JP2006310369A - Magnetic material and magnetic device - Google Patents

Magnetic material and magnetic device Download PDF

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JP2006310369A
JP2006310369A JP2005127907A JP2005127907A JP2006310369A JP 2006310369 A JP2006310369 A JP 2006310369A JP 2005127907 A JP2005127907 A JP 2005127907A JP 2005127907 A JP2005127907 A JP 2005127907A JP 2006310369 A JP2006310369 A JP 2006310369A
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magnetic
frequency
permeability
resonance frequency
magnetic material
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Ken Takahashi
高橋　　研
Tomoyuki Ogawa
智之 小川
Hajime Shinohara
肇 篠原
Daiji Hasegawa
大二 長谷川
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INST OF FUNCTIONAL MATERIALS S
INSTITUTE OF FUNCTIONAL MATERIALS SCIENCE Inc
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INSTITUTE OF FUNCTIONAL MATERIALS SCIENCE Inc
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic material that prevents real permeability from decreasing by a blocking resonance frequency in a low-frequency region as compared with a ferromagnetic resonance frequency, and has high permeability at a high-frequency band; and to provide a method of manufacturing the magnetic material, and a magnetic device using the magnetic material. <P>SOLUTION: The magnetic material used for the magnetic device for high-frequency bands is set to be a magnetic particulate comprising a nano particle. In this case, the blocking resonance frequency of the magnetic particulate is set to be the same as, or larger than the ferromagnetic resonance frequency of the magnetic particulate. For example, the magnetic particulate is the nano particle of Fe<SB>3</SB>O<SB>4</SB>, and has super paramagnetism. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、通信、放送、IT機器などの高周波部品や回路等に用いられる高周波用の磁性材料とその製造方法、並びに前記磁性材料を用いた磁気デバイスに関する。   The present invention relates to a high-frequency magnetic material used for high-frequency components and circuits such as communication, broadcasting, and IT equipment, a manufacturing method thereof, and a magnetic device using the magnetic material.

近年、個人用携帯機器や移動通信の発展に伴い、これらの機器に用いられる磁気デバイスの一層の小型化および低価格化とＧＨｚを超える高帯域化が技術潮流になっており、画期的な高周波用の磁性材料の出現が期待されている。   In recent years, with the development of personal portable devices and mobile communications, the technological trend has been to further reduce the size and price of magnetic devices used in these devices and to increase the bandwidth beyond GHz. The appearance of magnetic materials for high frequencies is expected.

高周波用磁性材料としては、従来、Mn-ZnフェライトやNi-Znフェライト等が用いられていたが、これらの材料の使用周波数範囲は、せいぜい数ＭＨzから数100ＭＨz程度であった。しかしながら、携帯電話のような通信機器の場合、現在、周波数１ＧＨｚ前後（０．８〜１．８ＧＨｚ）が主流であり、最近の各種通信機器に用いられる磁性材料は、１ＧＨzもしくはそれ以上まで使用できる材料が求められている。   Conventionally, Mn—Zn ferrite, Ni—Zn ferrite, and the like have been used as high-frequency magnetic materials. However, the frequency range of use of these materials is at most about several MHz to several hundred MHz. However, in the case of communication devices such as mobile phones, the frequency is currently around 1 GHz (0.8 to 1.8 GHz), and magnetic materials used in various recent communication devices can be used up to 1 GHz or more. There is a need for materials.

ところで、従来から用いられている磁性材料は、磁性材料の透磁率（μ）と強磁性共鳴周波数（fr）の間に、μ・fr＝一定なる関係があり、μの大きな材料は共鳴周波数が低くなり、μの小さな材料は共鳴周波数が高くなる。そして、共鳴周波数より高い周波数で透磁率は減少してしまう。例えば、これらの材料では、１GHｚでは透磁率は１に近くなり、磁性材料としての充分な役割を果たすことが出来ない。（非特許文献１参照）。 By the way, the magnetic material used conventionally has a relationship of μ · f r = constant between the magnetic permeability (μ) and the ferromagnetic resonance frequency (f r ), and a material with a large μ is resonant. The frequency decreases, and the material with a small μ increases the resonance frequency. Then, the magnetic permeability decreases at a frequency higher than the resonance frequency. For example, in these materials, the magnetic permeability is close to 1 at 1 GHz and cannot play a sufficient role as a magnetic material. (Refer nonpatent literature 1).

ところで、周波数特性を含む磁気特性向上のために、磁性材料を微粒子化することが研究開発されているが、磁性材料を微粒子化することにより、強磁性共鳴周波数frとともに、微粒子特有のブロッキング共鳴周波数fbが存在する問題がある。即ち、一軸性の単磁区ナノ粒子はアップスピン状態とダウンスピン状態とがあり、遷移する時間、即ち緩和時間τは、τ＝τ0exp（ＫuＶ／ｋBＴ）で表され、磁気異方性定数Ｋuやナノ粒子の体積Ｖで決まる。なお、上記式中のｋBはボルツマン定数、Ｔは絶対温度である。交流磁場中（高周波中）では、緩和時間の逆数の周波数で共鳴を起し、その周波数以上で、透磁率は急激に減少する問題がある（非特許文献２参照）。
近角 聰信著、強磁性体の物理（下）、第１３版、株式会社裳華房、2003年3月25日発行、319〜326頁 C. P. Bean and J. D. Livingston, "Superparamagnetism", Journal of Applied Physics Supplement to Vol. 30, No. 4, 120S (1959) Meanwhile, for improving magnetic characteristics including the frequency characteristics, although the magnetic material to be micronized is research and development, by fine particles of magnetic material, together with the ferromagnetic resonance frequency f r, the particle specific blocking resonance There is a problem that the frequency f b exists. That is, uniaxial single domain nanoparticles have an up-spin state and a down-spin state, and the transition time, that is, the relaxation time τ is expressed by τ = τ 0 exp (K u V / k B T) It is determined by the anisotropy constant Ku and the volume V of the nanoparticles. In the above formula, k B is a Boltzmann constant, and T is an absolute temperature. In an alternating magnetic field (in a high frequency), resonance occurs at a frequency that is the reciprocal of the relaxation time, and there is a problem that the magnetic permeability rapidly decreases above that frequency (see Non-Patent Document 2).
Konnobu Nobunobu, Physics of Ferromagnetic Material (bottom), 13th edition, Hankabo Co., Ltd., published on March 25, 2003, pages 319-326 CP Bean and JD Livingston, "Superparamagnetism", Journal of Applied Physics Supplement to Vol. 30, No. 4, 120S (1959)

この発明は上記の点に鑑みてなされたもので、この発明の課題は、強磁性共鳴周波数より低い周波数領域において、ブロッキング共鳴周波数によって実数透磁率が低下することがなく、高い周波数帯域において高い透磁率を有する磁性材料、並びに前記磁性材料を用いた磁気デバイスを提供することにある。   The present invention has been made in view of the above points, and an object of the present invention is to prevent a real permeability from being lowered by a blocking resonance frequency in a frequency region lower than a ferromagnetic resonance frequency, and to provide a high permeability in a high frequency band. It is an object of the present invention to provide a magnetic material having magnetic susceptibility and a magnetic device using the magnetic material.

上記課題は、以下により達成される。即ち、ナノ粒子からなる磁性微粒子であって、前記磁性微粒子のブロッキング共鳴周波数が、前記磁性微粒子の強磁性共鳴周波数と同じか、或いは大きいことを特徴とする（請求項１）。また、前記請求項１に記載の磁性材料において、前記磁性微粒子は超常磁性を有するものとする（請求項２）。上記磁性微粒子としては、詳細は後述するように、例えば平均粒径１５nm以下のFe3O4粒子とする。 The above-mentioned subject is achieved by the following. That is, the magnetic fine particles are made of nanoparticles, and the blocking resonance frequency of the magnetic fine particles is the same as or higher than the ferromagnetic resonance frequency of the magnetic fine particles (claim 1). Further, in the magnetic material according to claim 1, the magnetic fine particles have superparamagnetism (claim 2). The magnetic fine particles are, for example, Fe 3 O 4 particles having an average particle diameter of 15 nm or less, as will be described in detail later.

さらに、磁気デバイスの発明としては、前記請求項１または２に記載の磁性材料を、誘電体材料中に分散したものとする（請求項３）。磁気デバイスとして、例えば配線基板を考えた場合、高い透磁率と共に、低い誘電率を備える必要がある。この場合、低い誘電率を備えた誘電体、例えば、ポリテトラフルオロエチレンやポリプロピレン、ポリエステル、ポリイミド、エポキシ樹脂等の電機絶縁性の樹脂中に、前記磁性材料を分散させた磁気デバイスとすることが好ましい。誘電体としては、樹脂材料の他に各種のセラミックが使用できる。   Furthermore, as invention of a magnetic device, the magnetic material of the said Claim 1 or 2 shall be disperse | distributed in the dielectric material (Claim 3). For example, when considering a wiring board as a magnetic device, it is necessary to provide a low dielectric constant with a high magnetic permeability. In this case, a magnetic device in which the magnetic material is dispersed in a dielectric having a low dielectric constant, for example, an electrical insulating resin such as polytetrafluoroethylene, polypropylene, polyester, polyimide, or epoxy resin. preferable. As the dielectric, various ceramics can be used in addition to the resin material.

この発明によれば、強磁性共鳴周波数より低い周波数領域において、ブロッキング共鳴周波数によって実数透磁率が低下することがなく、高い周波数帯域において高い透磁率を有する磁性材料が提供できる。また、前記のような磁気デバイスに適用した場合の実用上の効果は極めて大きい。以下に、この発明に係る磁性材料の作用効果を含む技術的意義について詳述する。   According to the present invention, in the frequency region lower than the ferromagnetic resonance frequency, the magnetic permeability having high permeability in the high frequency band can be provided without the real permeability being lowered by the blocking resonance frequency. Further, the practical effect when applied to the magnetic device as described above is extremely large. The technical significance including the effects of the magnetic material according to the present invention will be described in detail below.

一般にブロッキング共鳴周波数fbは、材料の磁気異方性定数Ｋuおよびナノ粒子体積Ｖ、温度Ｔで決まり、ブロッキング共鳴周波数fb＝ｆ0exp（−ＫuＶ／ｋBＴ）と表わされる。ここで、ｆ0は定数である。また、強磁性共鳴周波数frは、fr＝γHk/2πと表わされる。ここでHkは材料の異方性磁界、γはジャイロ磁気定数をあらわす。 In general, the blocking resonance frequency f b is determined by the magnetic anisotropy constant K u of the material, the nanoparticle volume V, and the temperature T, and is expressed as blocking resonance frequency f b = f 0 exp (−K u V / k B T). . Here, f 0 is a constant. The ferromagnetic resonance frequency f r is expressed as f r = γH k / 2π. Here, H k represents the anisotropic magnetic field of the material, and γ represents the gyro magnetic constant.

ところで、一般にブロッキング共鳴周波数fbは、前述のように強磁性共鳴周波数fr以下であり、この周波数以上では、透磁率は大幅に減衰する。しかしながら、fb≧frとなるように材料の磁気異方性定数Ｋuおよびナノ粒子体積Ｖを選定することにより、透磁率を強磁性共鳴周波数まで高く維持できる。微粒子を詳細に検討した結果、特定の粒径以下にナノ粒子化すると、ブロッキング共鳴周波数は強磁性共鳴周波数以上となり、強磁性共鳴周波数まで透磁率は大きく、結果的に高い周波数まで高い透磁率を示し、優れた高周波特性を示すことができることが判明した。この発明は、上記原理を利用することにより、優れた高周波磁性材料を提供することができるようにした点に特徴がある。 Incidentally, generally blocking the resonance frequency f b, or less ferromagnetic resonance frequency f r as described above, in this frequency or higher, the permeability is greatly attenuated. However, by selecting the f b ≧ f r become like magnetic anisotropy constant K u and nanoparticles volume V materials can maintain high permeability to the ferromagnetic resonance frequency. As a result of examining fine particles in detail, when nano-particles are produced below a specific particle size, the blocking resonance frequency becomes equal to or higher than the ferromagnetic resonance frequency, and the magnetic permeability is large up to the ferromagnetic resonance frequency, resulting in high permeability up to a high frequency. It has been shown that excellent high frequency characteristics can be exhibited. The present invention is characterized in that an excellent high-frequency magnetic material can be provided by utilizing the above principle.

図１は上記原理を模式的に説明する図であり、縦軸上段の実数透磁率（μダッシュ）および縦軸下段の虚数透磁率（μツーダッシュ）と、横軸の周波数ｆ(Hz)との関係を示す。図１（ａ）はこの発明に係り、fb≧frとなる場合の粒径が小さい材料の透磁率の周波数依存性を模式的に示す図であり、図１（ｂ）は従来の磁性材料に係り、粒径の比較的大きな磁性材料の透磁率の周波数依存性を模式的に示す図である。 FIG. 1 is a diagram schematically illustrating the above principle. The real permeability (μ dash) on the upper vertical axis, the imaginary permeability (μ to dash) on the lower vertical axis, and the frequency f (Hz) on the horizontal axis. The relationship is shown. FIGS. 1 (a) relates to the present invention, is a view schematically showing the frequency dependence of the permeability of small particle size material when the f b ≧ f r, 1 (b) is a conventional magnetic It is a figure which shows typically the frequency dependence of the magnetic permeability of a magnetic material with a comparatively big particle size concerning a material.

従来は、図１（ｂ）に示すように、実数透磁率はブロッキング共鳴周波数fb以上で大幅に減衰して略１に近づくのに対して、この発明によれば、図１（ａ）に示すようにfb≧frとなるので、強磁性共鳴周波数frより低い周波数領域において、ブロッキング共鳴周波数によって実数透磁率が低下することがなく、透磁率の周波数特性の向上を図ることができる。詳細は、実施例に基づき後述する。 Conventionally, as shown in FIG. 1 (b), the real permeability greatly attenuated by blocking the resonant frequency f b or against approaching approximately 1, according to the present invention, in FIGS. 1 (a) since the f b ≧ f r as shown, it is possible to achieve in the lower frequency range than the ferromagnetic resonance frequency f r, without real permeability decreases due to the blocking resonance frequencies, the improvement in the frequency characteristics of the permeability . Details will be described later based on an embodiment.

次に、この発明の実施形態に関して、実施例および比較例に基いて説明する。なお、後述する飽和磁化の単位emu/ccをＳＩ単位に変換する場合には、１emu/cc＝0.0012566Wb/m2により換算すればよい。 Next, embodiments of the present invention will be described based on examples and comparative examples. In addition, when converting the unit of saturation magnetization emu / cc, which will be described later, into an SI unit, it may be converted by 1 emu / cc = 0.0012566 Wb / m 2 .

（実施例）
５００ｃｃのフラスコを用い、室温のオクチルエーテル（溶媒）200ml中に原料となる鉄カルボニルFe(CO)5 0.4 mol、界面活性剤となるオレイン酸0.2 molを入れ、その後スターラーで400 rpmで攪拌しながらマントルヒーターで昇温し、287℃で2時間保持した。その後、フラスコをマントルヒーターから外し、自然冷却を行い溶液の温度を室温まで下げた。Fe3O4ナノ粒子を含む合成溶液にアセトンを注入し、遠心分離機で洗浄を行うことで未反応物などを除去した。電子顕微鏡観察結果対数正規分布関数を用いて粒度分布を評価すると、平均粒径8.8nm、粒径分散2.2nmが得られた（以下、実施例試料という。）。 (Example)
Using a 500 cc flask, put 0.4 mol of iron carbonyl Fe (CO) 5 mol as a raw material and 0.2 mol of oleic acid as a surfactant in 200 ml of octyl ether (solvent) at room temperature, and then stirring with a stirrer at 400 rpm The temperature was raised with a mantle heater and held at 287 ° C. for 2 hours. Thereafter, the flask was removed from the mantle heater, naturally cooled, and the temperature of the solution was lowered to room temperature. Acetone was injected into the synthesis solution containing Fe 3 O 4 nanoparticles, and unreacted substances were removed by washing with a centrifuge. Electron microscope observation results When the particle size distribution was evaluated using a lognormal distribution function, an average particle size of 8.8 nm and a particle size dispersion of 2.2 nm were obtained (hereinafter referred to as Example samples).

（比較例）
５００ｃｃのフラスコを用い、室温のオクチルエーテル（溶媒）100ml中に原料となる鉄カルボニルFe(CO)5 0.2 mol、界面活性剤となるオレイン酸0.1 molを入れ、その後スターラーで400 rpmで攪拌しながらマントルヒーターで昇温し、287℃で2時間保持した。その後、フラスコをマントルヒーターから外し、自然冷却を行い溶液の温度を室温まで下げた。Fe3O4ナノ粒子を含む合成溶液にアセトンを注入し、遠心分離機で洗浄を行うことで未反応物などを除去した。電子顕微鏡観察結果対数正規分布関数を用いて粒度分布を評価すると、平均粒径17.2nm 、粒径分散4.1nmが得られた（以下、比較例試料という。）。 (Comparative example)
Using a 500 cc flask, put 0.2 mol of iron carbonyl Fe (CO) 5 as a raw material and 0.1 mol of oleic acid as a surfactant in 100 ml of octyl ether (solvent) at room temperature, and then stirring with a stirrer at 400 rpm The temperature was raised with a mantle heater and held at 287 ° C. for 2 hours. Thereafter, the flask was removed from the mantle heater, naturally cooled, and the temperature of the solution was lowered to room temperature. Acetone was injected into the synthesis solution containing Fe 3 O 4 nanoparticles, and unreacted substances were removed by washing with a centrifuge. Electron microscope observation results When the particle size distribution was evaluated using a lognormal distribution function, an average particle size of 17.2 nm and a particle size dispersion of 4.1 nm were obtained (hereinafter referred to as a comparative sample).

図２は上記実施例試料および比較例試料の電子顕微鏡写真を示す。また、図３は、実施例試料および比較例試料の粒径分布を示す図である。図２および図３において、それぞれ（ａ）は実施例試料に係るもの、（ｂ）は比較例試料に係るものを示す。なお、図３（ａ）および（ｂ）において、平均粒径はＤave、粒径分散はＷで示し、Ｗ／Ｄaveは、それぞれ0.25および0.24であった。 FIG. 2 shows electron micrographs of the above-described example samples and comparative example samples. Moreover, FIG. 3 is a figure which shows the particle size distribution of an Example sample and a comparative example sample. 2 and 3, (a) shows a sample related to the example sample, and (b) shows a sample related to the comparative sample. In FIGS. 3A and 3B, the average particle diameter is D ave , the particle diameter dispersion is W, and W / D ave is 0.25 and 0.24, respectively.

次に、図４について述べる。図４は上記実施例試料および比較例試料のX線回折図を示す。図４のように、マグネタイトに起因する回折線のみが得られた。以上により、実施例試料は、非常に均一なマグネタイト単相のナノ粒子であることが分かる。   Next, FIG. 4 will be described. FIG. 4 shows X-ray diffraction patterns of the above-described example samples and comparative example samples. As shown in FIG. 4, only the diffraction lines attributed to magnetite were obtained. From the above, it can be seen that the example samples are extremely uniform magnetite single-phase nanoparticles.

次に、マグネタイト微粒子集合体の作製を行なった。図５は、マグネタイト微粒子集合体の作製手順およびその構成の説明図である。図５に示すように、前述のように作製したマグネタイト微粒子を高分子ポリマー（ポリビニルピロリドン（PVP））、クロロホルム、トルエンとよく混ぜ合わせ（粒子充填率10〜20％）、シャーレに移し、試料厚さを約300μmとして、大気中で７０℃で６時間乾燥させたものを5mm×5mｍの大きさに切り出した。   Next, a magnetite fine particle aggregate was produced. FIG. 5 is an explanatory diagram of a procedure for producing a magnetite fine particle aggregate and its configuration. As shown in FIG. 5, the magnetite fine particles prepared as described above are mixed well with a polymer (polyvinylpyrrolidone (PVP)), chloroform, and toluene (particle filling rate: 10 to 20%), transferred to a petri dish, and sample thickness A thickness of about 300 μm was dried in the air at 70 ° C. for 6 hours, and cut into a size of 5 mm × 5 mm.

次に、上記のように作製した集合体について、振動試料型磁気測定装置（VSM）で磁化特性の測定を行った。その結果を図６に示す。図６によれば、平均粒径8.8nm（実施例）および17.2nm（比較例）の両試料において、室温でヒステリシスループは観測されなかった。これはマグネタイト微粒子が超常磁性を示している事を示唆する。また、飽和磁化の値は8.8nmの試料で255emu/cc、17.2nmの試料で294emu/ccであった。   Next, the magnetic properties of the aggregate produced as described above were measured using a vibrating sample magnetometer (VSM). The result is shown in FIG. According to FIG. 6, no hysteresis loop was observed at room temperature in both samples having an average particle diameter of 8.8 nm (Example) and 17.2 nm (Comparative Example). This suggests that the magnetite fine particles show superparamagnetism. The saturation magnetization was 255 emu / cc for the 8.8 nm sample and 294 emu / cc for the 17.2 nm sample.

次に、平均粒径8.8 nm（実施例）および17.2 nm（比較例）の両試料に対し、外部磁場がゼロのときの複素透磁率の周波数特性の測定を行った。図７にその結果を示す。図７によれば、17.2 nm（比較例）では、実数透磁率（μダッシュ）は106 Hz以上で周波数の増大に伴いなだらかに減少し、約2×109 Hz（約２GHz）で急激に減少する。虚数透磁率（μツーダッシュ）は略106Hz付近でブロードなピークを示し、約4×109Hzでピークを示す。また、外部磁場印加中における複素透磁率測定から、虚数透磁率の106 Hz付近のピークは消失し、4×109 Hzのピーク位置は外部磁場の大きさに比例して高周波側にシフトする。これらの結果の特徴から、外部磁場がゼロのときの106 Hz付近における実数透磁率の減少および虚数透磁率のブロードなピークはブロッキング共鳴によるもの、また、2×109 Hzにおける実数透磁率の急激な減少および虚数透磁率の前記ピークは自然共鳴によるものと考えられる（前記図１（ｂ）参照）。 Next, frequency characteristics of the complex permeability when the external magnetic field was zero were measured for both samples having an average particle diameter of 8.8 nm (Example) and 17.2 nm (Comparative Example). FIG. 7 shows the result. According to Fig. 7, at 17.2 nm (comparative example), the real permeability (μ dash) gradually decreases with increasing frequency at 10 6 Hz or more, and rapidly at about 2 × 10 9 Hz (about 2 GHz). Decrease. The imaginary permeability (μ to dash) shows a broad peak around 10 6 Hz and a peak at about 4 × 10 9 Hz. In addition, from the complex permeability measurement during external magnetic field application, the peak of imaginary permeability near 10 6 Hz disappears, and the peak position of 4 × 10 9 Hz shifts to the high frequency side in proportion to the magnitude of the external magnetic field. . From the characteristics of these results, the decrease in the real permeability near 10 6 Hz when the external magnetic field is zero and the broad peak of the imaginary permeability are due to blocking resonance, and the real permeability at 2 × 10 9 Hz The sudden decrease and the peak of the imaginary permeability are considered to be due to natural resonance (see FIG. 1B).

一方、平均粒径8.8 nm（実施例）の試料では、外部磁場がゼロのとき、実数透磁率は1×109 Hz（約１GHz）程度まで一定値（５強の値）を示し、それ以上では周波数の増加と共に、17.2 nmに比べて比較的緩やかに減少する。また、虚数透磁率は6×109 Hz付近でピークを示した。外部磁場の増加に比例して虚数透磁率のピーク位置は高周波側にシフトした。これらの結果の特徴から、外部磁場がゼロのときの1×109 Hz以上における実数透磁率の減少および虚数透磁率のピークは自然共鳴によるものと考えられ、強磁性共鳴周波数fr以下の周波数領域においてブロッキング共鳴周波数fbは観測されていないことが分かる（前記図１（ａ）参照）。 On the other hand, in the sample with an average particle size of 8.8 nm (Example), when the external magnetic field is zero, the real permeability shows a constant value (a value of slightly over 5) up to about 1 × 10 9 Hz (about 1 GHz), and more Then, as the frequency increases, it decreases relatively slowly compared to 17.2 nm. Moreover, the imaginary permeability showed a peak around 6 × 10 9 Hz. The peak position of the imaginary permeability shifted to the high frequency side in proportion to the increase of the external magnetic field. From the characteristics of these results, reduction and peak imaginary permeability real permeability at 1 × 10 9 Hz or more when the external magnetic field is zero is considered to be due to natural resonance, ferromagnetic resonance frequency f r the following frequencies It can be seen that the blocking resonance frequency f b is not observed in the region (see FIG. 1A).

ちなみに、虚数透磁率のピーク位置の外部磁場依存性において外部磁場ゼロの切片から得られる自然共鳴周波数から、前述の式fr＝γHk/2πを用いて算出される異方性磁場の値、静磁気特性から得られた飽和磁化および電子顕微鏡から観察された粒径を用いてブロッキング共鳴周波数fbを推算すると、ブロッキング共鳴周波数fb＝ｆ0exp（−ＫuＶ／ｋBＴ）における定数ｆ0＝10GHzで、fb＝6.8GHzとなり、fr＜fbを満たすことが確認された。 By the way, from the natural resonance frequency obtained from the intercept of the external magnetic field zero in the external magnetic field dependence of the peak position of the imaginary permeability, the value of the anisotropic magnetic field calculated using the above-described formula f r = γH k / 2π, When the blocking resonance frequency f b is estimated using the saturation magnetization obtained from the magnetostatic characteristics and the particle diameter observed from the electron microscope, the blocking resonance frequency f b = f 0 exp (−K u V / k B T) It was confirmed that the constant f 0 = 10 GHz, f b = 6.8 GHz, and f r <f b was satisfied.

以上のように、Fe3O4ナノ粒子の粒径を小さくすることでブロッキング共鳴周波数を強磁性共鳴周波数近傍またはそれ以上に高めることにより、GHz帯域における高周波領域まで高透磁率を得ることが可能となった。 As described above, by reducing the particle size of Fe 3 O 4 nanoparticles, it is possible to obtain high magnetic permeability up to the high frequency region in the GHz band by increasing the blocking resonance frequency to near or above the ferromagnetic resonance frequency. It became.

本発明に係る透磁率の周波数特性について従来と比較して模式的に示す説明図。Explanatory drawing which shows typically the frequency characteristic of the magnetic permeability which concerns on this invention compared with the past. 本発明に係る実施例及び比較例試料の電子顕微鏡写真。The electron micrograph of the Example which concerns on this invention, and a comparative example sample. 本発明に係る実施例及び比較例試料の粒径分布を示す図。The figure which shows the particle size distribution of the Example which concerns on this invention, and a comparative example sample. 本発明に係る実施例及び比較例試料のX線回折図。The X-ray-diffraction figure of the Example and comparative example sample which concern on this invention. 本発明に係るマグネタイト微粒子集合体の作製手順およびその構成の説明図。Explanatory drawing of the preparation procedure of the magnetite fine particle aggregate | assembly which concerns on this invention, and its structure. 本発明に係る実施例及び比較例試料の磁化特性の測定結果を示す図。The figure which shows the measurement result of the magnetization characteristic of the Example which concerns on this invention, and a comparative example sample. 本発明に係る実施例及び比較例試料の複素透磁率の周波数特性の測定結果を示す図。The figure which shows the measurement result of the frequency characteristic of the complex magnetic permeability of the Example which concerns on this invention, and a comparative example sample.

Claims (3)

ナノ粒子からなる磁性微粒子であって、前記磁性微粒子のブロッキング共鳴周波数が、前記磁性微粒子の強磁性共鳴周波数と同じか、或いは大きいことを特徴とする磁性材料。   A magnetic fine particle comprising nanoparticles, wherein the magnetic fine particle has a blocking resonance frequency equal to or higher than a ferromagnetic resonance frequency of the magnetic fine particle. 請求項１に記載の磁性材料において、前記磁性微粒子は超常磁性を有することを特徴とする磁性材料。   The magnetic material according to claim 1, wherein the magnetic fine particles have superparamagnetism. 前記請求項１または２に記載の磁性材料を、誘電体材料中に分散したことを特徴とする磁気デバイス。

3. A magnetic device, wherein the magnetic material according to claim 1 is dispersed in a dielectric material.

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