JP2006114489A - Dielectric meta-material and magnetic substance meta-material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material with electric characteristics such as magnetic characteristics and dielectric characteristics marvelously heightened. <P>SOLUTION: The complex material (the meta-material) is formed by periodically arranging magnetic substances or dielectrics. Soft material is used for their bonding. The shapes of the magnetic substance and the dielectric substance is cuboid or pseudo-cuboid formed by slightly deforming the cuboid, and the meta-material is aggregation of the cuboid-shaped substance or the pseudo-cuboid-shaped substance, or combination thereof. The meta-material is formed by periodically arranged them in three dimension, and bonded to each other by the soft material. By arranging these materials periodically (in one to three dimensions), the materials with higher dielectric and magnetic characteristics than the original material can be provided. Barium titanate(BaTiO<SB>3</SB>), forsterite, willemite or the like is utilized for the dielectric which can obtain a dielectric constant several times larger than that of original material. As for the magnetic substances, strong magnetic characteristics, stronger than that of Fe<SB>14</SB>Nd<SB>2</SB>B, can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metamaterial using a dielectric material or a magnetic material.

Conventionally, barium titanate (BaTiO ₃ ) is known as an existing dielectric material having the maximum dielectric constant. In addition, neodiiron boron (Fe ₁₄ Nd ₂ B) compound is known as a ferromagnetic material having the largest existing magnetism.

Barium titanate (BaTiO ₃ ), which is a dielectric material, is practically used as a capacitor material due to its ferroelectricity. In addition, there are strontium titanate, forsterite, and wilmite as dielectric materials, which are practically used in the field of wireless communication such as resonators and antennas.

On the other hand, neodiiron boron (Fe ₁₄ Nd ₂ B) compound, which is a ferromagnetic material, has large magnetic properties because it has crystal electric field anisotropy (CEF) and shape anisotropy. Iron, which is also a ferromagnetic material, has a large magnetic property because of its strong particle shape anisotropy. These are practically used as materials for motors and magnetic recording.

An example of a memory element material using a ferromagnetic material and a ferroelectric material is disclosed in Patent Document 1.
JP 2002-118237 A

  If the dielectric constant and magnetic permeability (magnetic properties) of the above dielectric materials and magnetic materials can be further increased, it is possible to realize capacitors, resonators, antennas, motors, magnetic recording materials, and the like with higher performance and smaller size. It is.

  As a result of intensive studies to achieve this improvement, the present inventors periodically arranged unit structures formed by existing dielectric materials and magnetic materials, thereby permitting dielectric constant and permeability to be obtained. It has been found that the dielectric material and magnetic material, which are raw materials, can be dramatically increased compared to the dielectric constant and magnetic permeability originally provided.

  That is, a first invention for solving the above-described problem is a dielectric in which a plurality of unit structures formed of a dielectric material are periodically arranged and the unit structures are coupled to each other by a soft material. Metamaterial.

  The second invention is a magnetic metamaterial in which a plurality of unit structures formed of a magnetic material are periodically arranged and the unit structures are bonded to each other with a soft material.

  Here, “periodically arranged” may be any arrangement as long as it is arranged with a specific periodicity. For example, a one-dimensional period in which a plurality of unit structures are arranged in a straight line. The structure may be a two-dimensional periodic structure such as a square lattice structure, a triangular lattice structure, or the like, a face-centered cubic lattice structure, a body-centered cubic lattice structure, or a simple structure. It may be a three-dimensional periodic structure that is regularly arranged three-dimensionally, such as a cubic lattice structure.

  According to the present invention, a plurality of unit structures formed of a dielectric material are periodically arranged and combined with a soft material to form a dielectric metamaterial. Compared with the inherent characteristics, it can be dramatically improved.

In addition, by periodically arranging a plurality of unit structures formed of magnetic material and combining them with a soft material to form a magnetic metamaterial, the magnetic properties are the same as those inherent in the magnetic material that is the material. Compared to this, it can be improved dramatically. By arranging the magnetic material periodically, the magnetic flux density B increases particularly in the low frequency region. In particular, when neodiiron boron (Fe ₁₄ Nd ₂ B) is used as the magnetic material, the magnetic metamaterial is surprisingly larger than the magnetic permeability inherent in the neodiiron boron that is the material.

  Such a dielectric metamaterial / magnetic metamaterial can be used as a material such as a capacitor, a resonator, an antenna, a motor, and a magnetic recording material that can be miniaturized with high performance.

  The dielectric metamaterial or magnetic metamaterial of the present invention (hereinafter may be abbreviated as “metamaterial”) is a unitary arrangement of dielectric materials or magnetic materials, and is bonded with a soft material. Is.

Although there is no restriction | limiting in particular as a dielectric material which comprises a unit structure, A ferroelectric material or a paraelectric material can be used preferably. More specifically, barium titanate (BaTiO ₃ ), strontium titanate (SrTiO ₃ ), forsterite (Mg ₂ SiO ₄ ), Wilmite (Zn ₂ SiO ₄ ) and the like can be preferably used. Among these, as forsterite and wilmite, rutile-added forsterite and rutile-added wilmite whose temperature coefficient of resonance frequency is adjusted to around 0 ppm / ° C. by adding rutile-type titanium oxide can also be used.

The magnetic material constituting the unit structure is not particularly limited, but neodiiron boron (Fe ₁₄ Nd ₂ B), iron (Fe), nickel (Ni), and samarium cobalt (SmCo ₅ ) are particularly preferably used. can do.

“Soft material” refers to a material that has no hysteresis when an electric or magnetic field is applied. Examples of soft materials suitable for the dielectric metamaterial of the present invention include, for example, rutile titanium oxide (TiO ₂ ), SrTiO ₃ , CeTiO ₃ , NiO ₂ , Cu, Bi, graphite, polytetrafluoroethylene (PTFE), and thermoplasticity. Examples thereof include a resin and a thermosetting resin. Soft materials suitable for magnetic metamaterials include rutile titanium oxide (TiO ₂ ), SrTiO ₃ , CeTiO ₃ , NiO ₂ , Fe, Ni, Cu, Bi, graphite, polytetrafluoroethylene (PTFE), heat A plastic resin, a thermosetting resin, Si, etc. can be mentioned.

  For example, some dielectric materials can be used as a material constituting a unit structure, and can also be used as a soft material for connecting unit structures to each other. However, a unit structure and a soft material constituting one metamaterial can be used. For materials, it is necessary to use different materials.

1 to 5, metamaterials M _{1 to} M in which unit structures P _{1 to} P ₅ formed of a dielectric material or a magnetic material are periodically arranged and combined with soft materials S _{1 to} S _5. The example of ₅ is shown. The periodic structure of the metamaterials M _{1 to} M ₅ may be a one-dimensional periodic structure in which a plurality of unit structures P ₁ or P ₂ are arranged one-dimensionally, for example, as shown in FIGS. as shown in FIG. 3, may be a two-dimensional periodic structure unit structure P ₃ are arranged two-dimensionally, as shown in FIGS. 4 and 5, the unit structure P _4, P ₅ is 3-dimensionally It may be a three-dimensional periodic structure to be arranged. In particular, a three-dimensional periodic structure is effective for improving dielectric characteristics or magnetic characteristics.

  The shape of the unit structure P is not particularly limited. For example, the unit structure P may be a rectangular parallelepiped as shown in FIG. 1, a cube as shown in FIG. 2, or a shape such as a cylinder (see FIG. 7). You can also take In particular, the shape is preferably a cube, a pseudo cube obtained by modifying a cube, or a combination of a cube and a pseudo cube. Here, “deformed” includes, for example, changing the side length and angle of a cube (regular hexahedron), cutting a vertex, and the like. Examples thereof include a rectangular parallelepiped that is partially or entirely rectangular, and a truncated hexahedron (truncated-cube) that is a 14-sided shape in which a vertex of a cube is cut.

  An example of a method for creating a metamaterial of the present invention will be described with reference to FIGS. 6A to 6C.

First, a plate 11 made of a dielectric material (or a magnetic material) and a resin sheet 12 made of a resin that is a soft material are prepared. Then, a plurality of the plates 11 are laminated with the resin sheet 12 interposed therebetween to produce a laminate 13 (FIG. 6A). Next, the laminated body 13 is irradiated in the direction in which the plate 11 is laminated by irradiating the laminated body 13 with laser light from a direction (Z-axis direction) orthogonal to the plate surface of the plate 11 using, for example, a carbon dioxide laser device. A plurality of points are cut along the line (FIG. 6B). In FIG. 6B, the stacked body 13 is divided into a plurality of rows (specifically, 5 rows in the X-axis direction and 4 rows in the Y-axis direction) in two directions intersecting the stacking direction (Z-axis direction) of the plates 11. Although it is divided, the mode of division is not particularly limited to this example, and it is sufficient that a plurality of plate pieces (unit structure P ₆ ) divided and formed by division are periodically arranged. Next, the gap 14 formed at the cutting position of the laminate 13 is filled with the same kind of resin as the material of the resin sheet 12, and the outer peripheral surface of the laminate 13 is coated with the same resin. In this way, a plurality of unit structures P ₆ (plate pieces) formed of a dielectric material (or magnetic material) are arranged three-dimensionally, and are mutually soft material S ₆ (resin sheet 12 and gap 14). metamaterial M ₆ coupled is completed for the use in filling and the surface coating resin) (FIG. 6C).

  Next, another example of the method for creating a metamaterial of the present invention will be described with reference to FIGS. 7A to 7C.

  First, a paste 21 of dielectric material or magnetic material is prepared. The paste 21 comprises a raw material powder for sintering a dielectric material or magnetic material, a resin (for example, thermoplastic cellulose ether “Etocel (registered trademark)” manufactured by Dow Chemical Company), and an organic solvent (for example, terpineol). It can be prepared by the usual method of kneading with this roll mill.

  At the same time, a soft material green sheet 22 is prepared. First, the ceramic raw material powder constituting the soft material, an organic binder (for example, butyral resin, acrylic resin), a plasticizer, and an organic solvent (for example, a mixed solution of methyl ethyl ketone, ethanol, and toluene) are mixed in a pot. Thus, a raw material slurry of soft material is obtained. This raw material slurry is cast (coated) on a PET (polyethylene terephthalate) carrier member in a thin and uniform thickness using an ordinary doctor blade casting apparatus, and then dried by heating at about 70 ° C. with a heater. The green sheet 22 is obtained by volatilizing most of the volatile components therein. The green sheet 22 is cut using a known means such as a punching die to obtain a predetermined size.

  Next, a plurality of through holes 23 penetrating in the thickness direction are formed in the green sheet 22 using a mechanical punch device or a carbon dioxide gas laser device (FIG. 7A). In FIG. 7A, the through holes 23 are arranged in two vertical rows and four horizontal rows, but the arrangement of the through holes is not particularly limited to the arrangement of FIG. Next, the through holes 23 are filled with a paste 21 containing a dielectric material or a magnetic material, for example, by screen printing.

Next, a plurality of green sheets 22A thus formed with the through holes 23 and filled with the paste 21 are stacked with the green sheets 22B having no through holes 23 interposed therebetween. Then, by applying a pressing force (for example, about 5000 kgf / cm ² ) in the sheet stacking direction under a predetermined temperature condition (for example, 80 ° C.) using a laminating apparatus, the green sheets 22A and 22B are pressed and integrated. Then, the laminate 24 is formed (FIG. 7B).

Finally, the laminate 24 is degreased (at 250 ° C. for about 10 hours), and further fired at a predetermined temperature for a predetermined time. Thereby, the raw material powder of the dielectric material or the magnetic material contained in the paste 21 is sintered, and the unit structure P _{7 of} the dielectric material or the magnetic material is obtained. Further, green sheets 22A, also the raw material powder of ceramics contained in 22B sintered couples a unit structure P ₇ each other. In this way, the unit structure P ₇ is periodically arranged, metamaterial M ₇ joined by soft materials S ₇ are obtained from each other (Fig. 7C). In addition, you may cut the laminated body 24 into a suitable magnitude | size as needed before baking.

<Example 1-1>
In order to verify the effect of increasing the dielectric properties of the dielectric metamaterial, the S parameter of the dielectric metamaterial in which unit structures of barium titanate (BaTiO ₃ ) are periodically arranged was obtained by computer simulation.

The unit structure P ₁ barium titanate as illustrated in FIG. 1 is three series in the Z axis direction, coating the surface with coupling between adjacent unit structures P ₁ in soft materials S ₁ with the same soft materials S ₁ and the ones with the unit cell G _1. The unit cell G ₁ has four reflective surfaces. By multiple parallel the unit cell G ₁ in the XY direction, were designed dielectric metamaterials three-dimensional periodic structure as illustrated in FIG. However, the unit cell _{G 1} is 20 rows in the X-axis direction and 20 columns arranged in the Y-axis direction. The dimensions of the unit structure P ₁ are width W ₁ × depth L ₁ × height H ₁ = 0.18 mm × 0.18 mm × 0.3 mm, and the dimensions of the unit cell G ₁ are width W ₂ × depth L _2. × Height H ₂ = 0.2 mm × 0.2 mm × 1 mm

  With respect to the dielectric metamaterial thus designed, S parameters were analyzed by computer simulation using FDTD (Finte Difference Time Domain) and FEM (Finte Element Method).

  The analysis result of the S parameter by computer simulation is shown in FIG. By forming the metamaterial, a resonance peak was observed near 28 GHz.

<Example 1-2>
As illustrated in FIG. 2, five unit structures P _{2 of} barium titanate are connected in series in the Z-axis direction, and adjacent unit structures P ₂ are connected with the soft material S ₂ and the surface is coated with the same soft material S ₁ . and the ones with the unit cell G _2. The unit cell G ₂ is, having six reflecting surfaces. By multiple parallel the unit cell G ₂ in the XY directions, were designed dielectric metamaterials three-dimensional periodic structure as illustrated in FIG. However, the unit cell _{G 2} is, 20 rows in the X-axis direction and 20 columns arranged in the Y-axis direction. The unit structure P ₂ has a width W ₃ × depth L ₃ × height H ₃ = 0.18 mm × 0.18 mm × 0.18 mm, and the unit lattice G ₂ has a width W ₄ × depth L _4. X Height H ₄ = 0.2 mm x 0.2 mm x 1 mm

  For the dielectric metamaterial thus designed, S parameters were analyzed by computer simulation in the same manner as in Example 1-1.

  The analysis result of the S parameter by computer simulation is shown in FIG. As compared with Example 1-1, a shift of the S-parameter resonance peak toward the low frequency side was observed by increasing the number of periods in the Z-axis direction from 3 to 5. This leads to an increase in dielectric constant.

<Example 2-1>
A magnetic metamaterial having a three-dimensional periodic structure was designed in the same manner as in Example 1-1 except that a magnetic material having a magnetic permeability μ = 2000 was used instead of barium titanate in Example 1-1, and a computer was designed. A simulation was performed.

  The analysis result of the S parameter by computer simulation is shown in FIG. By forming the metamaterial, a resonance peak was observed around 20 GHz.

<Example 2-2>
A magnetic metamaterial having a three-dimensional periodic structure was designed in the same manner as in Example 1-2, except that a magnetic material having a magnetic permeability μ = 2000 was used instead of barium titanate in Example 1-2, and the computer A simulation was performed.

  The analysis result of the S parameter by computer simulation is shown in FIG. As compared with Example 2-1, by increasing the number of periods in the Z-axis direction from 3 to 5, a shift of the resonance peak of the S parameter to the high frequency side was observed. This leads to an increase in permeability.

<Example 3>
In order to verify the effect of increasing the magnetic properties of the magnetic metamaterial, S parameters of the magnetic metamaterial in which iron unit structures are periodically arranged were obtained by computer simulation.

As shown in FIG. 12, 20 penetrates in the width direction through a block of resin (soft material S ₈ ) formed in a width W ₅ × depth L ₅ × height H ₅ = 2.25 mm × 2.25 mm × 45 mm. The through holes 30 were formed at a uniform pitch in the height direction. By inserting the unit structure P ₈ consisting of iron wire in the through-hole 30, to prepare a metamaterial M _8.
For the magnetic metamaterial thus designed, S parameters were analyzed by computer simulation using Broadband Microstrip Based Method.

FIG. 13 shows the result of computer simulation analysis of the S parameter of the magnetic metamaterial (shown as S21wires and S22wires in the figure). Incidentally, in FIG. 13, (shown in Fig, S21holes, as S22holes) As a control, the analysis results are also shown for the block of soft materials S ₈ without insert the unit structure P ₈ in the through hole 30. In the S parameter of the metamaterial, an increase in resonance peak and a shift toward the low frequency side were observed as compared with the control.

A perspective view showing an example of a metamaterial having a one-dimensional periodic structure Perspective view showing another example of a metamaterial having a one-dimensional periodic structure A perspective view showing an example of a metamaterial having a two-dimensional periodic structure A perspective view showing an example of a metamaterial having a three-dimensional periodic structure The perspective view which shows the other example of the metamaterial of a three-dimensional periodic structure The perspective view which shows the laminated body which laminated | stacked the plate produced with dielectric material (or magnetic material) on both sides of the resin sheet The perspective view which shows a mode that cut | interrupted the laminated body Perspective view showing the completed metamaterial A perspective view showing a through-hole formed in a soft material green sheet The perspective view which shows the laminated body which laminated | stacked the green sheet Perspective view showing the completed metamaterial Chart showing the results of computer simulation of S-parameters using a free space method for a dielectric metamaterial with a three-dimensional periodic structure using barium titanate as the dielectric material and having a period number of 3 in the Z-axis direction Chart showing results of computer simulation of S parameters for a dielectric metamaterial having a three-dimensional periodic structure in which barium titanate is used as a dielectric material and the number of periods in the Z-axis direction is 5. The chart which shows the result of having performed the computer simulation of S parameter about the magnetic metamaterial of the three-dimensional periodic structure which uses the magnetic material of magnetic permeability (micro | micron | mu) = 2000, and the number of periods of the Z-axis direction is 3. The chart which shows the result of having performed the computer simulation of S parameter about the magnetic metamaterial of the three-dimensional periodic structure which uses the magnetic material of magnetic permeability (micro | micron | mu) = 2000, and the number of periods of the Z-axis direction is 5. The perspective view which shows the structure of the magnetic substance metamaterial used for Example 3 Chart showing results of computer simulation of S parameters for magnetic metamaterial using iron as magnetic material

Explanation of symbols

M ... Metamaterial (dielectric metamaterial, magnetic metamaterial)
P ... Unit structure S ... Soft material

Claims (9)

  A dielectric metamaterial in which a plurality of unit structures formed of a dielectric material are periodically arranged and the unit structures are bonded to each other by a soft material.   2. The dielectric metamaterial according to claim 1, wherein the unit structure is a cube, a pseudo cube obtained by modifying a cube, or a combination of the cube and the pseudo cube.   The dielectric metamaterial according to claim 1, wherein the dielectric material is a ferroelectric material or a paraelectric material. The dielectric material is one selected from the group consisting of barium titanate (BaTiO ₃ ), strontium titanate (SrTiO ₃ ), forsterite (Mg ₂ SiO ₄ ), and wilmite (Zn ₂ SiO ₄ ). The dielectric metamaterial according to any one of claims 1 to 3, wherein the dielectric metamaterial is characterized. The soft material is selected from the group consisting of rutile titanium oxide (TiO ₂ ), SrTiO ₃ , CeTiO ₃ , NiO ₂ , Cu, Bi, graphite, polytetrafluoroethylene (PTFE), a thermoplastic resin, and a thermosetting resin. The dielectric metamaterial according to claim 1, wherein the dielectric metamaterial is at least one selected from the group consisting of:   A magnetic metamaterial in which a plurality of unit structures formed of a magnetic material are periodically arranged and the unit structures are bonded to each other by a soft material.   7. The magnetic metamaterial according to claim 6, wherein the unit structure is a cube, a pseudo cube obtained by deforming a cube, or a combination of both. The magnetic material is one selected from the group consisting of neodiiron boron (Fe ₁₄ Nd ₂ B), iron (Fe), nickel (Ni), and samarium cobalt (SmCo ₅ ). Item 8. A magnetic metamaterial according to Item 6 or Claim 7. The soft material is rutile titanium oxide (TiO ₂ ), SrTiO ₃ , CeTiO ₃ , NiO ₂ , Fe, Ni, Cu, Bi, graphite, polytetrafluoroethylene (PTFE), thermoplastic resin, thermosetting resin, and The magnetic metamaterial according to any one of claims 6 to 8, wherein the magnetic metamaterial is at least one selected from the group consisting of Si.

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