JP4921897B2 - Magnetic sensor - Google Patents

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JP4921897B2
JP4921897B2 JP2006240377A JP2006240377A JP4921897B2 JP 4921897 B2 JP4921897 B2 JP 4921897B2 JP 2006240377 A JP2006240377 A JP 2006240377A JP 2006240377 A JP2006240377 A JP 2006240377A JP 4921897 B2 JP4921897 B2 JP 4921897B2
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利江 佐藤
究 工藤
公一 水島
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Description

本発明は高密度磁気記録における読み出し用磁気ヘッドなどに応用される磁気センサーに関する。   The present invention relates to a magnetic sensor applied to a read magnetic head or the like in high-density magnetic recording.

巨大磁気抵抗効果（ＧＭＲ効果）を利用したＧＭＲヘッドの登場以来、磁気記録の記録密度は、年率１００％で向上している。ＧＭＲ素子は、強磁性層／非磁性金属層／強磁性層のサンドイッチ構造の積層膜からなる。ＧＭＲ素子は、一方の強磁性層に交換バイアスを及ぼして磁化を固定し、他方の強磁性層の磁化方向を外部磁界により変化させ、２つの強磁性層の磁化方向の相対角度の変化を抵抗値の変化として検出する、いわゆるスピンバルブ膜の磁気抵抗効果を利用した素子である。スピンバルブ膜の膜面に電流を流し、抵抗変化を検出するＣＩＰ−ＧＭＲ素子と、スピンバルブ膜の膜面に垂直に電流を流し抵抗変化を検出するＣＰＰ−ＧＭＲ素子が開発されている。その磁気抵抗比（ＭＲ比）はＣＩＰ−ＧＭＲ素子、ＣＰＰ−ＧＭＲ素子とも数％程度であり、２００Ｇｂｉｔ／ｉｎｃｈ2程度の記録密度まで対応可能であろうと考えられている。 Since the advent of GMR heads using the giant magnetoresistive effect (GMR effect), the recording density of magnetic recording has improved at an annual rate of 100%. The GMR element is composed of a laminated film having a sandwich structure of ferromagnetic layer / nonmagnetic metal layer / ferromagnetic layer. The GMR element applies an exchange bias to one ferromagnetic layer to fix the magnetization, changes the magnetization direction of the other ferromagnetic layer by an external magnetic field, and resists a change in the relative angle between the magnetization directions of the two ferromagnetic layers. It is an element that utilizes the magnetoresistive effect of a so-called spin valve film that is detected as a change in value. A CIP-GMR element that detects a change in resistance by flowing a current through the film surface of the spin valve film and a CPP-GMR element that detects a change in resistance by flowing a current perpendicular to the film surface of the spin valve film have been developed. The magnetoresistance ratio (MR ratio) of both the CIP-GMR element and the CPP-GMR element is about several percent, and it is considered that a recording density of about 200 Gbit / inch 2 can be handled.

より高密度な磁気記録に対応するため、トンネル磁気抵抗効果（ＴＭＲ効果）を利用したＴＭＲ素子の開発が進められている。ＴＭＲ素子は強磁性層／非磁性絶縁層／強磁性層の積層膜からなり、強磁性層間に電圧を印加しトンネル電流を流す。ＴＭＲ素子は、トンネル電流の大きさが上下の強磁性層の磁化の向きによって変化することを利用し、磁化の相対的角度の変化をトンネル抵抗値の変化として検出する。ＴＭＲ素子では、最大で５０％程度のＭＲ比が得られている。ＴＭＲ素子は、ＧＭＲ素子よりもＭＲ比が大きいため、信号電圧も大きくなる。しかし、純粋な信号成分だけでなく、ショットノイズによる雑音成分も大きくなり、Ｓ／Ｎ比（信号対雑音比）がよくならないという問題を抱えている。ショットノイズは、電子がトンネル障壁を不規則に通過することによって発生する電流の揺らぎに起因しており、トンネル抵抗の平方根に比例して増大する。従ってショットノイズを抑え、必要な信号電圧を得るには、トンネル絶縁層を薄くし、トンネル抵抗を低抵抗化する必要がある。記録密度が高密度化するほど素子サイズは記録ビットと同程度のサイズに小さくする必要があるため、高密度になるほどトンネル絶縁層の接合抵抗を小さく、つまり絶縁層を薄くする必要がある。３００Ｇｂｉｔ／ｉｎｃｈ2の記録密度では１Ω・ｃｍ2以下の接合抵抗が必要とされ、Ａｌ−Ｏ（アルミニウム酸化膜）トンネル絶縁層の膜厚に換算して原子２層分の厚さのトンネル絶縁層を形成しなければならない。トンネル絶縁層を薄くするほど上下電極間の短絡が生じやすくＭＲ比の低下を招くため、素子の作製は飛躍的に困難になっていく。以上の理由によってＴＭＲ素子を用いた場合の記録密度の限界は３００Ｇｂｉｔ／ｉｎｃｈ2程度であろうと見積もられている。 In order to cope with higher-density magnetic recording, development of a TMR element using the tunnel magnetoresistance effect (TMR effect) has been advanced. The TMR element is composed of a laminated film of a ferromagnetic layer / nonmagnetic insulating layer / ferromagnetic layer, and applies a voltage between the ferromagnetic layers to cause a tunnel current to flow. The TMR element utilizes the fact that the magnitude of the tunnel current changes depending on the magnetization directions of the upper and lower ferromagnetic layers, and detects a change in the relative angle of magnetization as a change in the tunnel resistance value. In the TMR element, a maximum MR ratio of about 50% is obtained. Since the TMR element has a larger MR ratio than the GMR element, the signal voltage is also increased. However, not only a pure signal component but also a noise component due to shot noise is increased, and the S / N ratio (signal-to-noise ratio) is not improved. Shot noise is caused by fluctuations in current generated by electrons passing irregularly through the tunnel barrier, and increases in proportion to the square root of the tunnel resistance. Therefore, in order to suppress shot noise and obtain a necessary signal voltage, it is necessary to make the tunnel insulating layer thin and to reduce the tunnel resistance. As the recording density increases, the element size needs to be reduced to the same size as the recording bit. Therefore, the higher the density, the lower the junction resistance of the tunnel insulating layer, that is, the thinner the insulating layer. With a recording density of 300 Gbit / inch 2 , a junction resistance of 1 Ω · cm 2 or less is required, and a tunnel insulating layer having a thickness of two atoms in terms of the thickness of an Al—O (aluminum oxide film) tunnel insulating layer. Must be formed. As the tunnel insulating layer is made thinner, a short circuit between the upper and lower electrodes is more likely to occur, and the MR ratio is lowered. For the above reasons, it is estimated that the limit of the recording density when the TMR element is used will be about 300 Gbit / inch 2 .

上に述べた素子はいずれも広い意味での磁気抵抗効果を利用しているが、これらの素子に共通した磁気的白色雑音（ホワイトノイズ）の問題が近年急浮上している（非特許文献１）。この雑音は上に述べたショットノイズなどの電気的ノイズとは異なり、微小磁化の熱ゆらぎに起因して生じるため素子の微細化に伴いより支配的となり、２００〜３００Ｇｂｐｓｉ対応の素子では電気的雑音よりも顕著になると考えられている。磁気的白色雑音を回避し、磁気記録の記録密度をさらに高めるためには従来の素子とは異なった原理により動作する微小磁気センサーの開発が必要となっている。
Appl. Phys. Lett., Vol. 78, No. 10 (2001) pp. 1448-1450. All of the above-described elements utilize the magnetoresistive effect in a broad sense, but the problem of magnetic white noise (white noise) common to these elements has recently emerged rapidly (Non-patent Document 1). ). Unlike the above-described electrical noise such as shot noise, this noise is caused by thermal fluctuation of minute magnetization, and therefore becomes more dominant as the element is miniaturized. In an element compatible with 200 to 300 Gbpsi, the electrical noise Is considered to be more prominent. In order to avoid magnetic white noise and further increase the recording density of magnetic recording, it is necessary to develop a micro magnetic sensor that operates on a principle different from that of a conventional element.
Appl. Phys. Lett., Vol. 78, No. 10 (2001) pp. 1448-1450.

本発明の目的は、磁気的白色雑音を低減して高密度磁気記録を実現できる磁気センサーを提供することにある。   An object of the present invention is to provide a magnetic sensor capable of reducing magnetic white noise and realizing high-density magnetic recording.

本発明の一態様に係る磁気センサーは、磁化固定層と、非磁性中間層と、磁化フリー層とを含む磁気抵抗効果素子と、前記磁気抵抗効果素子の磁化フリー層に磁気共鳴を誘起するマイクロ波発振素子と、前記磁気抵抗効果素子のマイクロ波出力を検波するダイオードとを具備することを特徴とする。 A magnetic sensor according to an aspect of the present invention includes a magnetoresistive element including a magnetization fixed layer, a nonmagnetic intermediate layer, and a magnetization free layer, and a microinducing magnetic resonance in the magnetization free layer of the magnetoresistive element. And a diode for detecting the microwave output of the magnetoresistive element.

本発明によれば、磁気的白色雑音を低減して高密度磁気記録を実現できる磁気センサーを提供できる。   ADVANTAGE OF THE INVENTION According to this invention, the magnetic sensor which can reduce a magnetic white noise and can implement | achieve a high-density magnetic recording can be provided.

以下、本発明を実施形態について説明する。   Hereinafter, embodiments of the present invention will be described.

最初に、図１、図２および図３を参照して、本発明の実施形態に係る磁気センサーの基本的な構成について説明する。   First, a basic configuration of a magnetic sensor according to an embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG.

図１の磁気センサーは、マイクロ波発振素子としての高周波電流源１と、磁気抵抗効果素子２０とを並列接続し、磁気抵抗効果素子２０の出力端にマイクロ波検波器３０を接続したものである。   The magnetic sensor of FIG. 1 has a high-frequency current source 1 as a microwave oscillation element 1 and a magnetoresistive effect element 20 connected in parallel, and a microwave detector 30 connected to the output end of the magnetoresistive effect element 20. .

図２の磁気センサーは、マイクロ波発振素子としての高周波電圧源２および抵抗３を含む直列回路と、磁気抵抗効果素子２０とを並列接続し、磁気抵抗効果素子２０の出力端にマイクロ波検波器３０を接続したものである。   The magnetic sensor shown in FIG. 2 has a series circuit including a high-frequency voltage source 2 as a microwave oscillation element 2 and a resistor 3 and a magnetoresistive element 20 connected in parallel, and a microwave detector is connected to the output terminal of the magnetoresistive element 20. 30 is connected.

図３の磁気センサーは、マイクロ波発振素子としての高周波電圧源２および磁気抵抗効果素子２０を含む直列回路と、抵抗３とを並列接続し、磁気抵抗効果素子２０の出力端にマイクロ波検波器３０を接続したものである。   The magnetic sensor of FIG. 3 has a series circuit including a high-frequency voltage source 2 and a magnetoresistive effect element 20 as a microwave oscillating element and a resistor 3 connected in parallel, and a microwave detector is connected to the output end of the magnetoresistive effect element 20. 30 is connected.

いずれの磁気センサーでも、マイクロ波発振素子により磁気抵抗効果素子２０の磁化フリー層に磁気共鳴を誘起し、外部磁場の印加による磁気共鳴の共鳴スペクトルの周波数変化または振幅変化に基づいて外部磁場を検出する。   In any of the magnetic sensors, magnetic resonance is induced in the magnetization free layer of the magnetoresistive effect element 20 by the microwave oscillating element, and the external magnetic field is detected based on the change in frequency or amplitude of the resonance spectrum of the magnetic resonance due to application of the external magnetic field To do.

本発明の実施形態に係る磁気センサーにおいて、磁場感知素子として磁気抵抗効果素子２０は、磁化固定層と、非磁性中間層と、磁化フリー層とを含む。磁気抵抗効果素子２０は、非磁性中間層が非磁性金属層であるＣＰＰ−ＭＲ素子でもよいし、非磁性中間層が非磁性絶縁層であるＴＭＲ素子でもよい。   In the magnetic sensor according to the embodiment of the present invention, the magnetoresistive effect element 20 as a magnetic field sensing element includes a magnetization fixed layer, a nonmagnetic intermediate layer, and a magnetization free layer. The magnetoresistive element 20 may be a CPP-MR element in which the nonmagnetic intermediate layer is a nonmagnetic metal layer, or a TMR element in which the nonmagnetic intermediate layer is a nonmagnetic insulating layer.

本発明の実施形態に係る磁気センサーにおいて、マイクロ波発振素子としては、半導体発振素子、磁気抵抗効果素子、磁性発振素子などが用いられる。マイクロ波発振素子として磁気抵抗効果素子を用いる場合、この磁気抵抗効果素子は発振しやすいように設計され、磁場感知素子としての磁気抵抗効果素子２０は磁場を検知しやすいように設計される。磁性発振素子とは、スピントンスファートルクによって磁性体の磁化に歳差運動を誘起する素子である。   In the magnetic sensor according to the embodiment of the present invention, a semiconductor oscillation element, a magnetoresistance effect element, a magnetic oscillation element, or the like is used as the microwave oscillation element. When a magnetoresistive effect element is used as the microwave oscillating element, the magnetoresistive effect element is designed to easily oscillate, and the magnetoresistive effect element 20 as the magnetic field sensing element is designed to easily detect the magnetic field. A magnetic oscillation element is an element that induces precession in the magnetization of a magnetic material by spinton spher torque.

本発明の実施形態に係る磁気センサーにおいて、マイクロ波検波器３０としては、ショットキーダイオードなどが用いられる。   In the magnetic sensor according to the embodiment of the present invention, a Schottky diode or the like is used as the microwave detector 30.

図４に、マイクロ波発振素子として磁気抵抗効果素子を用いた、本発明の実施形態に係る磁気センサーの構成図を示す。図４の磁気センサーは、マイクロ波発振素子としての第１の磁気抵抗効果素子（ＣＰＰ−ＭＲ素子）１０およびキャパシタ４を含む直列回路と、磁場感知素子としての第２の磁気抵抗効果素子（ＣＰＰ−ＭＲ素子）２０とを並列接続し、第２のＣＰＰ−ＭＲ素子２０の出力端にマイクロ波検波器３０を接続したものである。マイクロ波発振素子としての第１のＣＰＰ−ＭＲ素子１０は、磁化フリー層１１、非磁性金属層１２、磁化固定層１３を積層した構造を有する。磁場感知素子としての第２のＣＰＰ−ＭＲ素子２０は、磁化フリー層２１、非磁性金属層２２、磁化固定層２３を積層した構造を有する。   FIG. 4 shows a configuration diagram of a magnetic sensor according to an embodiment of the present invention using a magnetoresistive effect element as a microwave oscillation element. The magnetic sensor of FIG. 4 includes a series circuit including a first magnetoresistive element (CPP-MR element) 10 as a microwave oscillating element and a capacitor 4, and a second magnetoresistive element (CPP) as a magnetic field sensing element. -MR element) 20 is connected in parallel, and a microwave detector 30 is connected to the output terminal of the second CPP-MR element 20. The first CPP-MR element 10 as a microwave oscillation element has a structure in which a magnetization free layer 11, a nonmagnetic metal layer 12, and a magnetization fixed layer 13 are stacked. The second CPP-MR element 20 as a magnetic field sensing element has a structure in which a magnetization free layer 21, a nonmagnetic metal layer 22, and a magnetization fixed layer 23 are stacked.

以下、図４に示した磁気センサーの動作原理を説明する。第１のＣＰＰ−ＭＲ素子１０に電流Ｉを流すと素子の両端にフリー層磁化の熱ゆらぎに起因する雑音電圧が発生する。その実効値Ｖmagは（１）式のように表すことができる。

Figure 0004921897
Hereinafter, the operation principle of the magnetic sensor shown in FIG. 4 will be described. When a current I is passed through the first CPP-MR element 10, noise voltage due to thermal fluctuation of free layer magnetization is generated at both ends of the element. Its effective value V mag can be expressed as in equation (1).
Figure 0004921897

ここでＲは素子抵抗、ΔＲ／Ｒは磁気抵抗効果比（ＭＲ比）であり、Ｓ<mt>はフリー層磁化の熱ゆらぎのパワースペクトルである。Ｓ<mt>はフリー層の帯磁率の虚部χ"を用いて（２）式のように表される。

Figure 0004921897
Here, R is element resistance, ΔR / R is magnetoresistance effect ratio (MR ratio), and S <mt> is a power spectrum of thermal fluctuation of free layer magnetization. S <mt> is expressed as in equation (2) using the imaginary part χ ″ of the magnetic susceptibility of the free layer.
Figure 0004921897

ただしｋはボルツマン定数、Ｔは温度、ｆresは（３）式で示されるフリー層磁化の共鳴周波数、ＭsおよびＶはフリー層の飽和磁化および体積である。

Figure 0004921897
Where k is the Boltzmann constant, T is the temperature, f res is the resonance frequency of the free layer magnetization expressed by equation (3), and M s and V are the saturation magnetization and volume of the free layer.
Figure 0004921897

（３）式のＨは外部磁場、Ｈbはフリー層の異方性磁場ＨKやフリー層に印加された交換磁場ＨEなどを含めたバイアス磁場である。 (3) expression of H the external magnetic field, H b is the bias field, including such exchange field H E applied to the anisotropy field H K and the free layer of the free layer.

図５（ａ）に、（１）式の雑音電圧の周波数スペクトルを模式的に示す。雑音スペクトルは共鳴周波数ｆresにおいてピークを呈し、ピークの幅Δｆはギルバートの減衰係数αを用いてΔｆ＝２αｆresと表される。本発明の実施形態に係る磁気センサーを読み出し用磁気ヘッドとして用いる場合には、上記のスペクトル線幅が読み出し周波数（例えば３００ＭＨｚ）に比べて十分狭いことが好ましい。そのためには、フリー層磁化の減衰係数αが十分小さいことが好ましい。近年、磁性体へのスピン注入効果を利用することによりαを０．００１〜０．０００１程度に低減することが可能となっている。この効果を利用すると、ｆ＝５ＧＨｚの場合２αｆres＝０．０１〜０．００１ＧＨｚとなるので、スペクトル線幅を読み出し周波数の１／３０〜１／３００程度にすることが可能となる。すなわち、雑音電圧の振幅の時間変化である図５（ｂ）に示すように、読み出し時間（〜３ｎｓ）の間、発振電圧の振幅変動を１／３０以下に抑制することができる。 FIG. 5A schematically shows the frequency spectrum of the noise voltage of equation (1). The noise spectrum exhibits a peak at the resonance frequency f res , and the peak width Δf is expressed as Δf = 2αf res using Gilbert's attenuation coefficient α. When the magnetic sensor according to the embodiment of the present invention is used as a read magnetic head, it is preferable that the spectral line width is sufficiently narrower than a read frequency (for example, 300 MHz). For this purpose, it is preferable that the attenuation coefficient α of the free layer magnetization is sufficiently small. In recent years, α can be reduced to about 0.001 to 0.0001 by utilizing the spin injection effect on the magnetic material. If this effect is used, since 2αf res = 0.01 to 0.001 GHz when f = 5 GHz, the spectral line width can be reduced to about 1/30 to 1/300 of the readout frequency. That is, as shown in FIG. 5B, which is a time change in the amplitude of the noise voltage, the amplitude fluctuation of the oscillation voltage can be suppressed to 1/30 or less during the readout time (˜3 ns).

（２）式から明らかなように、磁化ゆらぎは飽和磁化Ｍsに逆比例するので、大きな出力電圧（電力）を得るためにはＭsの小さいフリー層を用いることが好ましい。Ｍsを小さくするには、フリー層として積層フェリ磁性体を用いることが有効であり、交換磁場を印加した積層フェリ磁性体を用いることも有効である。 As apparent from the equation (2), since the magnetization fluctuation is inversely proportional to the saturation magnetization M s , it is preferable to use a free layer having a small M s in order to obtain a large output voltage (power). In order to reduce M s , it is effective to use a laminated ferrimagnetic material as a free layer, and it is also effective to use a laminated ferrimagnetic material to which an exchange magnetic field is applied.

図６（ａ）に積層フェリ磁性体を示す。この積層フェリ磁性体は、第１の強磁性層５１、非磁性金属層（たとえばＲｕ）５２、および第２の強磁性層５３の積層体からなる。第１の強磁性層５１と第２の強磁性層５３とでは、磁化の大きさが異なる。この積層フェリ磁性体では、実効的なＭsを通常の磁性体の１／１００程度にまで低減させることができ、極めて大きな磁化の熱ゆらぎを生じさせることができる。 FIG. 6A shows a laminated ferrimagnetic material. This laminated ferrimagnetic material is composed of a laminated body of a first ferromagnetic layer 51, a nonmagnetic metal layer (for example, Ru) 52, and a second ferromagnetic layer 53. The first ferromagnetic layer 51 and the second ferromagnetic layer 53 have different magnetization magnitudes. In this laminated ferrimagnetic material, the effective M s can be reduced to about 1/100 of that of a normal magnetic material, and extremely large thermal fluctuation of magnetization can be generated.

しかし、（３）式からわかるように、Ｍsを低減すると共鳴周波数が低下する。共鳴周波数の低下を防ぐには、強い交換磁場ＨEを利用することが有効である。 However, as can be seen from the equation (3), when M s is reduced, the resonance frequency is lowered. To prevent degradation of the resonance frequency, it is effective to use a strong exchange field H E.

図６（ｂ）に交換磁場を印加した積層フェリ磁性体を示す。この積層フェリ磁性体は、図６（ａ）に示した積層フェリ磁性体の第１の強磁性層５１に、非磁性金属層（たとえばＲｕ）５４を介して反強磁性層５５を積層したものである。この積層フェリ磁性体では、反強磁性層５５を設けたことにより強い交換磁場を容易に印加することができる。なお、第１の強磁性層５１に、直接、反強磁性層５５を積層してもよい。   FIG. 6B shows a laminated ferrimagnetic material to which an exchange magnetic field is applied. In this laminated ferrimagnetic material, an antiferromagnetic layer 55 is laminated on a first ferromagnetic layer 51 of the laminated ferrimagnetic material shown in FIG. 6A via a nonmagnetic metal layer (for example, Ru) 54. It is. In this laminated ferrimagnetic material, a strong exchange magnetic field can be easily applied by providing the antiferromagnetic layer 55. Note that the antiferromagnetic layer 55 may be laminated directly on the first ferromagnetic layer 51.

膜厚ｔ、飽和磁化Ｍsのフリー層に印加される交換磁場ＨEは界面エネルギーΔＥを用いて（４）式のように表される。

Figure 0004921897
The exchange magnetic field H E applied to the free layer having the film thickness t and the saturation magnetization M s is expressed by the equation (4) using the interface energy ΔE.
Figure 0004921897

ΔＥは通常０．０１ｅｒｇ／ｃｍ2以下であるが、Ｍsが小さいため、数ｎｍのフリー層に数百〜数千Ｏｅの交換磁場を容易に印加することが可能である。交換磁場を利用すると、ハード層によるバイアス磁場を用いずに磁区制御や発振周波数の制御を行うことができる。 ΔE is usually 0.01 erg / cm 2 or less, but since M s is small, it is possible to easily apply an exchange magnetic field of several hundred to several thousand Oe to a free layer of several nm. When the exchange magnetic field is used, the magnetic domain control and the oscillation frequency can be controlled without using the bias magnetic field by the hard layer.

図４において、第１のＣＰＰ−ＭＲ素子（マイクロ波発振素子）１０で発生したマイクロ波電力は、第２のＣＰＰ−ＭＲ素子（磁場感知素子）２０に注入され、第２のＣＰＰ−ＭＲ素子２０にマイクロ波電流が流れる。図７（ａ）に示すように、第２のＣＰＰ−ＭＲ素子２０は、磁化フリー層２１、非磁性金属層２２、磁化固定層２３を積層した構造を有する。したがって、磁化固定層２３でスピン偏極されたマイクロ波電流が磁化フリー層２１へ流れる。図７（ａ）では、磁化固定層２３と磁化フリー層２１の磁化は互いに直交するように配置されている。最近の研究によると、スピン偏極した高周波電流はフリー層磁化に実効高周波磁場として作用するので、フリー層磁化の共鳴周波数と実効高周波磁場の周波数がほぼ一致した場合にはフリー層磁化に磁気共鳴を励起し、フリー層磁化は歳差運動を起こす。   In FIG. 4, the microwave power generated by the first CPP-MR element (microwave oscillation element) 10 is injected into the second CPP-MR element (magnetic field sensing element) 20 and the second CPP-MR element. A microwave current flows through 20. As shown in FIG. 7A, the second CPP-MR element 20 has a structure in which a magnetization free layer 21, a nonmagnetic metal layer 22, and a magnetization fixed layer 23 are stacked. Therefore, the microwave current spin-polarized by the magnetization fixed layer 23 flows to the magnetization free layer 21. In FIG. 7A, the magnetizations of the magnetization fixed layer 23 and the magnetization free layer 21 are arranged so as to be orthogonal to each other. According to recent research, the spin-polarized high-frequency current acts as an effective high-frequency magnetic field on the free layer magnetization, so when the resonance frequency of the free layer magnetization and the frequency of the effective high-frequency magnetic field are almost the same, the magnetic resonance in the free layer magnetization The free layer magnetization causes precession.

実効高周波磁場ｈの大きさは高周波電流密度ｉに比例し、フリー層の厚さｔおよび飽和磁化Ｍsに反比例する。Ｍs＝１０００Ｇ、ｔ＝１ｎｍの場合、高周波電流密度ｉが１０6Ａ／ｃｍ2で｜ｈ｜は数十Ｏｅである。より小さな電流密度ｉで大きな高周波磁場を発生させるためにはフリー層として積層フェリ磁性体を用い磁化Ｍsを減少させることが有効である。 The magnitude of the effective high-frequency magnetic field h is proportional to the high-frequency current density i, and inversely proportional to the free layer thickness t and the saturation magnetization M s . When M s = 1000 G and t = 1 nm, the high-frequency current density i is 10 6 A / cm 2 and | h | is several tens of Oe. In order to generate a large high-frequency magnetic field with a smaller current density i, it is effective to reduce the magnetization M s by using a laminated ferrimagnetic material as a free layer.

図７（ｂ）に示すように、磁化フリー層２１の両面にそれぞれ非磁性金属層２２、２４を介して磁化固定層２３、２５を積層すると、ｈが増大することも知られている。   As shown in FIG. 7B, it is also known that when the magnetization fixed layers 23 and 25 are laminated on both surfaces of the magnetization free layer 21 via the nonmagnetic metal layers 22 and 24, respectively, h increases.

図８の挿入図に示した磁化の歳差運動の角度（歳差角）が数十度に達する大振幅の磁気共鳴を生じさせるために必要な高周波磁場の大きさは数十Ｏｅと見積もられる。したがって、上記フリー層を用いた場合、１０6Ａ／ｃｍ2程度の高周波電流で大振幅の磁気共鳴を励起することができる。 The magnitude of the high-frequency magnetic field required to generate a large-amplitude magnetic resonance in which the magnetization precession angle (precession angle) shown in the inset of FIG. 8 reaches several tens of degrees is estimated to be several tens of Oe. . Therefore, when the free layer is used, large-amplitude magnetic resonance can be excited with a high-frequency current of about 10 6 A / cm 2 .

図８に、周波数と歳差角との関係を示す。図８に示したように、磁化フリー層のバイアス磁場方向に印加される外部磁場が（＋）または（−）に変化すると、磁化フリー層の共鳴周波数が変化する。また、発振周波数における歳差角も変化する。ここで、（＋）と（−）とは、たとえば磁気記録媒体に記録されたアップスピンまたはダウンスピンに相当する。   FIG. 8 shows the relationship between the frequency and the precession angle. As shown in FIG. 8, when the external magnetic field applied in the bias magnetic field direction of the magnetization free layer changes to (+) or (−), the resonance frequency of the magnetization free layer changes. In addition, the precession angle at the oscillation frequency also changes. Here, (+) and (−) correspond to, for example, upspin or downspin recorded on a magnetic recording medium.

本発明の実施形態に係る磁気センサーを磁気ヘッドとして用いる場合、歳差角が読み出し周波数（例えば３００ＭＨｚ）に追随して容易に変化することが好ましい。歳差角が追随できる周波数の上限は共鳴スペクトル幅程度なので、第２のＣＰＰ−ＭＲ素子２０の磁化フリー層２１には図８に示したように共鳴スペクトル幅の広い（約２ＧＨｚ）磁性体を用いることが好ましい。   When the magnetic sensor according to the embodiment of the present invention is used as a magnetic head, it is preferable that the precession angle easily changes following the read frequency (for example, 300 MHz). Since the upper limit of the frequency at which the precession angle can follow is about the resonance spectrum width, a magnetic material having a wide resonance spectrum width (about 2 GHz) is used for the magnetization free layer 21 of the second CPP-MR element 20 as shown in FIG. It is preferable to use it.

第２のＣＰＰ−ＭＲ素子２０の両端に発生する高周波電圧の振幅は、歳差運動の角度（の余弦）とＭＲ比の積に比例して変化する。したがって、図９（ａ）および（ｂ）に示すように、高周波電圧（図９ａ図示）の振幅は、外部磁場（図９ｂ図示）の変化に伴って、図示したように変化する。そして、第２のＣＰＰ−ＭＲ素子２０から出力される高周波電圧を、ショットキーダイオードなどのマイクロ波検波器３０で検波することにより、磁場変化ΔＨを電圧変化ΔＶとして取出すことができる。   The amplitude of the high-frequency voltage generated at both ends of the second CPP-MR element 20 changes in proportion to the product of the precession angle (cosine thereof) and the MR ratio. Accordingly, as shown in FIGS. 9A and 9B, the amplitude of the high-frequency voltage (shown in FIG. 9A) changes as shown in accordance with the change in the external magnetic field (shown in FIG. 9B). The magnetic field change ΔH can be taken out as the voltage change ΔV by detecting the high-frequency voltage output from the second CPP-MR element 20 by the microwave detector 30 such as a Schottky diode.

第１のＣＰＰ−ＭＲ素子（マイクロ波発振素子）の発振周波数と、第２のＣＰＰ−ＭＲ素子（磁場感知素子）２０の共鳴周波数を適切に制御すると、（＋）または（−）の一方向の磁場極性に限られるものの、磁場感度を著しく高めることができる。図１０に、外部磁場が（−）の場合に、歳差角が著しく高まる例を示す。図１０とは逆に、外部磁場が（＋）である場合に、歳差角が著しく高まるように制御することもできる。したがって、（＋）極性および（−）極性をもつ１組のセンサーを組み合わせることにより、非常に感度の高い磁気ヘッドを構成することができる。   When the oscillation frequency of the first CPP-MR element (microwave oscillation element) and the resonance frequency of the second CPP-MR element (magnetic field sensing element) 20 are appropriately controlled, one direction of (+) or (-) However, the sensitivity of the magnetic field can be remarkably enhanced. FIG. 10 shows an example in which the precession angle is remarkably increased when the external magnetic field is (−). Contrary to FIG. 10, when the external magnetic field is (+), the precession angle can be controlled to be significantly increased. Therefore, a very sensitive magnetic head can be configured by combining a pair of sensors having (+) polarity and (−) polarity.

本発明の他の実施形態に係る磁気センサーにおいては、それぞれマイクロ波発振素子および磁場感知素子として機能する磁気抵抗効果素子として、ＣＰＰ−ＭＲ素子の代わりにＴＭＲ素子を用いることもできる。図１１（ａ）および（ｂ）にＴＭＲ素子を示す。図１１（ａ）のＴＭＲ素子は、磁化フリー層２１、絶縁層２６、磁化固定層２３を積層した構造を有する。図１１（ｂ）のＴＭＲ素子は、図１１（ａ）のＴＭＲ素子に磁化フリー層２１に非磁性金属層２４を介して磁化固定層２５を積層した構造を有する。   In a magnetic sensor according to another embodiment of the present invention, a TMR element can be used instead of a CPP-MR element as a magnetoresistive effect element that functions as a microwave oscillation element and a magnetic field sensing element, respectively. FIGS. 11A and 11B show TMR elements. The TMR element of FIG. 11A has a structure in which a magnetization free layer 21, an insulating layer 26, and a magnetization fixed layer 23 are stacked. The TMR element of FIG. 11B has a structure in which a magnetization fixed layer 25 is stacked on a magnetization free layer 21 via a nonmagnetic metal layer 24 on the TMR element of FIG.

また、出力電圧ΔＶ（または電力）を増大させるために、複数の素子を積層することも有効である。   It is also effective to stack a plurality of elements in order to increase the output voltage ΔV (or power).

本発明の他の実施形態に係る磁気センサーにおいては、磁場感知素子として機能する磁気抵抗効果素子に、図１２（ａ）および（ｂ）に示したように、磁化フリー層２１の磁化と磁化固定層２３（および２５）の磁化とが互いに平行なＣＰＰ−ＭＲ素子（またはＴＭＲ素子）を用いてもよい。平行磁化の磁気センサーは、直交磁化の磁気センサーに比較して感度は劣るものの、図１３（ａ）および（ｂ）に示したように、外部磁場（図１３ｂ）の変化に対して、出力として一方の極性の高周波電圧波形が得られるため、マイクロ波検波器が不要になる。   In the magnetic sensor according to another embodiment of the present invention, as shown in FIGS. 12A and 12B, the magnetization and magnetization of the magnetization free layer 21 are fixed to the magnetoresistive effect element that functions as a magnetic field sensing element. A CPP-MR element (or TMR element) in which the magnetization of the layer 23 (and 25) is parallel to each other may be used. Although the parallel magnetization magnetic sensor is inferior in sensitivity to the orthogonal magnetization magnetic sensor, as shown in FIGS. 13 (a) and 13 (b), as an output in response to a change in the external magnetic field (FIG. 13b). Since a high-frequency voltage waveform having one polarity is obtained, a microwave detector is not necessary.

本発明の実施形態に係る磁気センサーの最も大きな特徴は、磁場感知素子としての磁気抵抗効果素子のフリー層磁化の熱ゆらぎに伴う磁気的熱雑音が、通常のＧＭＲセンサーに比較して小さいことである。以下、その理由を説明する。   The most significant feature of the magnetic sensor according to the embodiment of the present invention is that the magnetic thermal noise accompanying the thermal fluctuation of the free layer magnetization of the magnetoresistive effect element as the magnetic field sensing element is smaller than that of a normal GMR sensor. is there. The reason will be described below.

磁化の熱ゆらぎは磁性体の格子振動に起因する熱振動磁場ｈTによって発生する。熱振動磁場ｈTの大きさは、磁性体の体積、飽和磁化の大きさ、観測する周波数帯域幅などに依存する。例えば、１００ｎｍ×１００ｎｍ×１ｎｍの体積を持つＦｅ、Ｃｏなどの代表的な磁性体では、１ＧＨｚの帯域幅で、熱振動磁場ｈTの大きさは１Ｏｅ程度である。この熱振動磁場と高周波帯磁率の積が磁化の熱ゆらぎを与える。 The thermal fluctuation of magnetization is generated by the thermal vibration magnetic field h T caused by the lattice vibration of the magnetic material. The magnitude of the thermal oscillating magnetic field h T depends on the volume of the magnetic material, the magnitude of the saturation magnetization, the frequency bandwidth to be observed, and the like. For example, in a typical magnetic material such as Fe or Co having a volume of 100 nm × 100 nm × 1 nm, the thermal oscillation magnetic field h T is about 1 Oe with a bandwidth of 1 GHz. The product of the thermal oscillating magnetic field and the high frequency magnetic susceptibility gives the thermal fluctuation of magnetization.

ＧＭＲ素子を用いた通常の磁気センサーでは、フリー層磁化はほぼ熱平衡状態にあるため、熱振動磁場ｈTと熱平衡状態の高周波帯磁率χTの積が磁化の熱ゆらぎとなる。一方、本発明の実施形態に係る磁気センサーでは、上述したようにフリー層は数十Ｏｅの大きな高周波磁場ｈの下で磁気共鳴状態にあり、フリー層磁化は熱平衡状態から大きくずれている。この非平衡状態に、小さな熱振動磁場ｈTが作用する。 In a normal magnetic sensor using a GMR element, the free layer magnetization is almost in a thermal equilibrium state. Therefore, the product of the thermal oscillation magnetic field h T and the high-frequency magnetic susceptibility χ T in the thermal equilibrium state becomes the thermal fluctuation of the magnetization. On the other hand, in the magnetic sensor according to the embodiment of the present invention, as described above, the free layer is in a magnetic resonance state under a high-frequency magnetic field h of several tens of Oe, and the free layer magnetization is greatly deviated from the thermal equilibrium state. A small thermal oscillation magnetic field h T acts on this non-equilibrium state.

図１４に、高周波磁場ｈの振幅と、高周波磁場ｈにより誘起される磁化の横成分の割合（飽和磁化との比）との関係を示す。図１４の縦軸は、歳差角の正弦に対応する。図１４からわかるように、高周波帯磁率は一般に強い非線形性を示し、高周波磁場の増大に伴って減少する。図１４において、大きな高周波磁場が印加された領域ＩＩにおける微分帯磁率は、熱平衡状態の領域Ｉにおける帯磁率の１／１０以下であり、熱振動磁場ｈTにより誘起される磁化の熱ゆらぎも１／１０以下となる。すなわち、本発明の磁気センサーではフリー層磁化の熱ゆらぎに伴う磁気的熱雑音が通常のＧＭＲセンサーに比較して大幅に低下する。 FIG. 14 shows the relationship between the amplitude of the high-frequency magnetic field h and the ratio of the transverse component of magnetization induced by the high-frequency magnetic field h (ratio to the saturation magnetization). The vertical axis in FIG. 14 corresponds to the sine of the precession angle. As can be seen from FIG. 14, the high-frequency magnetic susceptibility generally shows a strong non-linearity and decreases as the high-frequency magnetic field increases. In FIG. 14, the differential magnetic susceptibility in region II to which a large high-frequency magnetic field is applied is 1/10 or less of the magnetic susceptibility in region I in the thermal equilibrium state, and the thermal fluctuation of magnetization induced by thermal vibration magnetic field h T is also 1 / 10 or less. That is, in the magnetic sensor of the present invention, the magnetic thermal noise accompanying the thermal fluctuation of the free layer magnetization is greatly reduced as compared with a normal GMR sensor.

（１）マイクロ波発振素子としてのＴＭＲ素子（磁性発振素子）の作製
スパッタリングによる成膜と電子線リソグラフィーにより、図１５（ａ）に示すＴＭＲ素子を作製した。このＴＭＲ素子は、サファイア基板１０１上に、１００ｎｍのＣｕからなる下部電極１０２、２０ｎｍのＩｒＭｎからなる反強磁性層１０３、３ｎｍの積層フェリ磁性体（図１５ｂ）からなる磁化フリー層１０４、１ｎｍのＡｌＯxからなる誘電体層１０５、５０ｎｍのＣｏからなる磁化固定層１０６、２０ｎｍのＩｒＭｎからなる反強磁性層１０７、１００ｎｍのＣｕからなる上部電極１０８を積層した構造を有する。図１５（ｂ）に示すように、磁化フリー層１０４の積層フェリ磁性体は、Ｒｕ（０．３ｎｍ）１１１／Ｃｏ（０．７ｎｍ）１１２／Ｒｕ（０．８ｎｍ）１１３／Ｃｏ（１ｎｍ）１１４の積層体である。最下層のＲｕ（０．３ｎｍ）１１１は、ＩｒＭｎからなる反強磁性層１０３から磁化フリー層（積層フェリ磁性体）１０４に弱い交換相互作用を及ぼすために挿入している。磁性層の形成は約１０００Ｏｅの磁場印加の下で行い、磁化フリー層１０４の磁化と磁化固定層１０６の磁化が互いに直交するように一軸磁気異方性と交換バイアスが付与されている。接合面積は３００×１００ｎｍ2とした。素子抵抗は５４Ωであった。 (1) Production of TMR element (magnetic oscillation element) as microwave oscillation element The TMR element shown in FIG. 15A was produced by film formation by sputtering and electron beam lithography. This TMR element comprises a sapphire substrate 101, a lower electrode 102 made of 100 nm Cu, an antiferromagnetic layer 103 made of 20 nm IrMn, a magnetic free layer 104 made of a laminated ferrimagnetic material of 3 nm (FIG. 15b), and a 1 nm It has a structure in which a dielectric layer 105 made of AlO x, a magnetization pinned layer 106 made of 50 nm Co, an antiferromagnetic layer 107 made of IrMn 20 nm, and an upper electrode 108 made of 100 nm Cu are laminated. As shown in FIG. 15B, the laminated ferrimagnetic material of the magnetization free layer 104 is Ru (0.3 nm) 111 / Co (0.7 nm) 112 / Ru (0.8 nm) 113 / Co (1 nm) 114. It is a laminated body. The lowermost Ru (0.3 nm) 111 is inserted in order to exert a weak exchange interaction from the antiferromagnetic layer 103 made of IrMn to the magnetization free layer (laminated ferrimagnetic material) 104. The magnetic layer is formed under application of a magnetic field of about 1000 Oe, and uniaxial magnetic anisotropy and exchange bias are applied so that the magnetization of the magnetization free layer 104 and the magnetization of the magnetization fixed layer 106 are orthogonal to each other. The junction area was 300 × 100 nm 2 . The element resistance was 54Ω.

このＴＭＲ素子に１０ｍＡの直流電流を流した状態でスペクトルアナライザーを用いて雑音スペクトルの測定を行った。図１６に、スペクトル線幅にほぼ等しい８ＭＨｚのバンド幅で観測した電圧スペクトルを示す。周波数４．７ＧＨｚに実効値６５ｍＶの鋭い電圧ピークが観測され、このＴＭＲ素子がマイクロ波発振素子として機能することが確認された。測定結果から、素子のＭＲ比は約３０％、磁化フリー層の減衰係数αは約０．００１、バイアス磁場は約１５００Ｏｅであることが推定された。   A noise spectrum was measured using a spectrum analyzer in a state where a DC current of 10 mA was passed through the TMR element. FIG. 16 shows a voltage spectrum observed with a bandwidth of 8 MHz substantially equal to the spectral line width. A sharp voltage peak with an effective value of 65 mV was observed at a frequency of 4.7 GHz, and it was confirmed that this TMR element functions as a microwave oscillation element. From the measurement results, it was estimated that the MR ratio of the element was about 30%, the attenuation coefficient α of the magnetization free layer was about 0.001, and the bias magnetic field was about 1500 Oe.

（２）磁場感知素子としてのＴＭＲ素子の作製
実施例１と同様の方法で図１７に示すＴＭＲ素子を作製した。このＴＭＲ素子は、サファイア基板２０１上に、１００ｎｍのＣｕからなる下部電極２０２、５０ｎｍのＩｒＭｎからなる反強磁性層２０３、５０ｎｍのＦｅＣｏからなる磁化固定層２０４、０．５ｎｍのＡｌＯxからなる誘電体層２０５、２ｎｍのＦｅＣｏからなる磁化フリー層２０６、５０ｎｍのＡｕからなるキャップ層２０７、１００ｎｍのＣｕからなる上部電極２０８を積層した構造を有する。このＴＭＲ素子でも、磁化フリー層２０６と磁化固定層２０４の磁化容易軸は直交している。接合面積は１００×５０ｎｍ2とした。素子抵抗は４５Ωであった。 (2) Production of TMR Element as Magnetic Field Sensing Element A TMR element shown in FIG. 17 was produced in the same manner as in Example 1. This TMR element has a sapphire substrate 201, a lower electrode 202 made of 100 nm Cu, an antiferromagnetic layer 203 made of 50 nm IrMn, a magnetization fixed layer 204 made of 50 nm FeCo, and a dielectric made of 0.5 nm AlO x. The body layer 205 has a structure in which a magnetization free layer 206 made of 2 nm FeCo, a cap layer 207 made of 50 nm Au, and an upper electrode 208 made of 100 nm Cu are stacked. Also in this TMR element, the magnetization easy axes of the magnetization free layer 206 and the magnetization fixed layer 204 are orthogonal. The junction area was 100 × 50 nm 2 . The element resistance was 45Ω.

磁化フリー層２０６の容易軸方向に外部磁場を印加した状態で、素子に１ｍＡの電流を流し、磁気的熱雑音を測定することにより磁気共鳴の観測を行った。スペクトルアナライザーのバンド幅は実施例１と同様に８ＭＨｚとした。図１８に周波数と雑音電圧との関係を示す。曲線（ａ）は無磁場状態、曲線（ｂ）および（ｃ）はそれぞれ＋３０Ｏｅ、−３０Ｏｅの外部磁場を印加した状態で測定したものである。外部磁場により共鳴スペクトルが大きく変化することがわかる。図中の縦線は（１）で作製したマイクロ波発振素子の発振周波数を示している。特に、この周波数において共鳴強度が外部磁場により大きく変化することがわかる。共鳴曲線から求めた素子のＭＲ比は約３０％、磁化フリー層の減衰係数αは約０．０３、異方性磁場は約１５０Ｏｅであることが推定された。   With an external magnetic field applied in the easy axis direction of the magnetization free layer 206, a current of 1 mA was passed through the element, and magnetic thermal noise was measured to observe magnetic resonance. The bandwidth of the spectrum analyzer was set to 8 MHz as in Example 1. FIG. 18 shows the relationship between frequency and noise voltage. Curve (a) is measured with no magnetic field, and curves (b) and (c) are measured with an external magnetic field of +30 Oe and −30 Oe applied, respectively. It can be seen that the resonance spectrum changes greatly due to the external magnetic field. The vertical line in the figure indicates the oscillation frequency of the microwave oscillation device fabricated in (1). In particular, it can be seen that at this frequency, the resonance intensity varies greatly with the external magnetic field. It was estimated that the MR ratio of the element obtained from the resonance curve was about 30%, the attenuation coefficient α of the magnetization free layer was about 0.03, and the anisotropic magnetic field was about 150 Oe.

（３）信号磁場の測定
（１）で作製したマイクロ波発振素子としてのＴＭＲ素子、（２）で作製した磁場感知素子としてのＴＭＲ素子、およびマイクロ波検波器としてのショットキーダイオードを図４に示したように接続し、磁気センサーを構成した。なお、マイクロ波発振素子として用いたＴＭＲ素子は、外部磁場によって発振周波数が変化しないように、パーマロイ（登録商標）からなる磁気シールド内に収納した。出力電圧の増幅にはバンド幅１．５ＧＨｚの広帯域増幅器を用い、５０ＭＨｚ以下の周波数成分をフィルターでカットした。 (3) Measurement of signal magnetic field FIG. 4 shows a TMR element as a microwave oscillation element produced in (1), a TMR element as a magnetic field sensing element produced in (2), and a Schottky diode as a microwave detector. The magnetic sensor was configured by connecting as shown. The TMR element used as the microwave oscillation element was housed in a magnetic shield made of Permalloy (registered trademark) so that the oscillation frequency was not changed by an external magnetic field. A wideband amplifier with a bandwidth of 1.5 GHz was used for amplification of the output voltage, and frequency components of 50 MHz or less were cut with a filter.

この磁気センサーに、図１９（ａ）に示した信号磁場を印加し信号電圧を測定した。図１９（ｂ）に信号電圧の測定結果を示す。この図の縦軸には信号電圧の（増幅器への）入力換算値を示している。３０Ｏｅの信号磁場に対して、約２．５ｍＶの大きな信号電圧が観測される。また、増幅器雑音を除いた信号電圧のＳ／Ｎ比は約３０（３０ｄＢ）ときわめて大きいことが分かった。   The signal magnetic field shown in FIG. 19A was applied to this magnetic sensor, and the signal voltage was measured. FIG. 19B shows the measurement result of the signal voltage. The vertical axis of this figure shows the input converted value (to the amplifier) of the signal voltage. A large signal voltage of about 2.5 mV is observed for a signal magnetic field of 30 Oe. Further, it was found that the S / N ratio of the signal voltage excluding the amplifier noise was as extremely large as about 30 (30 dB).

以上説明したように、マイクロ波発振素子と、磁場感知素子としてのＣＰＰ−ＭＲやＴＭＲなどの磁気抵抗効果素子を組み合わせて、外部磁場による磁気抵抗効果素子の共鳴周波数の変化に基づいて高速応答が可能な高感度磁気センサーを形成することができる。本発明の実施形態に係る磁気センサーは、磁気的熱雑音が小さいため、高密度読み取り用磁気ヘッドなどへの応用が可能である。   As described above, combining a microwave oscillation element and a magnetoresistive effect element such as CPP-MR or TMR as a magnetic field sensing element, a high-speed response is achieved based on a change in the resonance frequency of the magnetoresistive effect element due to an external magnetic field. Possible high sensitivity magnetic sensors can be formed. Since the magnetic sensor according to the embodiment of the present invention has low magnetic thermal noise, it can be applied to a magnetic head for high-density reading.

なお、本発明は上述した実施形態に限定されない。例えば、マイクロ波発振素子として異なるタイプの磁性発振素子や、半導体発振素子を用いてもよい。また、磁場感知素子として用いられる磁気抵抗効果素子の磁化フリー層や磁化固定層に垂直磁化膜を用いてもよい。   In addition, this invention is not limited to embodiment mentioned above. For example, a different type of magnetic oscillation element or semiconductor oscillation element may be used as the microwave oscillation element. Further, a perpendicular magnetization film may be used for the magnetization free layer and the magnetization fixed layer of the magnetoresistive effect element used as the magnetic field sensing element.

本発明の実施形態に係る磁気センサーの基本的な構成図。1 is a basic configuration diagram of a magnetic sensor according to an embodiment of the present invention. 本発明の他の実施形態に係る磁気センサーの基本的な構成図。The basic block diagram of the magnetic sensor which concerns on other embodiment of this invention. 本発明のさらに他の実施形態に係る磁気センサーの基本的な構成図。The basic block diagram of the magnetic sensor which concerns on other embodiment of this invention. マイクロ波発振素子として磁気抵抗効果素子を用いた、本発明の実施形態に係る磁気センサーの構成図。The block diagram of the magnetic sensor which concerns on embodiment of this invention using the magnetoresistive effect element as a microwave oscillation element. 雑音電圧の周波数スペクトル、および雑音電圧の振幅の時間変化を示す図。The figure which shows the time change of the frequency spectrum of noise voltage, and the amplitude of noise voltage. 積層フェリ磁性体の断面図。Sectional drawing of a laminated ferrimagnetic material. 磁場感知素子としてのＣＰＰ−ＭＲ素子の断面図。Sectional drawing of the CPP-MR element as a magnetic field sensing element. 周波数と歳差角との関係の一例を示す図。The figure which shows an example of the relationship between a frequency and a precession angle. 高周波電圧の振幅と外部磁場との関係の一例を示す図。The figure which shows an example of the relationship between the amplitude of a high frequency voltage, and an external magnetic field. 周波数と歳差角との関係の他の例を示す図。The figure which shows the other example of the relationship between a frequency and a precession angle. 磁場感知素子としてのＴＭＲ素子の断面図。A sectional view of a TMR element as a magnetic field sensing element. 磁場感知素子としての平行磁場のＣＰＰ−ＭＲ素子の断面図。Sectional drawing of the CPP-MR element of a parallel magnetic field as a magnetic field sensing element. 高周波電圧の振幅と外部磁場との関係の他の例を示す図。The figure which shows the other example of the relationship between the amplitude of a high frequency voltage, and an external magnetic field. 高周波磁場ｈの振幅と、高周波磁場ｈにより誘起される磁化の横成分の割合（飽和磁化との比）との関係を示す図。The figure which shows the relationship between the amplitude of the high frequency magnetic field h, and the ratio (ratio with saturation magnetization) of the transverse component of the magnetization induced by the high frequency magnetic field h. 実施例におけるマイクロ波発振素子としてのＴＭＲ素子の断面図。Sectional drawing of the TMR element as a microwave oscillation element in an Example. 図１５のＴＭＲ素子の電圧スペクトルを示す図。The figure which shows the voltage spectrum of the TMR element of FIG. 実施例における磁場感知素子としてのＴＭＲ素子の断面図。Sectional drawing of the TMR element as a magnetic field sensing element in an Example. 図１７のＴＭＲ素子について周波数と雑音電圧との関係を示す図。The figure which shows the relationship between a frequency and a noise voltage about the TMR element of FIG. 実施例の磁気センサーについて、信号磁場と信号電圧とを示す図。The figure which shows a signal magnetic field and a signal voltage about the magnetic sensor of an Example.

符号の説明Explanation of symbols

１…高周波電流源、２…高周波電圧源、３…抵抗、４…キャパシタ、１０…磁気抵抗効果素子（マイクロ波発振素子）、１１…磁化フリー層、１２…非磁性金属層、１３…磁化固定層、２０…磁気抵抗効果素子（磁場感知素子）、２１…磁化フリー層、２２…非磁性金属層、２３…磁化固定層、２４…非磁性金属層、２５…磁化固定層、２６…絶縁層、３０…マイクロ波検波器、５１…第１の強磁性層、５２…非磁性金属層、５３…第２の強磁性層、１０１…サファイア基板、１０２…下部電極、１０３…反強磁性層、１０４…磁化フリー層、１０５…誘電体層、１０６…磁化固定層、１０７…反強磁性層、１０８…上部電極、１１１…Ｒｕ、１１２…Ｃｏ、１１３…Ｒｕ、１１４…Ｃｏ、２０１…サファイア基板、２０２…下部電極、２０３…反強磁性層、２０４…磁化固定層、２０５…誘電体層、２０６…磁化フリー層、２０７…キャップ層、２０８…上部電極。   DESCRIPTION OF SYMBOLS 1 ... High frequency current source, 2 ... High frequency voltage source, 3 ... Resistance, 4 ... Capacitor, 10 ... Magnetoresistive effect element (microwave oscillation element), 11 ... Magnetization free layer, 12 ... Nonmagnetic metal layer, 13 ... Magnetization fixed 20, magnetoresistive effect element (magnetic field sensing element), 21, magnetization free layer, 22, nonmagnetic metal layer, 23, magnetization fixed layer, 24, nonmagnetic metal layer, 25, magnetization fixed layer, 26, insulating layer , 30 ... Microwave detector, 51 ... First ferromagnetic layer, 52 ... Nonmagnetic metal layer, 53 ... Second ferromagnetic layer, 101 ... Sapphire substrate, 102 ... Lower electrode, 103 ... Antiferromagnetic layer, DESCRIPTION OF SYMBOLS 104 ... Magnetization free layer, 105 ... Dielectric layer, 106 ... Magnetization fixed layer, 107 ... Antiferromagnetic layer, 108 ... Upper electrode, 111 ... Ru, 112 ... Co, 113 ... Ru, 114 ... Co, 201 ... Sapphire substrate 202 ... Lower electrode, 20 ... antiferromagnetic layer, 204 ... fixed magnetization layer, 205 ... dielectric layer, 206 ... magnetization free layer, 207 ... cap layer, 208 ... upper electrode.

Claims (7)

磁化固定層と、非磁性中間層と、磁化フリー層とを含む磁気抵抗効果素子と、
前記磁気抵抗効果素子の磁化フリー層に磁気共鳴を誘起するマイクロ波発振素子と、
前記磁気抵抗効果素子のマイクロ波出力を検波するダイオードと
を具備することを特徴とする磁気センサー。 A magnetoresistive effect element including a magnetization fixed layer, a nonmagnetic intermediate layer, and a magnetization free layer;
A microwave oscillation element for inducing magnetic resonance in the magnetization free layer of the magnetoresistive element;
A magnetic sensor comprising a diode for detecting a microwave output of the magnetoresistive element. 前記マイクロ波発振素子により前記磁気抵抗効果素子の磁化フリー層に磁気共鳴が誘起され、外部磁場の印加による前記磁気共鳴の共鳴スペクトルの周波数変化または振幅変化に基づいて外部磁場が検出されることを特徴とする請求項１に記載の磁気センサー。   Magnetic resonance is induced in the magnetization free layer of the magnetoresistive effect element by the microwave oscillating element, and an external magnetic field is detected based on a change in frequency or amplitude of a resonance spectrum of the magnetic resonance due to application of an external magnetic field. The magnetic sensor according to claim 1. 前記磁気抵抗効果素子の磁化フリー層に、直接または非磁性層を介して、反強磁性層が積層されていることを特徴とする請求項１または請求項２に記載の磁気センサー。   3. The magnetic sensor according to claim 1, wherein an antiferromagnetic layer is laminated directly or via a nonmagnetic layer on the magnetization free layer of the magnetoresistive element. 前記マイクロ波発振素子は、半導体発振素子であることを特徴とする請求項１ないし３のいずれか１項に記載の磁気センサー。   The magnetic sensor according to claim 1, wherein the microwave oscillation element is a semiconductor oscillation element. 前記マイクロ波発振素子は、磁化固定層と、非磁性中間層と、磁化フリー層とを含む磁気抵抗効果素子であることを特徴とする請求項１ないし３のいずれか１項に記載の磁気センサー。   4. The magnetic sensor according to claim 1, wherein the microwave oscillating element is a magnetoresistive effect element including a magnetization fixed layer, a nonmagnetic intermediate layer, and a magnetization free layer. 5. . 前記マイクロ波発振素子としての磁気抵抗効果素子は、磁化フリー層および磁化固定層の少なくても一方が積層フェリ磁性体で形成されていることを特徴とする請求項５に記載の磁気センサー。   6. The magnetic sensor according to claim 5, wherein at least one of the magnetization free layer and the magnetization fixed layer of the magnetoresistive effect element as the microwave oscillation element is formed of a laminated ferrimagnetic material. 前記マイクロ波発振素子は、スピントンスファートルクによって磁性体の磁化に歳差運動を誘起する素子であることを特徴とする請求項１ないし３のいずれか１項に記載の磁気センサー。   4. The magnetic sensor according to claim 1, wherein the microwave oscillating element is an element that induces precession in the magnetization of a magnetic material by spinton spher torque. 5.
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