KR20160107568A - Composite magnetic sheet and magneto-dielectric antenna using thereof - Google Patents

Abstract

The present invention relates to a composite magnetic sheet, and a magneto-dielectric antenna using the same. According to the present invention, the composite magnetic sheet comprises: an antiferromagnetic layer and a ferromagnetic layer which come in contact with each other; and patterns formed on an interface between the antiferromagnetic layer and the ferromagnetic layer, thereby increasing a coercive force by an exchange bias in the interface between the antiferromagnetic layer and the ferromagnetic layer. As such, the present invention simultaneously satisfies properties of high permeability and loss of low permeability in a GHz band by increasing a resonance frequency through an increase in coercive force.

Description

TECHNICAL FIELD [0001] The present invention relates to a composite magnetic sheet and a magnetic antenna using the same. BACKGROUND OF THE INVENTION < RTI ID = 0.0 >

The present invention relates to a composite magnetic sheet and a magnetic body antenna using the same.

In recent years, along with downsizing, high-speed, and high-frequency electronic devices, electronic components used in these electronic devices have been demanded to have high efficiency characteristics in a frequency band of several hundred MHz to several GHz along with miniaturization.

To this end, a technology has been proposed in which spinel ferrites such as NiZn-based ferrite are used to miniaturize an antenna while maintaining gain. But, Spinel ferrites have a high magnetic permeability in a low frequency band, but the permeability is rapidly lowered due to the Snoek's limit in a high frequency band of several hundred MHz or more, and thus it is difficult to use them as magnetic materials for high frequency electronic parts.

Hexa type magnetic materials having a high permeability even in a high frequency band beyond the threshold of spinel ferrite have been studied. However, the magnetic permeability of the hexa-type magnetic material also decreases sharply in the high frequency band exceeding 1 GHz It is known.

Therefore, research on magnetic materials capable of satisfying high permeability and low investment loss simultaneously in a high frequency band of 1 GHz or more is required.

Japanese Patent Application Laid-Open No. 2003-196818

It is an object of the present invention to provide a semiconductor device having a high permeability and a low investment loss characteristic suitable for a high- And to provide a composite magnetic sheet.

Another object of the present invention is to provide a magnetic antenna which is equipped with the composite magnetic sheet and is suitable for use in a high frequency band of 1 GHz or more.

The object of the composite magnetic sheet according to the present invention is that,

And to provide a magnetic material capable of overcoming a decrease in permeability due to material limitations of a magnetic material applied to a high frequency magnetic body antenna of 1 GHz or more.

To this end, the present invention provides a novel structure including a pattern at the junction interface between the antiferromagnetic layer and the ferromagnetic layer so as to widen the area (bonding area or contact area) between the antiferromagnetic layer and the ferromagnetic layer per unit volume in the sheet Of the magnetic composite sheet.

At this time, the pattern may be a concave-convex shape or a core-shell structure in which alternately stacked antiferromagnetic layers and ferrimagnetic layers are arranged in a direction perpendicular to the upper surface of the sheet Coaxial < / RTI >

The composite magnetic sheet according to the present invention includes a pattern having a constant shape that widens the area (contact area) between the antiferromagnetic layer and the ferromagnetic layer per unit volume, so that the resonance frequency is increased by increasing the coercive force due to the exchange bias at these interfaces So that high permeability and low investment loss characteristics can be satisfied at the same time in the region of 1 GHz or more.

Further, according to the present invention, it is possible to manufacture a magnetic body antenna having a composite magnetic sheet of the above-described characteristics and suitable for use in a high frequency band of 1 GHz or more.

1 is a perspective view of a composite magnetic sheet according to a first embodiment of the present invention.
Figure 2 is a cross-sectional view of Figure 1;
3 is a view showing a pinning phenomenon of a spin in a pattern of the composite magnetic sheet according to the first embodiment of the present invention.
4 is a graph showing the magnetization curves of the hexaferrite powder and the magnetization curves of the antiferromagnetic-ferrimagnetic composite magnetic material according to the first embodiment of the present invention.
5 is a cross-sectional view of a composite magnetic sheet according to a second embodiment of the present invention.

The advantages and features of the present invention and the techniques for achieving them will be apparent from the following detailed description taken in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The present embodiments are provided so that the disclosure of the present invention is not only limited thereto, but also may enable others skilled in the art to fully understand the scope of the invention.

The terms used herein are intended to illustrate the embodiments and are not intended to limit the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is to be understood that the terms 'comprise', and / or 'comprising' as used herein may be used to refer to the presence or absence of one or more other components, steps, operations, and / Or additions.

In addition, the components of the drawings are not necessarily drawn to scale; for example, the dimensions of some of the components of the drawings may be exaggerated relative to other components to facilitate understanding of the present invention. In the meantime, the same reference numerals denote the same elements throughout the drawings, and for the sake of simplicity and clarity of illustration, the drawings illustrate a general constructional scheme and are intended to unnecessarily obscure the discussion of the described embodiments of the present invention Detailed descriptions of known features and techniques may be omitted so as to avoid obscuring the invention.

The present invention provides a composite magnetic sheet having a pattern at a bonding interface between an antiferromagnetic layer and a ferrimagnetic layer so as to widen the area (contact area) between the antiferromagnetism layer and the ferrimagnetism layer .

Hereinafter, a composite magnetic sheet according to the present invention and a magnetic material antenna using the same will be described in detail with reference to FIGS. 1 to 5.

Fig. 1 is a perspective view of a composite magnetic sheet according to a first embodiment of the present invention, and Fig. 2 is a cross-sectional view of Fig. 1. Fig.

As shown in FIG. 1, the composite magnetic sheet 100 of the first embodiment of the present invention is configured such that a pattern 110 of a predetermined shape is included in a polymer matrix 120.

The pattern 110 is a composite magnetic body composed of an antiferromagnetism material and a ferrimagnetism or a quasi-ferromagnetic material and has a columnar core 110a and a core And a shell 110b surrounding the outer circumferential surface of the core 110a.

The core 110a has a certain shape, for example, a cylindrical shape, or a prismatic shape such as a square, a triangle, or a pentagon, and is arranged in a direction perpendicular to the upper surface of the composite magnetic sheet 100. [ In Fig. 1, a cylindrical core 110a is shown.

At this time, the core 110a may be an antiferromagnetic layer or a ferrimagnetic layer.

Here, the antiferromagnetic layer has the same magnetic moment as the neighboring atom but is arranged in the opposite direction so that the total magnetic moment becomes 0. However, when a small lattice formed by the magnetic principle oriented in the same direction is taken, Lt; RTI ID = 0.0 > antiferromagnetic < / RTI > material.

The antiferromagnetic layer is preferably formed to include an antiferromagnetic material having a Neel temperature of about 300K or more, since the temperature at which the antenna is used is higher than room temperature and therefore, it must have magnetism at room temperature.

At this time, if the kneading temperature of the antiferromagnetic material contained in the antiferromagnetic layer is less than 300 K, the exchange-bias effect can not be exhibited at room temperature.

In one example, the antiferromagnetic layer may comprise an antiferromagnetic material such as NiO or Cr.

The ferrimagnetic layer is a layer formed by including a ferrimagnetic material in which the magnetic moments of atoms are arranged in opposite directions to the magnetic moments of neighboring atoms, but the magnetic moments are different in size and magnetized by the difference.

Since such a ferrimagnetic layer should be used at a high frequency of several to several tens of GHz, a hexagonal ferrite material can be preferably used, and more preferably a magnetocrystalline anisotropy ratio (H _? / H _?, H _? : Axial magnetic anisotropy, H _?: Plane magnetic anisotropy) can be used as the Y-type or Z-type hexaferrite material.

Generally, the hexaferrite material has an easy magnetization direction in the plane perpendicular to the c-axis of the crystal, so that the magnetic anisotropy characteristic is larger. Therefore, the frequency range of the spinel ferrite exceeds the frequency limit of the spinel ferrite And is known to maintain a predetermined permeability. Therefore, the hexaferrite material can be used in the high frequency band of several to several tens of GHz band.

The hexaferrite material may have any one of crystal structure selected from M type, U type, W type, X type, Y type and Z type, and the resonance frequency f _r and initial permeability (μ _i ) Are shown in Table 1 below.

ferrite
type The Ms
(emu / g) Hc
(Oe) Tc
(K) f _r
(GHz) μ _i
BaM BaFe ₁₂ O ₁₉ 72 3200 450 43.5 <2 SrM SrFe ₁₂ O ₁₉ 74 ~ 92 3590 460 50 <2 Co ₂ Y Ba ₂ Co ₂ Fe ₁₂ O ₂₂ 34 55.2 340 5.7 3 Co ₂ Z Ba ₃ Co ₂ Fe ₂₄ O ₄₁ 50 108 410 1.3 to 3.4 19 Co ₂ W BaCo ₂ Fe ₁₆ O ₂₇ 54.78 5.88 490 1-3 ~ 3.5 Co ₂ X Ba ₂ Co ₂ Fe ₂₈ O ₄₆ 69 - 501 1.2 ~ 2.5 Co ₂ U Ba ₄ Co ₂ Fe ₃₆ O ₆₀ 51 175 ~ 1598 434 30 to 40 ~ 1.3

(Where Ms is the saturation magnetization, Hc is the coercive force, and Tc is the crystallization temperature)

As shown in Table 1, the Z-type hexaferrite material has a relatively high initial permeability (mu _i ) and exhibits excellent high-frequency characteristics, which is advantageous for miniaturization of the antenna.

Since the Y type hexaferrite material exhibits intermediate characteristics between the M type and the Z type, it has a high magnetic permeability in the initial frequency range of the GHz band and a low loss characteristic due to a relatively high self resonance frequency (SRF) characteristic. And is one of a group of materials having a high possibility as a magnetic material for high frequency of 1 GHz or more.

The hexaferrite material may be represented by the following formula (1), and the Y-type hexaferrite material may be represented by the following formula (2).

[Chemical Formula 1]

Ba _1-x Sr _x Co _1-y [Me] _y Fe _m O _n

1, 0 <y <1, 12 <m <36 and 19 <n <60), where [Me]

(2)

Ba _1-x Sr _x Co _1-y [Me] _y Fe ₁₂ O ₂₂

(Where Me is one selected from Zn, Mn and Cu, 0 < x < 1, 0 <

The shell 110b coated on the outer circumferential surface of the core 110a may be composed of at least one layer of a single layer or multiple layers. The number of layers of the shell 110b can be variously changed according to the design. In FIG. 1, a shell 110b composed of three layers of the first through third subshells 110b1, 110b2, and 110b3 is shown.

When the shell 110b is composed of a single layer, the shell 110b is formed of an antiferromagnetic layer or a ferrimagnetic layer having a magnetic property different from that of the core 110a. For example, when the core 110a is formed of an antiferromagnetic layer, the shell 110b is formed of a ferrimagnetic layer.

When the shell 110b is formed in a multilayer structure, the first subshell 110b1, which is in contact with the core 110a, is formed of an antiferromagnetic layer or ferrimagnetic layer having a different magnetic property from the core 110a, The three sub-shells 110b2 and 110b3 are selected from an antiferromagnetic layer or a ferrimagnetic layer depending on the material of the second subshell 110b2 so that the antiferromagnetic layer and the ferrimagnetic layer are alternately stacked in the shell 110b.

For example, if the core 110a is formed of an antiferromagnetic layer, the first sub-shell 110b1 is formed of a ferrimagnetic layer, the second sub-shell 110b2 is formed of an antiferromagnetic layer, and the third sub- Ferrimagnetic layer.

With this structure, the pattern 110 has a core-shell structure in which the antiferromagnetic layer and the ferrimagnetic layer are alternately stacked, and the coplanar (coplanar) structure in which the coplanar coaxial.

In FIG. 1, six patterns 110 are shown for convenience of explanation. However, the number of patterns 110 is not limited to at least one, and may be variously changed depending on the design.

Generally, in order for a ferrite material to have a high permeability in a GHz region, the field direction anisotropy field must be small. In this case, the resonance frequency is low. This is because the resonance frequency is proportional to the plane anisotropy field value as shown in the following equation (1).

Here, f _r is a resonance frequency, γ is a gyromagnetic factor, H _θ is an axial magnetic anisotropy field, and H _φ is a plane direction anisotropic magnetic field)

A method of changing the lattice structure of the magnetic material to change the planar anisotropy field has recently been attempted. However, this method requires a lot of time for material development because the material is designed and proceeded, and the time from material production to sheet development takes a lot of time as the specification of the existing production material is changed.

Alternatively, simple lamination of soft magnetic hexaferrite material and hard magnetic antiferromagnetic material has been introduced, but this also has limitations in increasing coercivity (Hc).

In order to solve the above-described problems, the present invention introduces a pattern 110 into the composite magnetic sheet 100, and the effect of forming the pattern 110 will be described in detail below.

As described above, the first embodiment of the present invention is a composite magnetic sheet 100 (100) including a coaxial pattern 110 of a core 110a-shell 110b structure in which an antiferromagnetic layer and a ferromagnetic layer are alternately stacked ).

FIG. 3 is a view showing pinning phenomena of a spin in a pattern of a composite magnetic sheet according to the first embodiment of the present invention, showing an antiferromagnetic layer core 110a and a ferrimagnetic layer shell 110b.

As shown in FIG. 3, at the interface between the antiferromagnetic layer and the ferromagnetic layer in the pattern 110 of the sheet having such a configuration, exchange-bias (or exchange anisotropy) The pinning (P) of the coercive force is generated, thereby increasing the coercive force.

The increase of the coercive force by the exchange bias means the increase of the planar direction anisotropic magnetic field, and the increase of the planar direction anisotropic magnetic field has the effect of increasing the resonant frequency by Equation (1).

As a result, the first embodiment of the present invention is able to simultaneously satisfy the high permeability and the low investment loss characteristic in the GHz range by increasing the resonance frequency by increasing the anisotropic magnetic field in the plane direction of the composite magnetic sheet 100 .

On the other hand, the coercive force tends to increase in proportion to the exchange coupling region in which the exchange bias is generated. That is, the strength of the magnetic coupling between the antiferromagnetic layer and the ferrimagnetic layer depends on the ratio of the volume between the antiferromagnetic layer and the ferrimagnetic layer.

Accordingly, in order to increase the coercive force by bonding the antiferromagnetic material to the ferrimagnetic material, it is necessary to increase the exchange coupling area by widening the area (contact area) between the antiferromagnetic layer and the ferrimagnetic layer.

In the first embodiment of the present invention, the coaxial pattern 110 of the core 110a-shell 110b structure in which the antiferromagnetic layer and the ferrimagnetic layer are alternately stacked has a total area per unit volume between the antiferromagnetic layer and the ferrimagnetic layer It will play a role of spreading.

As a result, the exchange coupling area between the antiferromagnetic layer and the ferromagnetic layer is relatively increased as compared with the case where the antiferromagnetic layer and the ferrimagnetic layer are simply stacked. Therefore, it is more effective in increasing the coercive force and more effective in increasing the resonant frequency by increasing the coercive force to be.

4 is a graph showing the magnetization curves of the hexaferrite powder and the antiferromagnetic-ferrimagnetic composite magnetic material according to the first embodiment of the present invention, wherein A is the magnetization curve of the hexaferrite powder, Is the magnetization curve of the antiferromagnetic-ferrimagnetic complex.

As shown in FIG. 4, the coercive force is increased by exchange coupling at the time of forming the antiferromagnetic-ferrimagnetic composite as compared with the hexaferrite powder.

As described above, in the composite magnetic sheet of the first embodiment, (100) can control the directional magnetic anisotropy by adjusting the arrangement pattern of the antiferromagnetic layer and the ferrimagnetic layer, and thereby has a resonant frequency increasing effect.

Thus, the composite magnetic sheet 100 can increase the coercive force to increase the resonance frequency by a relatively simple method of forming the pattern 110 at the bonding interface of the antiferromagnetic layer and the ferromagnetic layer without changing the lattice structure of the magnetic material Therefore, it is possible to reduce the research cost while it is easy to manufacture.

The composite magnetic sheet 100 includes a polymer matrix 120 for fixing the pattern 110. The material of the polymer matrix 120 may be any known binder material without limitation. For example, the thermoplastic resin a thermoplastic resin or a thermosetting resin may be used.

The composite magnetic sheet 100 having such a structure is produced by pouring a slurry obtained by mixing a ferrite material or an antiferromagnetic material with a binder or the like into a cylindrical molding die, followed by drying and separation processes to prepare a core 110a. Separately, Or a slurry obtained by mixing an antiferromagnetic material with a binder or the like is coated in a plate form by a doctor blade method or the like and then dried to produce a multilayer sheet in which an antiferromagnetic layer and a ferrimagnetic layer are alternately laminated, A multilayer sheet is attached to the outer circumferential surface to form a coaxial pattern of the structure of the core 110a to shell 110b and the pattern is buried in a direction perpendicular to the polymer matrix 120 and then cooled to a low temperature It can be manufactured by heat treatment.

The composite magnetic sheet 100 thus fabricated is made of a micro-sheet having a density of about 4.3 or less including a binder in the core 110a and the shell 110b and has a flexible property, The present invention is applicable to the production of a magnetic material of an electronic part which is required.

In addition, the composite magnetic sheet 100 may be manufactured as a sintered sheet through a sintering process instead of the low-temperature heat treatment described above. In this case, the core 110a and the shell 110b do not contain a binder.

5 is a cross-sectional view of a composite magnetic sheet according to a second embodiment of the present invention.

5, the composite magnetic sheet 200 according to the second embodiment of the present invention includes a first layer 210 and a second layer 220 stacked on and under, and a first layer 210 And a concave-convex pattern 230 formed on a bonding interface between the first layer 220 and the second layer 220. [

In the second embodiment of the present invention, the second layer 220 and the first layer 210 are stacked on top and bottom, a concave-convex pattern 230 is formed on these interfaces, and a structure in which a polymer matrix is not formed The materials of the first layer 210 and the second layer 220 may be the same as those of the core 110a and the shell 110b of the first embodiment of the present invention. Therefore, the description of the constituent elements of the second embodiment of the present invention that is the same as the second embodiment of the present invention will be omitted, and only differences will be described.

Here, the first layer 210 is formed of an antiferromagnetic layer or a ferrimagnetic layer, and the second layer 220 is formed of an antiferromagnetic layer or a ferrimagnetic layer having a magnetic property different from that of the first layer 210.

For example, when the first layer 210 is formed of an antiferromagnetic layer, the second layer 220 is formed of a ferrimagnetic layer. When the first layer 210 is formed of a ferrimagnetic layer, .

1, the antiferromagnetic layer may be formed comprising an antiferromagnetic material having a knee temperature of about 300K or more, such as NiO or Cr, and the ferrimagnetic layer may be formed of a hexaferrite material, preferably a Y type or Z type hexaferrite And the like.

The concavo-convex pattern 230 formed on the bonding interface between the first layer 210 and the second layer 220 has a concave portion 230a and a convex portion 230b with respect to the first layer 210, portion 230b. The concave portion 230a of the first layer 210 corresponds to the convex portion of the second layer 220 and the convex portion 230b of the first layer 210 corresponds to the concave portion of the second layer 220 And corresponds to the concave portion (not shown).

In the second embodiment of the present invention, the concavo-convex pattern 230 plays a role of widening the area (contact area) between the antiferromagnetic layer and the ferromagnetic layer per unit volume as in the coaxial pattern 110 of FIG.

Therefore, the composite magnetic sheet 200 according to the second embodiment of the present invention can obtain the effect of increasing the resonance frequency by increasing the coercive force in the same manner as the composite magnetic sheet 100 of the first embodiment of the present invention, The high permeability and low investment loss characteristics can be satisfied at the same time.

At this time, it is possible to control the magnetic anisotropy in the plane direction by adjusting the arrangement pattern of the antiferromagnetic layer and the ferrimagnetic layer, thereby increasing the resonance frequency.

The composite magnetic sheet 200 having such a structure is prepared by coating a slurry obtained by mixing a ferrite material or an antiferromagnetic material with a binder or the like in a plate form by a doctor blade method or the like and drying the two sheets, Pressing the sheet by a press to form a concave / convex pattern 230 on the sheet, stacking the two sheets 210 and 220 having concave and convex patterns so as to be fitted to each other, and then performing heat treatment at a low temperature (about 100 to 150 ° C).

The composite magnetic sheet 200 produced in this manner is made of a micro-sheet having a density of about 4.3 or less and contains a binder in the first layer 210 and the second layer 220, and has excellent moldability because it has a flexible property .

The composite magnetic sheet 200 may be manufactured as a sintered sheet through a sintering process instead of the low temperature heat treatment described above. In this case, the first layer 210 and the second layer 220 do not contain a binder.

In the composite magnetic sheets 100 and 200 of the first and second embodiments of the present invention, the patterns 110 and 230 capable of widening the total area between the antiferromagnetic layer and the ferromagnetic layer per unit volume are included, High permeability and low investment loss characteristics can be satisfied at the same time.

As a result, the composite magnetic sheets 100 and 200 of this embodiment are suitable for mounting as a component constituting a magnetic-field antenna of a portable communication apparatus. In this case, it is possible to fabricate a magnetic antenna that simultaneously satisfies both miniaturization, high efficiency, and wide band characteristics in a high frequency band of 1 GHz or more.

On the other hand, it goes without saying that the magnetic substance antenna provided with the composite magnetic sheets 100 and 200 of the present embodiment can be used in combination with electronic devices mounted on automobiles, household appliances, etc., as well as communication devices such as cellular phones and wireless LANs.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, and that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention. However, it should be understood that such substitutions, changes, and the like fall within the scope of the following claims.

100, 200: composite magnetic sheet 110, 230: pattern
110a: core 110b: shell
120: polymer matrix 210: first layer
220: second layer 230a: concave portion
230b:

Claims (16)

Wherein the antiferromagnetic layer and the ferrimagnetic layer are in contact with each other, and the pattern includes a bonding interface between the antiferromagnetic layer and the ferrimagnetic layer.
The method according to claim 1,
Wherein the ferromagnetic layer comprises a hexagonal ferrite material.
3. The method of claim 2,
Wherein the hexaferrite material is Y type or Z type.
The method according to claim 1,
The antiferromagnetic layer
A composite magnetic sheet comprising an antiferromagnetic material having a Neel temperature of 300K or more.
5. The method of claim 4,
Wherein the antiferromagnetic layer comprises at least NiO or Cr.
The method according to claim 1,
Wherein the pattern is a concavo-convex shape.
The method according to claim 1,
The pattern
Wherein the first magnetic pole layer is arranged in a direction perpendicular to the upper surface of the composite magnetic sheet,
Wherein the antiferromagnetic layer and the ferromagnetic layer are coaxially arranged in a core-shell structure in which alternating layers are laminated.
8. The method of claim 7,
The coaxial type of core-
The core being a columnar member having a predetermined shape, and at least one or more shells surrounding an outer circumferential surface of the core,
Wherein the core is formed of one of the antiferromagnetic layer and the ferromagnetic layer.
9. The method of claim 8,
Wherein the core is prismatic or cylindrical.
9. The method of claim 8,
The composite magnetic sheet
And a polymer matrix for fixing the pattern.
The method according to claim 1,
The composite magnetic sheet
And the planar magnetic anisotropy is controlled by the arrangement of the patterns.
The method according to claim 1,
Wherein the composite magnetic sheet has a flexible property.
13. The method of claim 12,
Wherein the composite magnetic sheet has a density of 4.3 or less.
14. The method of claim 13,
Wherein the antiferromagnetic layer and the ferrimagnetic layer further comprise a binder.
The method according to claim 1,
Wherein the composite magnetic sheet is a sintered body.
A magnetic material antenna using the composite magnetic sheet according to any one of claims 1 to 15.

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