JP5317065B2 - Lead-free magnetic optical element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a lead-free magnetic optical element suitable for application in the field of information communication technology such as optical isolators and high-density magneto-optical recording, and a method for manufacturing the same. Regarding technology.

  Due to the rapid spread of the Internet, there is an increasing demand for high-speed and high-capacity optical communication networks. In the future, drastic cost reduction of various optical components will be necessary in order to widely spread optical communication networks to general households and to continuously develop an advanced information communication society in the future. Among these optical components, the magneto-optical element is difficult to mass-produce and makes the entire system expensive. A magneto-optic element is an optical component that is indispensable for high-speed optical networks, and is used as an optical isolator that uses the polarization plane rotation phenomenon (Faraday rotation), which is an inherent property of the magneto-optic effect, to limit the traveling direction of light in one direction. The In current optical communication systems, a large number of optical isolators using magnetic garnet crystals (rare earth iron garnet) are arranged in laser light sources and optical amplifiers.

However, existing magneto-optical materials cannot be used in the short wavelength region of 1 μm or less, and it is difficult to integrate with other semiconductor optical components, and lead oxide of flux used for crystal growth remains. There was a problem such as.
For this reason, it cannot cope with ultra-high capacity wavelength division multiplexing communication, which will increase in importance in the future in terms of function, cost, and environment, and is the biggest issue in the development of optical communication systems.
In particular, the inclusion of lead is currently a serious environmental problem, and in July 2006, the European Union decided to eliminate lead contained in electrical and electronic equipment as a substance subject to environmental regulations under the RoHS Directive. However, for optical isolators built into communication devices, there is currently no alternative material, and as an exceptional measure, the lead content standard is being regulated to 1000 ppm or less, but in the future, replacement with non-lead materials will be promoted. It is desired.

As a next-generation key technology that solves these problems, the development of lead-free ferromagnetic semiconductors that have excellent magneto-optical effects at room temperature and the fusion of nanotechnology are attracting attention. If these technological integrations are realized, all the functions that magnetic materials are good at, such as magnetic recording and light polarization control, will be realized with lead-free semiconductor materials, and integrated with semiconductor optical components. This is also possible.
As one means, recently, the present inventors have alternately stacked Co-substituted titania nanosheets and Fe-substituted titania nanosheets by a self-assembly reaction using a nanomaterial as a basic block and a low-cost room temperature solution process, If a multilayer film or a superlattice using Co—Fe interaction is produced, the world's best magneto-optic effect that responds from the ultraviolet light to the visible wavelength region (260-500 nm) and far surpasses existing magneto-optic materials ( It has been found that it is possible to produce a magneto-optical element having 300,000 degrees / cm) (WO 2007/069638).

  An element composed of a magnetic semiconductor nanosheet is optimal for use in the ultraviolet to visible wavelength region (260-500 nm), but can be used for a semiconductor laser or the like from visible light to near infrared wavelength region (500-900 nm). The element which responds by is needed. Moreover, in order to realize the excellent magneto-optical properties of the magnetic semiconductor nanosheet, it was necessary to form a superlattice in which different nanosheets were precisely and alternately laminated so that the interlayer interaction between magnetic metals functions. Therefore, in order to manufacture a low-cost and simple magneto-optical element, it has been desired to develop a magnetic semiconductor nanomaterial that responds to a wide wavelength region from ultraviolet light to near infrared light as a single unit.

  The present invention solves the problems of conventional magneto-optical materials from the background as described above, and is a lead-free magnetic optical element having a high magneto-optical effect in a wide wavelength region from ultraviolet light to near infrared light as a single unit. It is an object to provide a manufacturing method thereof.

  As a result of intensive research in order to solve the above problems, the present inventors have found that a single layer of a layered titanium oxide in which two or more different magnetic elements are simultaneously substituted at a titanium lattice position is obtained. By making magnetic nanothin films using substituted titania nanosheets as a basic block, it is possible to control optical transitions between different magnetic metals through spin interaction, and by using these optical transitions, ultraviolet The present inventors have found that a high magneto-optical effect and its control are possible in a wide wavelength range from 1 to the near infrared, and have completed the present invention based on these technical findings.

  That is, the lead-free magneto-optical element of the present invention is, firstly, a magnetic element simultaneous substitution titania nanosheet obtained by exfoliating a layered titanium oxide in which two or more different magnetic elements are simultaneously substituted at a titanium lattice position. It is characterized by using a magnetic nano thin film made of

Second, in the lead-free magnetic optical element of the first invention, the magnetic nano-thin magnetic element simultaneous substitution titania nanosheet has a composition formula of Ti _1-xy M _x M ′ _y O ₂ (where M Is a magnetic metal selected from V, Cr, Mn, Fe, Co, Ni, Cu, M ′ is at least one magnetic metal other than M selected from V, Cr, Mn, Fe, Co, Ni, Cu, It is characterized by 0 <x + y <1).

  Third, in the lead-free magnetic optical element of the second invention, the magnetic element simultaneous substitution titania nanosheet of the magnetic nano thin film is such that M and M ′ are the same element, and the valences of M and M ′ are mutually It is characterized by being different.

Fourth, in the lead-free magnetic optical element of the first invention, the magnetic nano-thin magnetic element simultaneous substitution titania nanosheet has a composition formula of Ti _1-xy Co _x Fe _y O ₂ (where 0 < It is characterized by x + y <1).

  The fifth is the lead-free magnetic optical element according to any one of the first to fourth aspects, wherein the magnetic nano thin film includes a magnetic element simultaneous substitution titania nanosheet, an organic polymer, an inorganic polymer, a metal complex, or polynuclear hydration. It is characterized in that it is a thin film in which at least one thin film of an inorganic compound containing a physical ion is combined.

  6th is the manufacturing method of the lead-free magnetic optical element according to any one of the first to 5th inventions, wherein a single layer of layered titanium oxide in which two or more different magnetic elements are simultaneously substituted at a titanium lattice position. A magnetic element simultaneous substitution titania nanosheet obtained by peeling is laminated on a substrate through an organic polycation as a cationic substance to form the magnetic nanothin film.

  Seventh, in the method for producing a lead-free magnetic optical element according to the sixth invention, a magnetic nano thin film is formed by spin-coating or dip-coating a magnetic element simultaneous substitution titania nanosheet on a substrate. .

According to the first invention, a magnetic nano thin film exhibiting a high magneto-optical effect in a wide wavelength region from ultraviolet light to near infrared light is realized, and advanced control of characteristics is possible. Furthermore, such a magnetic nano thin film can be manufactured at low cost using a lead-free safe material.
The magnetic nano thin film of the present invention realizes a high-performance optical integrated circuit that is integrated with low-cost, high-performance optical isolators, semiconductor lasers, and various optical components for high-speed optical networks that are expected to have higher performance in the future. Therefore, it can contribute to the further spread of the Internet and the development of a ubiquitous society based on advanced information communication. In addition to optical isolators, devices using the magneto-optical effect have a wide range of applications such as magneto-optical recording elements, magneto-optical sensors, and optical switches. Therefore, magnetic devices having excellent magneto-optical characteristics provided by the present invention are provided. Nano thin films are extremely useful when applied to these technical fields.

  According to the second invention, in the semiconducting titania nanosheet, it is possible to impart unique magnetic interaction and electronic transition between different 3d transition metal elements, and in a wide wavelength region from ultraviolet light to near infrared light. Fabrication of magnetic nano-thin films exhibiting a high magneto-optic effect and free control of properties have become possible.

  According to the third invention, in the semiconducting titania nanosheet, it is possible to impart a unique magnetic interaction and electronic transition between transition metal elements having different valences, and a wide range from ultraviolet light to near infrared light. Fabrication of magnetic nano-thin films exhibiting high magneto-optic effect in the wavelength region and free control of properties are now possible.

  According to the fourth aspect of the invention, in the semiconducting titania nanosheet, the Co—Fe electronic transition is expressed through the strong electron-spin interaction of Co—Fe in the two-dimensional nanostructure, and is close to the ultraviolet light. Fabrication of magnetic nano-thin films exhibiting a high magneto-optic effect in a wide wavelength range up to infrared light and improvement of the magneto-optical properties were realized.

  According to the fifth invention, since it is possible to fuse with a polymer material such as an organic polymer, it is possible to fabricate an organic-inorganic hybrid device using the excellent magneto-optical properties of the magnetic element simultaneous substitution titania nanosheet, And it can be used as a magneto-optical element fused with molecular electronics.

  According to the sixth invention, it is possible to design a multi-layered high-quality magnetic nano thin film using a magnetic element simultaneous substitution titania nanosheet, so that a magneto-optical element having a desired film thickness and magneto-optical characteristics can be designed and manufactured. It became.

  According to the seventh invention, a low-cost, low-environment process that does not require a large vacuum apparatus or an expensive film forming apparatus, which is the mainstream of the conventional magneto-optic thin film process, can be realized.

FIG. 1 is a structural schematic diagram of a Co and Fe co-substituted titania nanosheet and its multilayer film. FIG. 2 shows a multilayer film (Ti _0.75 Co _0.15 Fe _0.1 O ₂ ) in which 10 layers of Co and Fe co-substituted titania nanosheets and polydiallyldimethylammonium chloride (PDDA) are alternately laminated on a quartz glass substrate. ) ₁₀ shows the ultraviolet / visible absorption spectrum, and the inset is an optical photograph. FIG. 3 shows a multilayer film (Ti _0.75 Co _0.15 Fe _0.1 O ₂ ) in which 10 layers of Co and Fe co-substituted titania nanosheets and polydiallyldimethylammonium chloride (PDDA) are alternately laminated on a quartz glass substrate. FIG. ₁₀ is a diagram showing magneto-optical hysteresis characteristics at room temperature and 500 nm in FIG. FIG. 4 shows a Co-substituted titania nanosheet multilayer film (a), an Fe-substituted titania nanosheet multilayer film (a), and a Co and Fe co-substituted titanium oxide nanosheet multilayer film (Ti _0.75 Co _0.15 Fe _0. is a diagram showing a magneto-optical spectrum at room temperature in _{1 O 2) 10 (b)} . FIG. 5 shows Co and Fe co-substituted titania nanosheets of different compositions (Ti _0.65 Co _0.05 Fe _0.3 O ₂ , Ti _0.7 Co _0.1 Fe _0.2 O ₂ , Ti _0.75 Co it is a diagram showing a magneto-optical spectra at room temperature of the multilayer film of _0.15 Fe _0.1 O _2). FIG. 6 is a diagram showing a crystal structure model of the Co and Fe simultaneous substitution titania nanosheet used in the first principle calculation. Co assessed by first-principles calculation, a diagram showing the electronic band structure of Fe simultaneous substitution titania nanosheet _{(Ti 0.5 Co 0.5 Fe 0.5 O} 2), (a) is _Ti 0.5 _{Co 0. The} density of states from all atoms constituting ₅ Fe _0.5 O ₂ , (b) shows the partial density of states from the magnetic element components Co and Fe of Ti _0.5 Co _0.5 Fe _0.5 O ₂ . FIG. 8 is a diagram showing optical absorption characteristics of Co and Fe co-substituted titania nanosheets (Ti _0.5 Co _0.5 Fe _0.5 O ₂ ) evaluated by the first principle calculation. FIG. 9 shows the figure of merit and response wavelength of the magneto-optical rotation angle per unit thickness in the Co and Fe co-substituted titania nanosheet multilayer film (Ti _0.75 Co _0.15 Fe _0.1 O ₂ ) ₁₀ of the present invention. FIG. For comparison, the figure of merit and maximum response wavelength of magneto-optical rotation angle per unit thickness are shown for Co, Fe-substituted titania nanosheet multilayer film, Co, Fe-substituted titania nanosheet superlattice, and typical isolator materials. . FIG. 10 shows room temperature in a multilayer film of Co and Mn co-substituted titania nanosheets (Ti _0.75 Co _0.15 Mn _0.1 O ₂ , Ti _0.775 Co _0.175 Mn _0.05 O ₂ ) having different compositions. It is a figure which shows the magneto-optical spectrum in.

  The lead-free magnetic optical element and the manufacturing method thereof according to the present invention will be described in more detail with specific examples.

FIG. 1 is a diagram schematically illustrating the structure of a magnetic nanothin film composed of a magnetic element simultaneous substitution titania nanosheet according to an embodiment of the present invention. In FIG. 1, reference numeral 1 indicates, for example, a quartz glass or Si substrate (hereinafter, simply referred to as “substrate”), 2 indicates a polymer formed on the substrate, and 3 indicates a magnetic co-substituted titania nanosheet. Yes.
In the embodiment of FIG. 1, the magnetic element simultaneous substitution titania nanosheet 3 is illustrated as being laminated.
In the present invention, the substrate 1 is not limited to quartz glass or Si substrate, but may be other types of substrates such as plastic, and a metal electrode such as gold or platinum is provided on the substrate. Similarly, a magnetic element simultaneous substitution titania nanosheet may be disposed on the resultant structure.

Magnetic element simultaneous substitution titania nanosheet (for example, Ti _0.65 Co _0.05 Fe _0.3 O ₂ , Ti _0.7 Co _0.1 Fe _0.2 O ₂ , Ti _{0. 75} Co _0.15 Fe _0.1 O ₂ ) has a two-dimensional anisotropy obtained by peeling a layered titanium compound to one layer which is a basic minimum unit of a crystal structure by a soft chemical treatment. It is a magnetic semiconductor nanomaterial.
The magnetic nano thin film of the present invention is mainly composed of such a magnetic element simultaneous substitution titania nanosheet or a laminate thereof. Here, for example, the nanosheet preferably has a thickness of about 1 nm and a lateral size of 200 nm to 100 μm. It may have a particle size.

The magnetic element simultaneous substitution titania nanosheet consists of a nanosheet obtained by exfoliating a single layer of layered titanium oxide with two or more different magnetic elements simultaneously substituted at the titanium lattice position. May be various types, for example, preferably, a titania nanosheet in which two or more 3d magnetic metal elements are simultaneously substituted at the titanium lattice position, composition formula Ti _1-xy M _x M ′ _y O ₂ (however, , M is a magnetic metal selected from V, Cr, Mn, Fe, Co, Ni, Cu, and M ′ is a magnetic metal other than M selected from V, Cr, Mn, Fe, Co, Ni, Cu. Seed, 0 <x + y <1).

  The treatment for single layer peeling can be called soft chemical treatment, and the soft chemical treatment is a treatment combining acid treatment and colloidalization treatment. That is, when titanium oxide powder having a layered structure is contacted with an acid aqueous solution such as hydrochloric acid, and the product is filtered, washed, and dried, all alkali metal ions present between the layers before the treatment are replaced with hydrogen ions. A hydrogen-type substance is obtained. Next, when the obtained hydrogen-type substance is placed in an aqueous solution of amine or the like and stirred, it is colloidalized. At this time, the layers constituting the layered structure are peeled up one by one. The film thickness can be controlled in the range of sub nm to nm.

According to the present invention, a lead-free magnetic optical element including the above method as at least a part of the process and a method for manufacturing the same are realized. For example, in the forms shown in the following examples, lead-free magnetic optical elements based on titania nanosheets simultaneously substituted with Co and Fe and titania nanosheets simultaneously substituted with Co and Mn are manufactured.
Needless to say, the present invention is not limited to the following examples.

In this example, titania nanosheets (Ti _0.65 Co _0.05 Fe ₀ ) obtained by simultaneously substituting different magnetic elements (Co, Fe) at a concentration of 5% to 30% at the titanium lattice position of the titania nanosheet that is semiconducting. _.3 O ₂ , Ti _0.7 Co _0.1 Fe _0.2 O ₂ , Ti _0.75 Co _0.15 Fe _0.1 O ₂ ), as shown in FIG. A multilayer film was produced on a Si substrate by an alternating self-assembled lamination technique via a cationic polymer (polydiallyldimethylammonium chloride (PDDA)).

  This substrate lamination technique corresponds to the alternating self-organization lamination technique disclosed in the method for producing an ultrathin titania thin film (Japanese Patent No. 3513589) invented by the present inventors. As an actual operation, a series of operations of (1) immersing the substrate in titania sol solution → (2) cleaning with pure water → (3) immersing in organic polycation solution → (4) cleaning with pure water as one cycle This is repeated as many times as necessary. As the organic polycation, polydiallyldimethylammonium chloride (hereinafter also referred to as PDDA), polyethyleneimine (PEI), polyallylamine hydrochloride (PAH) and the like are suitable. In addition, when alternating layers are stacked, there is basically no problem if a positive charge can be introduced to the substrate surface. Instead of an organic polymer, an inorganic polymer having a positive charge and an inorganic compound containing polynuclear hydrate ions are used. You can also.

  In film formation based on alternating lamination, it is sufficient that the substrate surface is sufficiently adsorbed and coated with nanosheets or polymers, and spin coating or dip coating may be used instead of the alternating self-organization lamination technique. Is possible.

The magnetic nanothin film thus prepared has a high stacking order, and shows a clear X-ray diffraction peak based on the repetition period of the magnetic element simultaneous substitution titania nanosheet and PDDA. In fact, when the formation process of the multilayer film of magnetic element simultaneous substitution titania nanosheet and PDDA was monitored by X-ray diffraction measurement, a Bragg peak showing a periodic structure around 1.4 nm appeared, and the intensity increased as the number of adsorption increased. .
That is, it is shown that the nanosheets and PDDA adsorbed and accumulated in order maintain an orderly multilayered nanostructure without being disturbed after film formation. More direct film forming process monitoring methods include measurement of film thickness by ultraviolet / visible absorption spectrum and ellipsometry. It can be seen that the film thickness gradually increases in the sub-nm to μm range for each adsorption operation. That is, the film thickness can be controlled in such an extremely fine region.

  As described above, in the present invention, the magnetic element simultaneous substitution titania nanosheet and the organic polycation are each adsorbed in a monolayer in a self-organized manner from the liquid phase, and film formation is performed by repeating this process. The film forming processing has features such as a very fine film thickness control in the range and a high degree of freedom in selecting and controlling the film composition and structure. In particular, the film thickness accuracy of multilayer ultrathin films composed of titania nanosheets and organic polycations is 1 nm or less, and the final film thickness depends on the number of repetitions of the adsorption cycle and can be increased to the μm level. is there.

FIG. 2 shows an ultraviolet / visible absorption spectrum of a multilayer film (Ti _0.75 Co _0.15 Fe _0.1 O ₂ ) ₁₀ in which 10 layers of Co and Fe co-substituted titania nanosheets and PDDA are alternately laminated on a quartz glass substrate. And optical photos. The Co and Fe co-substituted titania nanosheet has a wide band gap (300 nm) due to the quantum size effect, and the sample produced on the quartz glass substrate is as shown in FIG. It was transparent.

FIG. 3 shows a magnetic circular dichroism (MCD) magneto-optical measurement at room temperature of a multilayer film in which 10 layers of Co and Fe co-substituted titania nanosheets (Ti _0.75 Co _0.15 Fe _0.1 O ₂ ) are laminated. The obtained magneto-optical rotation angle. The magneto-optical hysteresis characteristic shown in FIG. 3 shows a difference in reflectance between right circular polarization and left circular polarization due to magnetization or spin polarization when light is reflected by a magnetic material. Corresponding to the interaction, it demonstrates the existence of magnetization. As a result of magneto-optical measurement at 500 nm in the visible light region, a multilayer film in which 10 layers of Co and Fe co-substituted titania nanosheets (Ti _0.75 Co _0.15 Fe _0.1 O ₂ ) are laminated has a unique magneto-optical response. It was confirmed that it functions as a ferromagnetic material at room temperature, and the magneto-optical figure of merit was a large value of about 130,000 degrees / cm. Similar ferromagnetic magneto-optical responses are obtained for Co and Fe co-substituted titanium oxide nanosheets with different compositions (Ti _0.65 Co _0.05 Fe _0.3 O ₂ , Ti _0.7 Co _0.1 Fe _0.2. It was confirmed even in a multilayer film in which 10 layers of O ₂ ) were laminated. As described above, as shown in FIGS. 2 and 3, it is concluded that the Co and Fe co-substituted titania nanosheet is a room temperature / ferromagnetic semiconductor that maintains transparency in the visible light region and functions as a ferromagnetic material at room temperature. Is done.

FIG. 4 shows a Co-substituted titania nanosheet multilayer film (a), an Fe-substituted titania nanosheet multilayer film (a), and a Co and Fe co-substituted titania nanosheet multilayer film (Ti _0.75 Co _0.15 Fe _0.1 ) of the present invention. O ₂₎ is a magneto-optical spectrum of the ₁₀ (b). A magnetic optical rotation angle was detected by applying a magnetic field of ± 10 kOe at each wavelength at room temperature, and the spectrum was obtained.
As shown in FIG. 4 (a), the Co-substituted titania nanosheet multilayer film and the Fe-substituted titania nanosheet multilayer film have a response in the ultraviolet region, and each showed a unique magneto-optical effect of about 10,000 degrees / cm. . On the other hand, the Co and Fe co-substituted titania nanosheet multilayer film (Ti _0.75 Co _0.15 Fe _0.1 O ₂ ) ₁₀ has a wide range of ultraviolet light to near infrared light as shown in FIG. In the wavelength region (wavelength 300-800 nm), a huge magneto-optical effect of about 130,000 degrees / cm enhanced by 10 times or more was shown.

FIG. 5 shows Co and Fe co-substituted titania nanosheets of different compositions (Ti _0.65 Co _0.05 Fe _0.3 O ₂ , Ti _0.7 Co _0.1 Fe _0.2 O ₂ , Ti _0.75 Co It is a magneto-optical spectrum in a multilayer film of _0.15 Fe _0.1 O ₂ ). The magneto-optical effect similar to that of Ti _0.75 Co _0.15 Fe _0.1 O ₂ shown in FIG. 4 (b) is different from the Co and Fe co-substituted titanium oxide nanosheets (Ti _0.65 Co _{0.05) having} different compositions. Fe _0.3 O ₂ , Ti _0.7 Co _0.1 Fe _0.2 O ₂ ) are confirmed in multilayer films, and Co and Fe co-substituted titania nanosheets have high magneto-optical properties, and from ultraviolet light It can be said that it is effective for the development of a magneto-optical element that responds to various wavelengths in a wide wavelength region of near infrared light.

FIGS. 6-8 are the results of evaluating the electronic band structure and optical absorption characteristics of Co and Fe co-substituted titania nanosheets by first-principles calculation for evaluation of the electronic structure related to the magneto-optical effect. The first principle calculation was performed by a local density approximation method (LDA) using a calculation program CASTEP. As the initial structure of the nanosheet, a crystal structure model (FIG. 6) based on the lipidocrosite type TiO ₂ was assumed, and after the structure optimization, the electronic band structure and the optical absorption characteristics were evaluated. For simplicity, the composition was Ti _0.5 Co _0.25 Fe _0.25 O ₂ with a Co / Fe ratio = 1.

  When the stability of the ferromagnetic state was examined for the Co and Fe co-substituted titania nanosheets, it was confirmed that the ferromagnetic state was stable at room temperature as in the experimental results. Further, as a result of the electron band structure shown in FIG. 7, in the Co and Fe co-substituted titanium oxide nanosheet, impurity bands of Co3d and Fe3d appear in the forbidden band, and the number of spin electrons in the upward direction and the number of spins in the downward direction due to the exchange splitting. A large difference in the number of electrons occurred, confirming the ferromagnetic state.

Further, the optical absorption spectrum shown in FIG. 8 reflects the electronic band structure shown in FIG. 7, and in the broad wavelength region from ultraviolet to near infrared light in the forbidden band, the impurity levels of Co and Fe and Co − Optical absorption peaks related to Fe dd transition, ie, Co ²⁺ dd (1.9-2.1 eV), Fe ³⁺ dd (1.7, 2.4-3.0 eV), Co ²⁺ A dd transition of -Fe ³⁺ (~ 2.5 eV) was observed.
These optical absorption peaks are the magneto-optical peaks observed in the Co and Fe co-substituted titania nanosheet multilayer film (Ti _0.75 Co _0.15 Fe _0.1 O ₂ ) shown in FIG. Corresponding to energy (300-460 nm, around 500-800 nm). Thus, the magneto-optical peak of the Co and Fe co-substituted titania nanosheet is due to the strong magnetic interaction of Co ²⁺ (d ⁷ ) -Fe ³⁺ (d ⁵ ). By changing the action, control of the dd transition of Co—Fe, which cannot be realized with a single-substitution titania nanosheet of Co or Fe, was realized, and it is considered that the increase in the strength was caused as the response wavelength increased. .

From the above, the reason why the Co and Fe co-substituted titania nanosheets showed excellent effects in the present invention is that Co ²⁺ dd charge transfer transition (Co ²⁺ → Co ³⁺ ) or Co ²⁺ -Fe ³⁺ (Co ²⁺ -Fe ³⁺ → Co ³⁺ -Fe ²⁺ ) changes the low spin state (s = 1/2) in the initial state Co ²⁺ (d ⁷ ) to the high spin state (s = 2) in Co ³⁺ (d ⁶ ) with excellent magnetic properties. This is considered to be realized.

  FIG. 9 is a diagram showing the performance index and response wavelength of the magneto-optical rotation angle per unit thickness in the magnetic simultaneous substitution titania nanosheet of the present invention. For comparison, the figure of merit and maximum response wavelength of magneto-optical rotation angle per unit thickness are shown for Co, Fe-substituted titania nanosheet multilayer film, Co, Fe-substituted titania nanosheet superlattice, and typical isolator materials. . The magneto-optical effect of the Co, Fe-substituted titania nanosheet multilayer film and the Co, Fe-substituted titania nanosheet superlattice has a performance of 10,000 degrees / cm or more in the ultraviolet to visible wavelength region (260-500 nm), and has a short wavelength. It is optimal for using only ultraviolet to visible light wavelengths. On the other hand, the magneto-optical effect of the magnetic co-substituted titania nanosheet of the present invention is responsive to a wide wavelength region (wavelength 300 to 800 nm) from ultraviolet to near infrared light, and is Co in the ultraviolet to visible wavelength region (260 to 500 nm). , Fe-substituted titania nanosheet superlattice has a figure of merit comparable to that of the superlattice in the visible to near-infrared wavelength region (500-800 nm), and has the world's best figure of merit that far surpasses existing magneto-optic materials.

In this example, a titania nanosheet (Ti _0.75 Co _0.15 Mn ₀ ) in which different magnetic elements (Co, Mn) are simultaneously substituted at a titanium lattice position of a semiconducting titania nanosheet at a concentration of 5% to 20%. _.1 O ₂ , Ti _0.775 Co _0.175 Mn _0.05 O ₂ ), and as shown in FIG. 1, a cationic polymer (polydiallyldimethylammonium chloride ( A multilayer film was produced by alternating self-assembled lamination technique via PDDA)).

The magnetic optical rotation angle is detected by applying a magnetic field of ± 10 kOe at each wavelength from 200 to 900 nm at room temperature to the 10-layer laminated film of Co and Mn co-substituted titania nanosheets thus obtained. The optical spectrum was evaluated. FIG. 10 shows a ten-layer laminated film of Co and Mn co-substituted titania nanosheets (Ti _0.65 Co _0.05 Fe _0.3 O ₂ , Ti _0.7 Co _0.1 Fe _0.2 O ₂ ) having different compositions. FIG. As is apparent from FIG. 10, the same magneto-optical characteristics as those of the Co and Fe simultaneous substitution products are realized also in the Co and Mn simultaneous substitution titania nanosheet, and a wide wavelength region (wavelength 300) from ultraviolet light to near infrared light. -800 nm) showed a giant magneto-optical effect of about 100,000 to 200,000 degrees / cm.

Furthermore, in the magneto-optical spectrum shown in FIG. 10, in the wide wavelength region from ultraviolet to near infrared light within the forbidden band, peaks related to Co, Mn impurity levels and Co—Mn dd transition, Co ²⁺ dd (1.9-2.1 eV), Mn ²⁺ dd * (12.2, 2.5, 2.8 eV), Mn ³⁺ dd (1.0-2.0, 2 .5 eV), Co ²⁺ -Mn ³⁺ (˜2.0 eV) dd transition was observed. Thus, the magneto-optical peak of the Co, Mn co-substituted titania nanosheet is due to the strong magnetic interaction of Co, Mn. By changing the magnetic interaction in the nanosheet by simultaneous substitution, Co, Fe It is considered that the same response wavelength expansion and intensity increase as in the simultaneous substitution product were caused.

As described above, in the present invention, by using Co and Fe co-substitution and Co and Mn co-substitution titania nanosheets as an example, by combining different magnetic elements in the nanosheets simultaneously, strong electron-spin mutual interaction in the two-dimensional nanostructure is achieved. Through this action, a dd transition between magnetic elements that cannot be realized with a single-substitution titania nanosheet of Co, Fe, or Mn was developed, and it was possible to realize an increase in strength along with an increase in response wavelength. Such magnetic interaction is not limited to the combination of Co, Fe, and Mn, but is also a combination of other 3d magnetic elements selected from V, Cr, Mn, Fe, Co, Ni, and Cu, Co ²⁺ , Co It is expected to be realized even in a mixed valence state of the same element such as ³⁺ . This is because the magnetic characteristics of the 3d transition metal element are related to the spin configuration defined by the number of 3d electrons (d ⁿ : n = number of electrons), and Co ²⁺ (d ⁷ ), Fe ³⁺ (d ⁵ The same effect can be obtained with a combination using Ni ³⁺ (d ⁷ ) and Mn ²⁺ (d ⁵ ) having the same spin configuration as that of Ni), that is, Ni ³⁺ -Fe ³⁺ , Ni ³⁺ -Mn ²⁺ , and Co ²⁺ -Mn ²⁺ . It is expected to play.

As described above, according to the present invention, by utilizing the unique magnetic interaction and electronic transition of the magnetic co-substituted titania nanosheet, a high magneto-optical effect in a wide wavelength region from ultraviolet light to near infrared light. It is possible to freely control the fabrication and properties of the magnetic nanofilm showing Devices using the magneto-optic effect have a wide range of applications such as optical isolators, magneto-optical recording elements, magneto-optical sensors, and optical switches. Therefore, the excellent magneto-optical material provided by the present invention can be applied to these technical fields. This is extremely useful.
Among them, the magneto-optical effect is a unique characteristic that can be used as an optical isolator, and an optical isolator using the magneto-optical effect is incorporated in every system of optical communication. Materials that exhibit large magneto-optical properties depending on the wavelength of optical information communication are particularly noteworthy materials. The magnetic element simultaneous substitution titania nanosheet of the present invention has high magneto-optical properties over a wide wavelength range from ultraviolet to near infrared light. Therefore, it is very effective for such applications. For example, a magneto-optical element that responds to lasers of various wavelengths using a magnetic element simultaneous substitution titania nanosheet and a magnetic element having a magnetic function can be realized.

  In addition, garnet-based materials that are currently in practical use as magneto-optical materials have been difficult to fuse with semiconductor elements and molecular electronics. However, magnetic element simultaneous substitution titania nanosheets do not undergo soft chemical reactions such as self-organization. By using it, fusion with various materials is possible, and fusion can be performed at low cost. For example, a magnetic artificial article composed of a thin film in which a magnetic element simultaneous substitution titania nanosheet and an organic polymer, an inorganic polymer, a metal complex, or an inorganic compound containing a polynuclear hydrate ion are combined. A superlattice is feasible. Therefore, it can be concluded that the magnetic co-substituted titania nanosheet of the present invention is extremely useful in the fields of information communication technology such as optical isolators, nanospin electronics, and molecular electronics.

  Furthermore, the material technology based on titania or magnetic semiconductor provided by the present invention is expected to play an active role in the construction of an environment-friendly 21st century IT network society. An environmental problem in the garnet system, which is the current optical isolator material, is a lead-containing problem. In rare earth iron garnet, which is a typical example of an optical isolator, it is indispensable to use lead oxide as a flux during crystal growth. For this reason, about 5000 ppm of lead oxide is contained in the crystal. In July 2006, the European Union decided to eliminate lead contained in electrical and electronic equipment as an environmentally regulated substance in accordance with the RoHS Directive. Therefore, the development of lead-free materials that completely satisfy the standards has been desired. In that respect, the magneto-optical material provided by the present invention is a material that does not contain lead at all based on titania, and is expected to play an important role as a next-generation low environmental load green technology.

  The present invention is applicable to advanced information communication technology fields such as optical isolators and high-density magneto-optical recording by magnetic semiconductor technology and nanotechnology, and transmits visible light and uses ultraviolet light to near infrared light. The aim is to create a magnetic nano-thin film that exhibits high magneto-optical properties in a wide wavelength region.

  The applications of magneto-optics produced by the magnetic simultaneous substitution titania nanosheets provided by the present invention are diverse, including advanced information communication technology fields such as optical isolators, magneto-optical recording elements, magneto-optical sensors, and optical switches. In particular, in the application of optical isolators, the magneto-optical material provided by the present invention is a titania-based material that does not contain lead at all, and plays an active role in building an environmentally friendly 21st century IT network society. It is expected.

  Furthermore, in the present invention, it is possible to realize a low cost and low environmental load process which does not require a large vacuum apparatus or an expensive film forming apparatus, which is the mainstream of conventional thin film processes. Therefore, the magnetic simultaneous substitution titania nanosheet of the present invention is a key component of a magneto-optic material, such as an optical isolator, a magneto-optical recording element, a magneto-optical sensor, and an optical switch, and a technical field such as a nanoelectronics. It is concluded that it is extremely useful when used in

Claims (7)

A non-lead-based magnetic optical device using magnetic nano thin film, the magnetic element the magnetic nano thin film is obtained a layered titanic oxide were simultaneously replaced with two different magnetic elements in the titanium lattice sites by a single layer peeling Ri Do from simultaneous substitution titania nano-sheet,
The two combinations of magnetic elements each ^Co 2+ ^{(d 7)} and ^Fe 3+ ^{(d 5)} and the non-lead-based magnetic optical element to which is a combination wherein <br/> that elements having the same spin configuration. The magnetic element simultaneous substitution titania nanosheet has a composition formula Ti _1-xy M _x M ′ _y O ₂ (where M is a magnetic metal selected from V, Cr, Mn, Fe, Co, Ni, Cu, M The non-lead according to claim 1, wherein 'is represented by at least one magnetic metal other than M selected from V, Cr, Mn, Fe, Co, Ni, and Cu, 0 <x + y <1) Magnetic optical element.   The lead-free magnetic optical element according to claim 2, wherein M and M 'are the same element, and the valences of M and M' are different from each other. The lead-free magnetic material according to claim 1, wherein the magnetic element simultaneous substitution titania nanosheet is represented by a composition formula Ti _1-xy Co _x Fe _y O ₂ (where 0 <x + y <1). Optical element.   The magnetic nano thin film is a thin film in which a magnetic element simultaneous substitution titania nano sheet and an organic polymer, an inorganic polymer, a metal complex, or an inorganic compound containing a polynuclear hydrate ion are combined. The lead-free magneto-optical element according to claim 1, wherein A method of manufacturing a non-lead-based magnetic optical element according to any one of claims 1 to 5, the resulting layered titanic oxide were simultaneously substituting two different magnetic elements in the titanium lattice sites by a single layer peeling A method for producing a lead-free magnetic optical element, wherein a magnetic nano-thin film is formed by laminating magnetic element simultaneous substitution titania nanosheets on a substrate via an organic polycation as a cationic substance.   7. The method for producing a lead-free magnetic optical element according to claim 6, wherein the magnetic nano thin film is formed by spin-coating or dip-coating the magnetic element simultaneous substitution titania nanosheet on the substrate.