the vertical axis represents the KM value (shown as “KM factor / au” in the figure), and the horizontal axis represents the wavelength (shown as “Wavelength / nm” in the figure). From FIG. 13, it was confirmed that the upper line is λ-Ti ₃ O ₅ having absorption over the wavelength region from ultraviolet to infrared and exhibiting a paramagnetic metallic behavior. On the other hand, it was confirmed that the lower line was consistent with β-Ti ₃ O ₅ which is a diamagnetic semiconductor.

That is, the pellet sample 30 was changed from λ-Ti ₃ O ₅ to β-Ti ₃ O ₅ when irradiated with pulsed laser light, and it was confirmed that the photo-induced phase transition occurred. As described above, it was confirmed that the titanium oxide particles 1 according to the present invention have a characteristic of undergoing a photoinduced phase transition from the λ phase to the β phase at room temperature.

(4) Operation and effect In the above configuration, according to the reverse micelle method, a raw micelle solution having an aqueous phase 6 containing titanium chloride in the oil phase is prepared, and an aqueous phase 7 containing ammonia is contained in the oil phase. A neutralizer micelle solution is prepared, and the raw material micelle solution and the neutralizer micelle solution are mixed to produce titanium hydroxide compound particles 10 made of Ti (OH) ₄ .

  Further, according to the sol-gel method, by appropriately adding a solution of the silane compound to the mixed solution, the silica-coated titanium hydroxide compound particles 12 were prepared, and after separating the silica-coated titanium hydroxide compound particles 12 from the mixed solution, By washing and drying and firing at a predetermined temperature, a microstructure 4 in which a plurality of titanium oxide particles 1 in the form of fine particles having a substantially uniform particle size are formed in silica glass 3 can be produced.

  In addition, in the manufacturing method of the present invention, such a microstructure 4 is added to the potassium hydroxide ethanol solution 20, and the temperature of the potassium hydroxide ethanol solution 20 is kept at about 50 ° C. for about 24 hours. To do. Alternatively, in place of the potassium hydroxide ethanol solution 20, the aqueous sodium hydroxide solution to which the microstructure 4 is added is kept at about 50 ° C. and left for about 6 hours. Further, instead of the potassium hydroxide ethanol solution 20, the tetramethylammonium hydroxide aqueous solution to which the microstructure 4 is added is kept at about 70 ° C. and left for about 48 hours.

  Thereby, in this manufacturing method, the silica glass 3 which covered the whole surface of the titanium oxide particle 1 can be removed from the surface of the said titanium oxide particle 1, and the titanium oxide particle 1 is isolate | separated from the silica glass 3 inside. Can be taken out. Therefore, in the present invention, it is possible to produce a plurality of titanium oxide particles 1 in the form of fine particles whose surfaces are exposed to the outside without being covered with silica glass 3 and whose particle sizes are relatively small and uniform.

Further, in this manufacturing method, since the surface of the titanium hydroxide compound particles 10 is covered with the silica 5 in the mixed solution during the manufacturing process, the silica 5 forms a small particle size of the titanium hydroxide compound particles 10. In addition, the surface of the titanium hydroxide compound particle 10 has a uniform and smooth surface with little unevenness. Thereby, in this manufacturing method, since the titanium hydroxide compound particles 10 are fired in this state, and the titanium oxide particles 1 are formed from the titanium hydroxide compound particles 10, the titanium oxide particles 1 also have a small particle size. In addition, the surface can be formed on a uniform and smooth surface with little unevenness. Therefore, in this manufacturing method, by removing the silica glass from the surface of the titanium oxide particles 1, it is possible to generate the titanium oxide particles 1 composed of the Ti ₃ O ₅ particle body 2 having a small particle size and a uniform and smooth surface. .

  And the titanium oxide particle 1 produced by such a manufacturing method becomes a λ phase in a low temperature region, an α phase in a high temperature region, and even if the temperature is lowered from a high temperature, even if the temperature becomes 460 K or less. Instead of transitioning to a β phase having the characteristics of a nonmagnetic semiconductor as in a conventional crystal, the phase transitions to a λ phase, which is a monoclinic crystal phase in which a paramagnetic metal state is maintained. Thus, the titanium oxide particles 1 according to the present invention can always maintain the characteristics of the paramagnetic metal even in a low temperature range of 460 K or less.

Thus, in the present invention, the composition of Ti ₃ O ₅ in all temperature ranges from 0 to 800 K, unlike the conventional bulk body in which the phase transitions to a nonmagnetic semiconductor and a paramagnetic metal at a temperature of about 460 K. However, it is possible to provide the titanium oxide particles 1 capable of exhibiting an unprecedented new physical property that can always maintain the characteristics of the paramagnetic metal.

Such titanium oxide particles 1 are capable of phase transition of the crystal structure of λ-Ti ₃ O _{5 to} the crystal structure of β-Ti ₃ O ₅ by applying pressure at room temperature. In addition, since the ratio of phase transition from the λ phase to the β phase gradually increases as the applied pressure is increased, the titanium oxide particles 1 have a ratio between the λ phase and the β phase by adjusting the applied pressure. Can be adjusted. Further, in this titanium oxide particle 1, even when pressure is applied and the phase transitions to the β phase, by applying heat, the β phase and the remaining λ phase are changed to the α phase in a predetermined temperature range. Phase transition can be performed. In addition, in this titanium oxide particle 1, even when the temperature is increased and the phase is changed to the α phase, the α phase can be changed again to the λ phase by cooling and lowering the temperature. .

In addition, in the titanium oxide particles 1, the crystal structure of λ-Ti ₃ O ₅ can be phase-transformed to a crystal structure composed of β-Ti ₃ O ₅ by irradiating pulsed laser light at room temperature. Even in this case, the titanium oxide particles 1 can change the λ phase and the β phase to the α phase in a temperature range of about 460 K or more by increasing the temperature by applying heat. By cooling and lowering the temperature, the α phase can be changed to the λ phase again.

  In addition, the titanium oxide particles 1 can be composed only of Ti having high safety, and since it is formed only from inexpensive Ti, the material cost can be reduced as a whole.

(5) Use of Titanium Oxide Particles Such titanium oxide particles 1 can be used for the following uses based on the optical characteristics, electrical conduction characteristics, and magnetic characteristics of the titanium oxide particles 1. As shown in FIG. 14, the titanium oxide particles 1 according to the present invention have a λ-phase crystal structure having the characteristics of a paramagnetic metal when the temperature is lower than about 460 K. For example, light, pressure, electromagnetic, By applying an external stimulus such as a magnetic field, the crystal structure can be changed to a β phase having the characteristics of a nonmagnetic semiconductor, and the magnetic characteristics can be varied.

  Here, in FIG. 14, the horizontal axis represents temperature, and the vertical axis represents any one of magnetic susceptibility, electrical conductivity, or reflectance. In the titanium oxide particles 1 in the present invention, the paramagnetic metal is maintained from the low temperature range to the high temperature range, so that the magnetic susceptibility, electrical conductivity, and reflectivity are kept relatively high from the low temperature range to the high temperature range. On the other hand, the β phase whose crystal structure has been changed by an external stimulus has the characteristics of a nonmagnetic semiconductor, and therefore has lower magnetic susceptibility, electrical conductivity, and reflectance than the α phase and λ phase. Thus, in this titanium oxide particle 1, the magnetic susceptibility, electrical conductivity, and reflectance can be changed by giving an external stimulus.

  In addition, even if the titanium oxide particles 1 are changed to the β phase by being applied with an external stimulus, the titanium oxide particles 1 are changed to an α phase crystal structure having the characteristics of a paramagnetic metal by raising the temperature. As the value is lowered, the crystal structure of the α phase can be changed again to the λ phase. Thus, the titanium oxide particles 1 can change the crystal structure from the λ phase to the β phase by an external stimulus, and can change the phase from the β phase to the α phase and from the α phase to the λ phase again by temperature change. It can be used for optical switching, a magnetic memory, a charge storage memory, an optical information recording medium, and the like using such a characteristic.

  In particular, in the titanium oxide particles 1 according to the present invention, since the surface thereof has less irregularities and the particle size is small, for example, it can be formed in advance so as to be approximately aligned with a certain size of about 8 to 14 nm, a magnetic memory, When a film is formed as a recording layer in a charge storage type memory, an optical information recording medium, etc., the unevenness of the recording surface is reduced by the amount that the particle size is small and fine and the surface has less unevenness. Therefore, it is possible to easily make the thickness of the recording layer uniform and flatten the recording surface.

  In addition, in the optical information recording medium using the titanium oxide particles 1 according to the present invention, for example, titanium oxide is used without using materials such as germanium, antimony, and tellurium used in Blu-ray discs, so that the toxicity is low. In addition, the cost can be reduced. Such an optical information recording medium will be described in detail later.

  More specifically, the titanium oxide particles 1 are externally stimulated with predetermined light at room temperature, and the crystal structure is changed from the λ phase, which is a paramagnetic metal, to the β phase, which is a nonmagnetic semiconductor, by the external stimulation. Can be used for optical switching.

  Further, the titanium oxide particles 1 are subjected to external stimulation by light, pressure, electromagnetic, or magnetic field at room temperature, and change the crystal structure from the λ phase that is a paramagnetic metal to the β phase that is a nonmagnetic semiconductor by the external stimulation. Can be used for a magnetic memory.

In practice, when used as such a magnetic memory, the titanium oxide particles 1 are used as a magnetic material, and a magnetic layer in which this magnetic material is fixed to a support is formed. When an external stimulus by light, pressure, electric field, or magnetic field is applied to the magnetic memory, the crystal structure is changed from λ-Ti ₃ O ₅ that is a paramagnetic metal to β-Ti ₃ O ₅ that is a nonmagnetic semiconductor by the external stimulus. By changing the magnetic characteristics, the magnetic characteristics are changed, and information can be recorded based on the magnetic characteristics. Thereby, in the magnetic memory, stored information can be read from, for example, a change in the reflectance of the laser light applied to the magnetic layer. Thus, a magnetic memory using the titanium oxide particles 1 as a magnetic material can be provided.

  Further, when the titanium oxide particles 1 having such electric conduction characteristics are dispersed in the insulator, the electric charges can be moved by hopping conduction or tunnel conduction by the titanium oxide particles 1. Therefore, the titanium oxide particles 1 can be used for a charge storage layer such as a floating gate of a charge storage type memory such as a flash memory. Thus, a charge storage type memory using a charge storage layer using the titanium oxide particles 1 as a charge storage material can be provided.

  Furthermore, since the titanium oxide particles 1 have magnetic properties and electrical conduction properties, the titanium oxide particles 1 have a novel magnetoelectric (ME) effect and can be used in a technique using these ME effects. The titanium oxide particles 1 can also be used for high-speed switching due to transient photocurrent due to coupling between optical characteristics and electrical conduction characteristics.

(6) Photoinduced Phase Transition Phenomenon of Microstructure Next, “(3-6) Light irradiation effect of titanium oxide particles” described above will be described in more detail. Here, a predetermined light is applied to a sample made of titanium oxide particles 1 having a λ-phase crystal structure. A portion given a predetermined light intensity by light is discolored to become a β phase.

  Next, when the sample that has become the β phase is irradiated again with predetermined light, the irradiated portion from which the light is irradiated changes from the β phase to the λ phase. Next, when the sample is again irradiated with predetermined light, the irradiated portion where the light is irradiated returns from the λ phase to the β phase again. As described above, the titanium oxide particles 1 repeatedly undergo phase transition from the λ phase to the β phase and from the β phase to the λ phase each time light is irradiated.

(7) Thermodynamic Analysis of Titanium Oxide Particles Here, in order to understand the formation mechanism of λ-Ti ₃ O ₅ , the ratio (x) of Gibbs free energy to charge delocalized units is expressed as a mean field theoretical model. It was calculated using the Slichter and Drickamer model.

Here, as shown in FIG. 15, in a conventional crystal (Ti ₃ O ₅ single crystal) in which the crystal structure is β-Ti ₃ O ₅ (β phase) when it is lower than about 460 K, the β phase and the α phase (semiconductor First-order phase transition between the charge local system (simply shown as a localized system in FIG. 15) and the charge delocalized phase system (simply shown as a non-localized system in FIG. 15). Considered a phase transition. Accordingly, the ratio (x) of charge localized units (Ti ³⁺ Ti ⁴⁺ Ti ³⁺ O ₅ ) and charge delocalized units ((Ti) ^{3 · 1/3} O ₅ ) was considered as an order parameter. . Here, the Gibbs free energy G in the phase transition between the β phase and the α phase is described as the following equation (1).

  In this case, the Gibbs free energy G of the β phase (charge localized system) is taken as the energy standard, x is the proportion of charge delocalized units, ΔH is the transition enthalpy, ΔS is the transition entropy, and R is Gas constant, γ is an interaction parameter, and T is temperature.

It has been reported that the transition enthalpy ΔH of α and β phases is approximately 13 kJ mol ⁻¹ and the transition entropy ΔS is approximately 29 J K ⁻¹ mol ⁻¹ . Next, the Gibbs free energy G was calculated using these values, and the relationship between the Gibbs free energy G, the ratio x of charge delocalized units, and the temperature was examined. As shown in FIGS. The relationship as shown in B) was confirmed.

By contrast, to calculate a plot of the Gibbs free energy G of λ-Ti ₃ O ₅ and the proportion x of charge delocalized units, an understanding of nano-sized λ-Ti ₃ O ₅ is necessary. is necessary. Here, transition enthalpy ΔH: 5 kJ mol ⁻¹ and transition entropy ΔS 11 J K ⁻¹ mol ⁻¹ in nano-sized λ-Ti ₃ O ₅ are used.

Next, using these values, the Gibbs free energy G is calculated according to the above-described equation 1, and the relationship between the Gibbs free energy G, the charge delocalized unit ratio x, and the temperature is examined. The relationship as shown in FIGS. 17A and 17B was confirmed. Here, from FIG. 17 (B), in λ-Ti ₃ O ₅ , the energy barrier between the charge localized system (mainly β phase) and the charge delocalized system (mainly α phase and λ phase) in the entire temperature range. It was confirmed that it existed between. Due to the existence of this energy barrier, λ-Ti ₃ O ₅ has improved temperature dependence of λ-Ti ₃ O ₅ , which is a nanocrystal, after transitioning to α phase and not transitioning to β phase even after the temperature is lowered. Can be explained. In order to transition from the λ phase to the β phase and from the β phase to the α phase across this energy barrier, an external stimulus such as pulse light or CW light is required as shown in FIG. 17A and 17B show that the β phase becomes a true stable phase at 460 K or less in the thermal equilibrium state.

  Based on such thermodynamic analysis, it is considered that this photo-induced phase transition was caused by phase collapse from a seemingly stable λ phase to a truly stable β phase by irradiation with a pulsed laser beam of 532 nm. be able to. Here, since the optical absorption of the λ phase is metal absorption, it is understood that ultraviolet light to near infrared light (laser light of 355 to 1064 nm) is effective for this metal-semiconductor transition.

  On the other hand, the return reaction from the α phase to the λ phase is considered to be due to the photo-thermal process. The photo-induced reverse phase transition from β phase to λ phase is caused by excitation from Ti d orbitals to other Ti d orbitals in the β phase band gap, and then transitions directly to λ phase, It was found that after being heated to α phase thermally, it was rapidly cooled to λ phase.

(8) Optical Information Recording Medium Using Titanium Oxide Particles as Recording Layer Titanium oxide particles 1 according to the present invention having a small particle size and few irregularities on the surface are crystallized from λ phase by pulsed light as shown in FIG. In addition to being able to make a phase transition to the β phase, the phase transition from the β phase to the α phase can be performed by light, and the phase can be changed again from the α phase to the λ phase as the temperature decreases. Accordingly, the titanium oxide particles 1 can be used for a recording layer of an optical information recording medium such as a CD (Compact Disc), a DVD (Digital Versatile Disc), and a Blu-ray Disc (registered trademark, hereinafter referred to as BD). . In this case, the optical information recording medium can perform three steps, ie, initialization of the recording layer, recording of information on the recording layer, and reproduction of information from the recording layer.

(8-1) Initialization of Optical Information Recording Medium The optical information recording medium initializes the entire optical information recording medium or a part thereof as a preparation for recording information. In this case, the recording layer is initialized by irradiating the optical information recording medium from one side of the recording layer with the initialization light from the initialization light source of the optical information recording / reproducing apparatus. At this time, the initialization light has sufficient energy to transition to the α phase even if the irradiated portion before the initialization light irradiation is either the β phase or the λ phase. In the recording layer, the phase is changed from the β phase to the α phase, further from the α phase to the λ phase, and from the λ phase to the α phase, and further from the α phase to the λ phase. By making all the portions irradiated with light into λ phases, the reflectance is made uniform.

  That is, in the optical information recording medium, for example, when the reflectance of the return light when irradiated with light and the code “0” or “1” are associated with each other, at this stage, a uniform code is obtained at any location of the optical information recording medium. Since it is “0” (or code “1”), no information is recorded.

(8-2) Recording of information When information is recorded on the optical information recording medium, recording light having a predetermined light intensity is condensed in the recording layer by the optical information recording / reproducing apparatus. In the optical information recording medium, when the recording light is irradiated, the crystal structure of the titanium oxide particles 1 changes in a local range centering on the target position, and the phase transition from the λ phase to the β phase occurs. The refractive index in the vicinity of the focal point (β phase) and its surroundings (λ phase) will be different. As a result, a recording mark formed by phase transition of the titanium oxide particles 1 from the λ phase to the β phase is formed on the recording layer of the optical information recording medium.

(8-3) Information Reproduction When reading information recorded on the optical information recording medium, reading light for reading having a predetermined light intensity is condensed in the recording layer from the optical information recording / reproducing apparatus. In the optical information recording medium, the return light returning from the recording layer is detected by the light receiving element of the optical information recording / reproducing apparatus, and the difference in reflectance caused by the difference in the crystal structure of the titanium oxide particles 1 (the presence or absence of the recording mark). The information recorded on the recording layer can be reproduced. The readout light used here has such a light intensity that when the recording layer is irradiated, the titanium oxide particles 1 of the recording layer are not phase-shifted from the λ phase to the β phase. Incidentally, in the above-described embodiment, the case where the recording mark is formed in the state in which the titanium oxide particles 1 are in the β phase has been described. However, the present invention is not limited thereto, and the titanium oxide particles 1 The state in which the λ phase is reached may be a state in which a recording mark is formed. Here, the recording light, the reading light, and the initialization light may have a wavelength of 355 to 1064 nm.

(9) Thin Film Synthesis Using Titanium Oxide Particles Next, as shown in FIG. 20, a solution containing titanium oxide particles in which a λ-Ti ₃ O ₅ powder sample (an aggregate of a plurality of titanium oxide particles 1) is added to water. Is immersed in a saturated potassium hydroxide solution (1: 1 mixed solvent of ethanol / water) at room temperature for 2 hours, and dropped on a Pyrex (registered trademark) substrate 35 that has been subjected to a hydrophilic treatment, and spread in this state. The titanium oxide particle-containing solution was fixed on the Pyrex substrate 35 as it was, and a λ-Ti ₃ O ₅ film 36 was formed. Then, an SEM (Scanning Electron Microscope) image was taken on the cut surface near the surface of the Pyrex substrate 35. As shown in FIG. 21, the λ-Ti ₃ O ₅ film 36 having a film thickness of about 500 nm can be formed on the surface of the Pyrex substrate 35 only by dropping a suitable amount of a solution containing titanium oxide particles on the Pyrex substrate 35. Was confirmed. Even when the λ-Ti ₃ O ₅ powder sample is used for thin film synthesis with a thin film thickness, the surface of the titanium oxide particles 1 has few irregularities, small particle diameters, and fine particles. It is possible to easily flatten the surface of the ₃ O ₅ film 26 and make the film thickness uniform.

  Here, FIG. 22 shows that the particulate titanium oxide particles 1 formed in the silica glass 3 are taken out from the silica glass 3 by the separation process, and the recording layer 40 of the optical information recording medium used for near-field light is formed. The schematic when formed with these titanium oxide particles 1 is shown.

In this case, recording / reproduction can be performed by irradiating the recording layer 40 with near-field light L1 emitted from the optical pickup 42. Here, FIG. 23 shows an image when the titanium oxide particles 1 according to the present invention shown in FIG. 1 are irradiated with a light spot S1 having a diameter of about 300 nm used in a general optical information recording / reproducing apparatus. The image when the light spot S2 having a diameter of about 20 nm of near-field light is irradiated is shown. For example, in an optical information recording medium in which a recording layer 40 is formed from a plurality of titanium oxide particles 1 having a particle size of about 25 nm, 1 Tbit inch ^-2 is realized as a recording density when near-field light is used for recording and reproduction. This is about 200 times that of a Blu-ray Disc, and the recording density can be improved as compared with the conventional case.

In addition, this invention is not limited to this embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. That is, the present invention comprises a Ti ₃ O ₅ particle main body 2 having a composition of Ti ₃ O ₅ and maintaining a paramagnetic metal state in a temperature range of 0 to 800 K. The Ti ₃ O ₅ particle main body 2 includes: Various other manufacturing methods, particle shapes, and the like may be applied as long as the titanium oxide particles 1 are made of fine particles and the entire surface is exposed to the outside.

1 titanium oxide particles 2 Ti ₃ O ₅ particle body 3 silica glass 4 microstructure 5 Silica
10 Titanium hydroxide compound particles
12 Silica-coated titanium hydroxide compound particles

Claims (9)

Having a composition of Ti ₃ O _5, consists particulate _Ti 3 _{O 5} particle body to maintain the state of the paramagnetic metal in the temperature range of 0～800K, when forming the _Ti 3 _{O 5} particle body, Silica glass covering the surface of the Ti ₃ O ₅ particle body has been removed ,
Titanium oxide particles, wherein the Ti ₃ O ₅ particle body has a particle size of 4 to 90 nm. The Ti ₃ O ₅ particle body is
2. A paramagnetic metal state orthorhombic crystal structure in a temperature region of at least 500K or higher, and a paramagnetic metal state monoclinic crystal structure in a temperature region of at least 300K or lower. Titanium oxide particles as described. In a mixed solution prepared by mixing a raw material micelle solution having an aqueous phase containing titanium chloride in the oil phase and a neutralizing micelle solution having an aqueous phase containing the neutralizing agent in the oil phase, the silane compound is contained in the mixed solution. To produce silica-coated titanium hydroxide compound particles in which the surface of the titanium hydroxide compound particles in the mixed solution is coated with silica,
After separating the silica-coated titanium hydroxide compound particles from the mixed solution, the Ti ₃ O ₅ particle main body is generated in silica glass by firing in a hydrogen atmosphere ,
The titanium oxide particles according to claim 1 or 2, wherein the silica glass is removed from the surface of the Ti ₃ O ₅ particle main body. A mixed solution is prepared by mixing a raw micelle solution having an aqueous phase containing titanium chloride in the oil phase and a neutralizing micelle solution having an aqueous phase containing the neutralizing agent in the oil phase, and the mixing Producing titanium hydroxide compound particles in solution;
Adding a silane compound into the mixed solution to produce silica-coated titanium hydroxide compound particles in which the surface of the titanium hydroxide compound particles is coated with silica; and
Separating the silica-coated titanium hydroxide compound particles from the mixed solution and then firing the mixture in a hydrogen atmosphere to produce fine Ti ₃ O ₅ particle bodies in silica glass;
By removing the silica glass covering the surface of the Ti ₃ O ₅ particle body, the titanium oxide particles characterized by comprising a step of generating titanium oxide particles made of the Ti ₃ O ₅ particle body Production method. In the step of generating the titanium oxide particles,
Ethanol solution of potassium hydroxide, of an aqueous solution of sodium hydroxide or tetramethylammonium hydroxide aqueous solution, according to claim 4, characterized in that the removal of the silica glass from the surface of the Ti ₃ O ₅ particle body by at least one kind The manufacturing method of the titanium oxide particle of description. A magnetic layer formed by fixing a magnetic material on a support;
Wherein the magnetic material, a magnetic memory, characterized in that the titanium oxide particle of any one of claims 1-3 is used. The recording light for recording is condensed on the recording layer, so that information is recorded on the recording layer, and the reading light for reading is condensed on the recording layer, so that the return is returned from the recording layer. Due to the difference in light reflectance, in the optical information recording medium for reproducing the information recorded in the recording layer,
The recording layer comprises a Ti ₃ O ₅ particle main body having a composition of Ti ₃ O ₅ and maintaining a paramagnetic metal state in a temperature range of 0 to 800 K, and the Ti ₃ O ₅ particle main body is An optical information recording medium , wherein the titanium oxide particles from which the silica glass covering the surface of the Ti ₃ O ₅ particle main body is removed when formed are used. Ti ₃ O ₅ The particle size of the particle body is 4 to 90 nm
The optical information recording medium according to claim 7. A charge storage layer formed by fixing a charge storage material on a support;
The charge storage type memory, wherein the titanium oxide particles according to any one of claims 1 to 3 are used as the charge storage material.