JP5032009B2 - Magnetic sensor, magnetic head, and magnetic recording / reproducing apparatus - Google Patents

Description

  The present invention relates to a magnetic sensor, a magnetic head, and a magnetic recording / reproducing apparatus.

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 layer / ferromagnetic layer. The GMR element applies an exchange bias to one of the ferromagnetic layers 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 (Current In Plane) -GMR element that detects a resistance change by passing a current through the film surface of the spin valve film, and a CPP (Current Perpendicular to Plane) that detects a resistance change by flowing a current perpendicular to the film surface of the spin valve film ) -GMR elements 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.

  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 / insulator / ferromagnetic layer, and applies a voltage between the ferromagnetic layers to cause a tunnel current to flow. The TMR element is an element that detects a change in the relative angle of magnetization as a change in tunnel resistance value by utilizing the fact that the magnitude of the tunnel current changes depending on the magnetization directions of the upper and lower ferromagnetic layers. An element having an MR ratio of about 50% at maximum 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 value. 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 smaller 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 the tunnel insulating layer has a thickness of two atoms in terms of the thickness of the 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 TMR element will be 300 Gbit / inch ² .

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. Unlike electrical noise such as shot noise described above, this noise is caused by thermal fluctuations in magnetization, so that it becomes more dominant as devices become smaller, and exceeds 200 Gbpsi to 300 Gbpsi for electrical noise. It is considered to be. In order to avoid magnetic white noise and further increase the recording density of magnetic recording, a micromagnetic sensor that operates on a principle different from the conventional magnetoresistive effect is required. Development of effect elements is underway (for example, see Non-Patent Document 1).
R. Sato, et. Al. J. Magn. Magn. Mat. Vol. 279, p. 36 (2004)

  A conventional resonant magnetoresistive effect element uses an artificial antiferromagnet having a small number of defects as a magnetic body having a structure in which a nonmagnetic layer having a thickness of 1 nm or less is sandwiched between ferromagnetic layers having a perpendicular magnetization direction. We have attempted to improve the characteristics by increasing the strength of the effective high-frequency magnetic field. However, since this artificial antiferromagnetic material requires advanced film formation technology, it has many difficulties in practical use. For this reason, sufficient characteristics are not currently obtained.

  As described above, a new magnetic sensor using the resonant magnetoresistive effect is being developed to solve the magnetic white noise problem, which is a major problem in high-density magnetic recording. The characteristic is not acquired.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic sensor, a magnetic head, and a magnetic recording / reproducing apparatus that can suppress magnetic white noise as much as possible.

  The resonant magnetoresistive element according to the first aspect of the present invention includes a first magnetic layer whose magnetization direction is substantially parallel to the film surface, and a second magnetic layer whose magnetization direction is substantially perpendicular to the film surface. And a first nonmagnetic layer provided between the first and second magnetic layers.

The resonant magnetoresistive effect element according to the second aspect of the present invention is provided between the first and second magnetic layers whose magnetization directions are substantially parallel to the film surface, and the first and second magnetic layers, A third magnetic layer having a magnetization direction substantially perpendicular to the film surface; and a laminated film in which a plurality of nonmagnetic layers are laminated.
A magnetic head according to a third aspect of the present invention is characterized in that the resonant magnetoresistive element is mounted as a reproducing element.
A magnetic recording / reproducing apparatus according to the fourth aspect of the present invention includes the above magnetic head.

  According to the present invention, magnetic white noise can be suppressed as much as possible.

  First, before describing an embodiment of the present invention, a resonant magnetoresistive element, which is a kind of magnetic transmission element, will be described. Resonant magnetoresistive elements actively utilize thermal fluctuations of magnetization that are unavoidable in soft magnetic materials, and are characterized by injecting spin fluctuations of conduction electrons caused by thermal fluctuations of magnetization of ferromagnetic materials into magnetic materials. To do. The spin fluctuation of the injected conduction electrons acts as an effective high-frequency magnetic field on the magnetic material through an interaction such as sd exchange interaction, and induces magnetic resonance in the magnetic material. When the external magnetic field changes and the fluctuation of the ferromagnetic magnetization changes, the intensity of magnetic resonance induced in the magnetic substance changes. This change is detected as a change in the effective electrical resistance of the magnetic substance. By such a principle, an element resistance change of several 10% to several 100% is obtained with respect to an external magnetic field change of about 10 Oersteds, and functions as a minute high sensitivity magnetic sensor.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to the common components, and duplicate descriptions are omitted. Each figure is a schematic diagram, and its shape, dimensions, ratio, etc. include parts that are different from the actual device. However, when actually manufacturing elements etc., the following explanation and consideration of known techniques are considered. Can be changed as appropriate.

(First embodiment)
The configuration of the resonant magnetoresistive element according to the first embodiment of the present invention is shown in FIG. FIG. 1 is a cross-sectional view showing the configuration of the resonant magnetoresistive element according to the present embodiment. The resonant magnetoresistive element according to the present embodiment is provided on the substrate 1 and has a lower electrode 3 that also serves as a magnetic shield, and a ferromagnetic that is provided on the lower electrode 3 and whose magnetization direction is substantially perpendicular to the film surface. A layer 5, a nonmagnetic layer 7 provided on the ferromagnetic layer 5, a ferromagnetic layer 9 provided on the nonmagnetic layer 7 and having a magnetization direction substantially parallel to the film surface, and a ferromagnetic layer 9 And an upper electrode 11 also serving as a magnetic shield. The ferromagnetic layer 5, the nonmagnetic layer 7, and the ferromagnet 9 are the laminated films 4 having the same planar shape. The ferromagnetic layer 5 has a magnetization direction substantially perpendicular to the film surface, that is, a direction in which the easy axis is perpendicular to the film surface, and the ferromagnetic layer 9 has a magnetization direction substantially parallel to the film surface, that is, magnetization. The easy axis is a direction parallel to the film surface. In this embodiment, “substantially vertical” includes an inclination of ± 15 degrees from a completely vertical state, and “substantially parallel” means ± 15 from a completely parallel state. Includes a degree tilt.

  Since the lower electrode 3 and the upper electrode 11 also serve as wiring, the lower electrode 3 and the upper electrode 11 extend in the horizontal direction in FIG. 1, and are connected to a current supply circuit, a reading (sense) circuit, or the like that controls the current flowing through the element at the end. The The lower electrode 3 and the upper electrode 11 also serve as a magnetic shield and a wiring. However, the magnetic shield and the wiring can be provided separately from the lower electrode and the upper electrode. Also in this case, the magnetic shield and the wiring may be formed in a plane parallel to the film surfaces of the lower electrode 3, the upper electrode 11, and the ferromagnetic layer 9 (in the plane extending in the left-right direction on the paper surface in the cross section of FIG. 1). it can.

The resonant magnetoresistive element according to the present embodiment positively utilizes thermal fluctuations of magnetization that are unavoidable in ferromagnetic materials. That is, the spin fluctuation of conduction electrons caused by the thermal fluctuation of the magnetization of the ferromagnetic layer 9 is injected into the ferromagnetic layer 5 through the nonmagnetic layer 7. Spin fluctuation of the injected conduction electrons, induce magnetic resonance, such as over a sd exchange interaction acts as an effective high frequency magnetic field to exert a spin torque to the ferromagnetic layer 5, a ferromagnetic layer 5 in the threshold current I _th or To do. When the external magnetic field changes and the fluctuation spectrum of the magnetization of the ferromagnetic layer 9 changes, the intensity of magnetic resonance induced in the ferromagnetic layer 5 changes. This intensity change depends on the effective electrical resistance of the resonant magnetoresistive element. Is detected as a change. According to such a principle, a device resistance change of several hundreds to several thousand% can be obtained with respect to a change of an external magnetic field of several tens of Oersted (Oe).

  Thus, the resonant magnetoresistive effect element of this embodiment functions as a minute high-sensitivity magnetic sensor. As will be described in detail later, the resonant magnetoresistive element of the present embodiment uses thermal fluctuations in magnetization of the ferromagnetic layer 9 and the ferromagnetic layer 5, so that the junction area (ferromagnetic layer 5, nonmagnetic layer 7, Even if the junction area between the ferromagnetic layers 9 is reduced, the sensitivity and the SN ratio are hardly reduced. Therefore, when applied to a magnetic head for reproducing magnetic information, it is possible to cope with ultra-high density recording in which the recording density exceeds several hundred Gbpsi to 1 Tbpsi.

In this embodiment, assuming that a read magnetic head compatible with 1 Tb / inch ² is assumed as an example of the ferromagnetic layer, the ferromagnetic layer 9 has a plane area of about 30 × 30 nm ² and a thickness of about 1 nm. The ferromagnetic layer 5 and the nonmagnetic layer 7 can have the same plane area as the ferromagnetic layer 9. That is, the junction area of the resonant magnetoresistive element of this embodiment is about 30 × 30 nm ² . In this embodiment, the laminated film 4 composed of the ferromagnetic layer 5, the nonmagnetic layer 7, and the ferromagnetic layer 9 is formed so as to form a column with a square bottom surface, and the four side surfaces thereof are nonmagnetic insulators. (Not shown). The shape of the laminated film 4 can be appropriately changed to other shapes such as a circular cylinder with a bottom surface, a triangular prism with a triangular bottom surface, and a polygonal column with a polygonal bottom surface.

Examples of the material of the ferromagnetic layer 9 include Fe, Co, Ni, and alloys thereof, Heusler alloys such as Cu ₂ MnAl, Ni ₂ MnIn, Cu ₂ MnIn, Cu ₂ MnSn, Ni ₂ MnSn, and Co ₂ MnSn, Fe ₃ Conductive magnetic compounds such as O ₄ and LaSrMnO ₃ can be used. However, since the magnitude of the thermal fluctuation of the magnetization is inversely proportional to the volume of the magnetic material and the square root of the magnetization as will be shown later, a ferromagnetic material having a magnetization of 1000 G or less and a thickness of 0.1 nm to 3 nm is preferable. As a material of the nonmagnetic layer 7, a noble metal such as Al, Pt, Au, Ag, or Cu, or a nonmagnetic transition metal such as Cr, Ru, or Pd can be used. The thickness of the nonmagnetic layer 7 can be about 1 nm to several tens of nm, for example, about 5 nm. The nonmagnetic layer 7 serves to block the exchange interaction between the ferromagnetic layer 9 and the ferromagnetic layer 5 and simultaneously transport the spin fluctuation of the conduction electrons generated in the ferromagnetic layer 9 to the ferromagnetic layer 5. I'm in charge.

  As the material of the ferromagnetic layer 5, for example, hexagonal Co can be used. When Co is used, the vertical anisotropy magnetic field (vertical anisotropy constant) can be changed by controlling the type and film thickness of the underlying metal. In order to resonate with magnetic fluctuations of several GHz to several tens of GHz generated by the ferromagnetic layer 9, the magnitude of the perpendicular anisotropic magnetic field is desirably 1 kOe or more. Other than Co as the material of the ferromagnetic layer 5, CoCr alloys such as CoCrTa, CoCrTaPt, and CoCrTaNb, Co multilayer films such as Co / Pd, Co / Pt, and Co—Cr—Ta / Pd, CoCrPt alloys, and FePt alloys Furthermore, rare earth-containing SmCo alloys and TbFeCo alloys can be used. The thickness of the ferromagnetic layer 5 is preferably 0.1 to 3 nm for the reason described later.

As the material of the lower electrode 3 and the upper electrode 11, a metal such as Al, Cu, Au, Ag, Ru is used. In particular, when Co is used as the ferromagnetic layer 5, it is preferable to use Ru. When the lower electrode 3 and the upper electrode 11 also serve as a magnetic shield, a laminated film is formed of the above-described metal film and a known shield material film such as NiFe. For the substrate 1, a substrate material generally suitable for forming a magnetic element, such as a substrate of nonmagnetic insulator such as silicon or SiO ₂ / Al ₂ O ₃ / TiC, is used.

Next, the thermal fluctuation of magnetization in the ferromagnetic layer 9 will be described. FIG. 2A is a diagram schematically showing a power spectrum S _<mt> of thermal fluctuation of the ferromagnetic layer 9. FIG. 2B shows the magnetization component in the film surface of the ferromagnetic layer 9, where M _s is the saturation magnetization of the ferromagnetic layer 9, and M _t is the transverse magnetization perpendicular to the saturation magnetization of the magnetization of the ferromagnetic layer 9. It is an ingredient. Which is the ratio of the M _t and the saturation magnetization M _s m _t represents the angle (radian) of the thermal fluctuation of the magnetization of the ferromagnetic layer 9. The thermal fluctuation of the magnetization of the ferromagnetic layer 9 at the temperature T (Kelvin) is approximately (1) using the power spectrum S _<mt> of the root mean square <m _t ² > of m _t (= M _t / M _s ). )

In the equation (1), χ ″ _FM is the imaginary part of the high-frequency magnetic susceptibility of the ferromagnetic layer 9, V _FM is the volume of the ferromagnetic layer 9, α is the Gilbert attenuation coefficient of the ferromagnetic layer 9, and γ (= 19 × 10 ⁶ rad / SOE) is the gyromagnetic _{ratio, f FM} is the resonant frequency of the ferromagnetic layer 9, H is the external magnetic field, H _K of the ferromagnetic layer 9 undergoes an anisotropy field of the ferromagnetic layer 9. (1) From the equation and FIG. 2A, when the external magnetic field frequency f is in the vicinity of the resonance frequency f _FM , the high-frequency magnetic susceptibility χ ″ _FM increases and the power spectrum S _<mt> of the magnetization fluctuation of the ferromagnetic layer 9 also increases. I understand. The value of S _{<mt> at} the peak frequency f _FM is inversely proportional to the volume V _FM and the saturation magnetization M _s . When a permalloy (saturated magnetization M _s = 800 Gauss) having a volume V _FM of about 30 × 30 × 1 nm ³ is used as the ferromagnetic layer 9, assuming that the resonance frequency f ₀ = 10 GHz and Gilbert's attenuation coefficient α = 0.01, The thermal fluctuation <m _t ² > ^1/2 of the magnetization of the ferromagnetic layer 9 at the frequency f = f _FM of the external magnetic field and the bandwidth Δf is _{expressed by} equation (2).

と表され、Δｆ＝５．６×１０^８Ｈｚである。 Here, the bandwidth Δf is the full width at half maximum of the resonance line of the ferromagnetic layer 9.

And Δf = 5.6 × 10 ⁸ Hz.

In the conduction electrons in the ferromagnetic layer 9 having such magnetization fluctuations, spin fluctuations caused by thermal fluctuations in the magnetization of the ferromagnetic layer 9 occur. The conduction electrons having the spin fluctuation are transported by the current flowing through the laminated film 4 composed of the ferromagnetic layer 9 / nonmagnetic layer 7 / ferromagnetic layer 5, pass through the nonmagnetic layer 7 and injected into the ferromagnetic layer 5. The The spin fluctuation of the injected conduction electrons applies a high frequency torque (effective high frequency magnetic field) to the ferromagnetic layer 5 through sd exchange interaction and the like, and induces magnetic resonance in the ferromagnetic layer 5. The torque that the spin s exerts on the magnetic material is expressed by equation (3).

In equation (3), bold M is a magnetization vector of the ferromagnetic layer 5, and M hat and s hat are a magnetization vector M and a unit vector in the spin s direction. h = (h ₁ ² + h ₂ ² ) ^1/2 is the magnitude of the effective magnetic field. h depends on the current density j, the spin polarizability p of the current, the thickness d of the ferromagnetic layer 5, and the magnetization M which is the magnitude of the magnetization vector. As the thickness d is thinner and the magnetization M is smaller, h becomes larger. Therefore, it is desirable that the thickness d is 0.1 nm or more and 3 nm or less, and the magnetization M is 1000 G or less. The spin polarizability p of the current is about 0.8, and when d = 1 nm and M = 1000 G, h = 10 ⁻⁴ j (Oe) at a current density of j (A / cm ² ).

From the equation (3), the power spectrum of the high-frequency magnetic field generated by the spin fluctuation <m _t ² > is G (f) = h ² S _<mt> .

The imaginary part of the magnetic susceptibility of the ferromagnetic layer 5 is expressed by equation (4).

In Equation (4), f ₀ is the resonance frequency of the ferromagnetic layer 5, H _A is the anisotropic magnetic field, α ′ is the Gilbert damping constant of the ferromagnetic layer 5, and Co of H _A −4πM = 3500 (Oe) Is used for the ferromagnetic layer 5, f ₀ ≈10 GHz.

When the thermal fluctuation of the magnetization of the ferromagnetic layer 5 whose direction of magnetization is perpendicular to the film surface is small and can be ignored as in the case of normal ferromagnetic resonance, the resonance frequency of the ferromagnetic layer 5 and the ferromagnetic layer 9 should be equal. The above-described high-frequency magnetic field can induce magnetic resonance in the ferromagnetic layer 5 regardless of its magnitude. However, in the present element, the thermal fluctuation of the ferromagnetic layer 5 is large and is about the same as the thermal fluctuation of the ferromagnetic layer 9. The thermal fluctuation of magnetization in the ferromagnetic layer 9 and the ferromagnetic layer 5 has no phase correlation, and the phase correlation time is also about 1 / (αf _FM ) = 1 / (α′f _PFM ), so the high frequency magnetic field is small. In some cases, no energy absorption occurs when time averaged. However, when the current increases, the high-frequency magnetic field increases in proportion thereto, so that the movement of the magnetization M of the ferromagnetic layer 5 is dominated by the high-frequency magnetic field, and finally becomes in phase with the high-frequency magnetic field and energy absorption occurs. When h = h ₀ · j, when the thicknesses of the ferromagnetic layer 9 and the ferromagnetic layer 5 are equal, the threshold current density at which resonance absorption occurs is expressed by equation (5).

In the case of p = 0.8, M = 1000 G, and d = 1 nm, it is estimated that h ₀ = 1.4 × 10 ⁻⁴ Oe / (A / cm ² ), so that the critical current density j _th is j _th = 2. 8 × 10 ⁴ A / cm ² . h ₀ can cause a resonance absorption at a low threshold current density as a thin film thickness is inversely proportional to the thickness of the magnetic layer. The threshold current for the h ₀ is dependent on the film thickness depends on the thickness of the ferromagnetic layer 9 and the ferromagnetic layer 5, but does not depend on the element area as seen from the equation (5).

Since the current density j is a critical current density j _th least fluctuation of the ferromagnetic layer 5 is in the same phase and fluctuations of the ferromagnetic layer 9, the fluctuation of the ferromagnetic layer 9 by the high-frequency torque further increases. That is, when j> j _th , a positive feedback loop is formed between the magnetization of the ferromagnetic layer 5 and the magnetization movement of the ferromagnetic layer 9, and the amplitude of the fluctuation increases until it becomes substantially equal to the magnitude M of the magnetization.

The resonance absorption power in the ferromagnetic layer 5 when the current density j is _{equal to} or greater than the _sea current density jth can be evaluated by the equation (6).

M = 1000G, V _PFM = 30 × 30 × 1 nm ³ , h = 1.4 × 10 ⁻⁴ × j O
Substituting e, the absorption at j = j _th = 2.8 × 10 ⁴ A / cm ² is _WPFM = 1.1 × 10 ⁻⁴ erg / s = 1.1 × 10 ⁻¹¹ watts. Taking in the effect that the high frequency torque accompanying the fluctuation of the ferromagnetic layer 5 acts on the ferromagnetic layer 9 and adding the same amount of absorption in the ferromagnetic layer 9, W = 2.2 × 10 ⁻¹¹ as the absorption W of the entire element. Watts are obtained. The element voltage and resistance are such that the plane area of the element is A = 30 × 30 nm ² , and _therefore , ΔV = W / I _th = 0.I at _{I≈I th} = j _th · A = 2.5 × 10 ⁻⁷ A. 88 × 10 ⁻⁴ V and ΔR = ΔV / I _th = 350Ω. Absorbing power at _{I> I th} remains ΔV is constant because increases in proportion to the current as W = 8.8 × ^{10 -5} I. The resistance R ₀ at non-resonance is about 5Ω when the interface resistance is 1.0 × 10 ⁻¹¹ Ωcm ² and the average bulk resistance is 5 × 10 ⁻⁶ Ωcm, so ΔR (I _th ) / R ₀ to 70 (7000) %).

From the expression (1), the peak frequency f _FM of the fluctuation power spectrum of the micromagnetic material changes as shown in the expression (7) due to the change δH of the external magnetic field, but the resonance frequency of the perpendicular magnetization film is H << _HA = Almost no change at 3500 Oe.

  That is, the element changes from a resonance state to a non-resonance state by applying an external magnetic field, and the output voltage ΔV decreases.

  The characteristics of the resonant magnetoresistive element of this embodiment are shown in FIG. When the external magnetic field changes and the resonant magnetoresistive element changes from the resonance state to the non-resonance state, the threshold current changes as indicated by the dotted line, and the output voltage changes significantly as indicated by the arrow.

The resonant magnetoresistive element of this embodiment uses thermal fluctuations of magnetization, and the characteristics thereof are the relative magnitude of thermal fluctuations in the ferromagnetic layer 9 and the ferromagnetic layer 5 in which the magnetization direction is perpendicular to the film surface. Depends on. For this reason, as long as each film has a single domain structure, it functions independently of the element size. However, since as the size of the magnetic material is small magnetic layer of a single-domain structure can be easily obtained, it is desirable that the element size of 1 [mu] m ² or less. In addition, in the temperature range where the cutoff frequency kT / h (k: Boltzmann constant, T: temperature, h: Planck constant) of the thermal fluctuation is sufficiently higher than the resonance frequency, the temperature dependence of the characteristics is small, so the thermal fluctuation is generally small. It operates even at low temperatures.

Next, electrical and magnetic noise of the resonant magnetoresistive element according to the present embodiment will be described. The resonant magnetoresistive element shown in FIG. 1 includes a large number of ferromagnetic and nonmagnetic interfaces. However, since the total voltage V ₀ applied to the element is about several mV, the relationship of eV ₀ << kT is established, As the noise, the thermal noise _vel expressed by the equation (8) becomes dominant.

Here, B is a bandwidth. The magnetic white noise of this element is 0.1 μV or less and can be ignored. _{B = 300MHz, R 0 = 5Ω} , if the [Delta] V = 0.1 mV, SN ratio (SNR) is expressed as SNR = ΔV / v _el, the SNR = 20 (26dB).

  As described above, according to the present embodiment, magnetic white noise can be suppressed as much as possible.

  When the resonant magnetoresistive element of this embodiment is used as a reproducing element of a magnetic head, as shown in FIG. 8, the side of the laminated film 4 composed of the ferromagnetic layer 5, the nonmagnetic layer 7, and the ferromagnetic layer 9 is used. It is necessary to provide the horizontal magnetization bias film 20 in the part.

(Second Embodiment)
In the first embodiment, the ferromagnetic layer 9 and the ferromagnetic layer 5 whose magnetization direction is substantially perpendicular to the film surface are each a single layer, and one laminated film 4 formed via the nonmagnetic layer 7 is provided. It was a resonance magnetoresistive effect element.

  The resonant magnetoresistive effect element according to the present embodiment has a structure in which a plurality of stacked films 4 according to the first embodiment are stacked. By laminating a plurality of the laminated films of the first embodiment, spin fluctuations caused by the ferromagnetic layer whose magnetization direction is substantially parallel to the film surface are sequentially applied to the ferromagnetic layer whose magnetization direction is perpendicular to the film surface. By inducing resonance, a larger output voltage ΔV can be obtained. As shown in FIG. 4A, a ferromagnetic layer 5 whose magnetization direction is substantially perpendicular to the film surface, a ferromagnetic layer 9 whose magnetization direction is substantially parallel to the film surface, and a nonmagnetic layer 7 However, as shown in FIG. 4B, the magnetization direction is between the two ferromagnetic layers 9 substantially parallel to the film surface and the magnetization direction is on the film surface. Even when a plurality of substantially perpendicular ferromagnetic layers 5 are laminated via the nonmagnetic layer 7, the output voltage can be increased as compared with the first embodiment.

  This embodiment can also suppress magnetic white noise as much as possible as in the first embodiment.

(Third embodiment)
Next, a resonant magnetoresistive element according to a third embodiment of the invention will be described with reference to FIG. The resonant magnetoresistive element of this embodiment has a configuration in which a perpendicular magnetization bias film 22 is provided between the ferromagnetic layer 9 and the upper electrode 11 in the resonant magnetoresistive element of the first or second embodiment. Yes.

In the first and second embodiments, a change in the external magnetic field applied in the plane of the ferromagnetic layer 5 is detected as a change in the resonance frequency of the ferromagnetic layer 5 expressed by equation (7). In the embodiment, it is detected as a change in the resonance frequency of the ferromagnetic layer 9. Magnetization is greater the smaller the difference between the vertical direction of the crystal anisotropy field H _A in magnetic field change the shape anisotropy field 4πM the film surface of the resonant frequency of the vertical ferromagnetic layer 5. For this reason, when the resonant magnetoresistive element of this embodiment is used as a sensor, 0 Oe ≦ ( _HA −4πM ) ≦ 500 Oe. In the ferromagnetic layer 9 as well, the magnetic field change in the direction perpendicular to the film surface can be detected by reducing the difference between the shape anisotropy field 4πM _s and the crystal anisotropy magnetic field H _A1 in the direction perpendicular to the film surface. However, in order to have high sensitivity, it is desirable that 0Oe ≦ (4πM _s −H _A1 ) ≦ 500 Oe. In this case, higher sensitivity can be obtained by causing the magnetic layer 9 to function as a sensor in a state in which the magnetization direction of the magnetic layer 9 is substantially perpendicular to the film surface by the bias magnetic field from the perpendicular magnetization bias film 22.

  In this embodiment, the perpendicular magnetization bias film 22 is provided between the ferromagnetic layer 9 and the upper electrode 11. However, as shown in FIG. 10, the ferromagnetic layer 5, the nonmagnetic layer 7, and the ferromagnetic layer are provided. The perpendicular magnetization bias film 24 may be provided on the side of the laminated film 4.

(Fourth embodiment)
Next explained is a magnetic recording / reproducing apparatus according to the fourth embodiment of the invention. A magnetic head provided with the resonant magnetoresistive effect element according to the first to third embodiments described with reference to FIGS. 1 to 10 as a reproducing element is incorporated into a recording / reproducing integrated magnetic head assembly, for example, in a magnetic recording / reproducing apparatus. Can be installed.

  FIG. 11 is a perspective view of a main part illustrating the schematic configuration of such a magnetic recording / reproducing apparatus. That is, the magnetic recording / reproducing apparatus 150 according to the present embodiment is an apparatus using a rotary actuator. In the figure, a magnetic disk 200 for longitudinal recording or perpendicular recording is mounted on a spindle 152 and rotated in the direction of arrow A by a motor (not shown) that responds to a control signal from a drive device control unit (not shown). The magnetic disk 200 has a recording layer for longitudinal recording or perpendicular recording. In the magnetic disk 200, a head slider 153 that records and reproduces information stored in the magnetic disk 200 is attached to the tip of a thin film suspension 154. Here, the head slider 153 has a magnetic head equipped with the resonant magnetoresistive element according to any one of the above-described embodiments as a reproducing element mounted near the tip thereof.

  When the magnetic disk 200 rotates, the medium running surface (ABS) of the head slider 153 is held with a predetermined flying height from the surface of the magnetic disk 200.

  The suspension 154 is connected to one end of an actuator arm 155 having a bobbin portion for holding a drive coil (not shown). A voice coil motor 156, which is a kind of linear motor, is provided at the other end of the actuator arm 155. The voice coil motor 156 is composed of a drive coil (not shown) wound around the bobbin portion of the actuator arm 155, and a magnetic circuit composed of a permanent magnet and a counter yoke arranged so as to sandwich the coil.

  The actuator arm 155 is held by ball bearings (not shown) provided at two locations above and below the fixed shaft 157, and can be freely rotated and slid by a voice coil motor 156.

  FIG. 12 is an enlarged perspective view of the magnetic head assembly ahead of the actuator arm 155 as viewed from the disk side. That is, the magnetic head assembly 160 includes an actuator arm 155 having, for example, a bobbin portion that holds a drive coil, and a suspension 154 is connected to one end of the actuator arm 155.

  A head slider 153 including any of the magnetic heads described above is attached to the tip of the suspension 154. A reproducing head may be combined. The suspension 154 has a lead wire 164 for writing and reading signals, and the lead wire 164 and each electrode of the magnetic head incorporated in the head slider 153 are electrically connected. In the figure, reference numeral 165 denotes an electrode pad of the magnetic head assembly 160.

  Next, examples of the present invention will be described.

Example 1
Next, the configuration of the resonant magnetoresistive element according to Example 1 of the present invention is shown in FIG. FIG. 5 is a cross-sectional view showing the configuration of this embodiment. The resonant magnetoresistive element of the present example is manufactured as follows.

  A laminated film was formed on the sapphire substrate 1 using sputtering film formation and electron beam lithography. The laminated film includes, in order from the substrate 1 side, a nonmagnetic layer 3 made of Ru, a ferromagnetic layer 5 made of Co, a nonmagnetic layer 7 made of Cu, a ferromagnetic layer 9 made of Fe, and a nonmagnetic layer 13 made of Cu. , Ta nonmagnetic layer 15 and Cu nonmagnetic layer.

The thickness of each layer is about 100 nm for the Ru layer 3, about 1 nm for the Co layer 5, about 10 nm for the Cu layer 7, about 1 nm for the Fe layer 9, about 10 nm for the Cu layer 13, about 20 nm for the Ta layer 15, Cu layer 11 was about 100 nm. Each junction area of the ferromagnetic Co layer 5 and Fe layer 9 and the nonmagnetic Cu layers 7 and 13 was about 100 × 100 nm ^2, and SiO ₂ was used for the interlayer insulating film.

  The Co layer 5 is a ferromagnetic layer whose magnetization direction is substantially perpendicular to the film surface, and the formation of the Fe layer 9 which is a ferromagnetic layer whose magnetization direction is substantially parallel to the film surface is a magnetic field of about 1000 Oe. Magnetic uniaxial anisotropy was imparted by applying the film in a direction parallel to the film surface. The magnetic characteristics of the Co layer 5 and the Fe layer 9 are a laminated film made of Ru layer 3 / Co layer 5 / Cu layer 7 and a laminated film made of Cu layer 7 / Fe layer 9 / Cu layer 13 prepared under the same conditions as the element production. Was measured by magnetization measurement and ferromagnetic resonance measurement. The magnetization of the Co layer 5 was 920 G, the magnitude of the anisotropic magnetic field perpendicular to the film surface was 3500 Oe, the magnetization of the Fe layer 9 was 1050 G, and the magnitude of the anisotropic magnetic field parallel to the film surface was 410 Oe. .

The resonance frequency of the Co layer 5 is 9.8 GHz, and the Fe layer 9 has a resonance frequency of 9.55 GHz by adjusting a bias magnetic field in the film surface. The off-state resistance R ₀ is 1Ω, the threshold current is 1.4 μA, the resonance voltage ΔV is 0.12 mV, and the on-state effective resistance is (ΔV / I _th ) + R ₀ = 87Ω. When an external magnetic field is applied to the resonant magnetoresistive effect element of this embodiment with a current of 2 μA flowing, the resonant frequency of the Fe layer 9 changes, so that ΔV changes as shown in FIG. 6 and functions as a magnetic sensor. I understood it.

(Example 2)
Next, FIG. 7 shows the configuration of a resonant magnetoresistive element according to Example 2 of the present invention. FIG. 7 is a cross-sectional view showing the configuration of the resonant magnetoresistive element of this example. The resonant magnetoresistive effect element of this example has a structure in which the laminated structure of the ferromagnetic layer 5, the nonmagnetic layer 7, and the ferromagnetic layer 9 of Example 1 is laminated for two periods. The resonant magnetoresistive element of the present example is manufactured as follows.

As in the case of Example 1, a laminated film was formed on the sapphire substrate 1 using sputtering film formation and electron beam lithography. This laminated film includes a nonmagnetic layer 3 made of Ru in order from the substrate 1, a ferromagnetic layer 5 _{1 made of} Co, a nonmagnetic layer 7 _{1 made of} Cu, a ferromagnetic layer 9 _{1 made of} NiFe, and a nonmagnetic layer made of Cu. 7, a ferromagnetic layer 5 _{2 made of} Co, a nonmagnetic layer 7 _{2 made of} Cu, a ferromagnetic layer 9 _{2 made of} NiFe, a nonmagnetic layer 13 made of Cu, a nonmagnetic layer 15 made of Ta, and a nonmagnetic layer made of Cu A magnetic layer 11 is provided.

The thickness of each layer, Ru layer 3 is about 100 nm, Co layer ₅ 1, _{5 2} is about 1 nm, Cu layer ₇ 1, 7, 7 ₂ of about 5 nm, NiFe layer ₉ 1, _{9 2} of about 1 nm, Cu layer 13 is about 10 nm, Ta layer 15 is about 20 nm, and Cu layer 11 is about 100 nm. The element size was about 100 × 100 nm ² and SiO ₂ was used for the interlayer insulating film.

The Co layers 5 ₁ and 5 ₂ are magnetic films whose magnetization direction is substantially perpendicular to the film surface, and the formation of NiFe layers 9 ₁ and 9 ₂ that are magnetic films whose magnetization direction is substantially parallel to the film surface. Gave a magnetic uniaxial anisotropy by applying a magnetic field of about 1000 Oe in parallel to the film surface. The magnetic properties of the Co layers 5 ₁ , 5 ₂ and the NiFe layers 9 ₁ , 9 ₂ are the same as those of the element fabrication: Ru layer 3 / Co layer 5 ₁ / Cu7 ₁ layer stack film and Cu layer 7 ₁ / NiFe layer It investigated by the magnetization measurement and the ferromagnetic resonance measurement of the laminated film of 9 ₁ / Cu layer 7. Magnetization of the Co layer _{5 1} 920G, the magnitude of the perpendicular anisotropy field to the film plane is 3500 Oe, the magnetization of the NiFe layer _{9 1} 810G, the magnitude of the in-plane anisotropy field was 220Oe.

Resonance frequency of the Co layer ₅ 1, _{5 2} is 9.8 GHz, NiFe layer ₉ 1, _{9 2} was 9.6GHz resonant frequency by adjusting a bias magnetic field to the film plane. The off-state resistance R ₀ is 1.3Ω, the threshold current is 1.8 μA, the resonance voltage ΔV is 0.21 mV, and the on-state effective resistance is (ΔV / I _th ) + R ₀ = 118Ω, increasing the number of layers. As a result, the resonance voltage could be increased.

(Example 3)
A device having the same structure was produced in the same manner as in Example 1, except that the 1 nm thick Fe layer in Example 1 was replaced with a 1.2 nm thick Co film (in-plane magnetic film). From the magnetization measurement, it was found that the difference (4πM _s −H _A1 ) between the shape anisotropy field 4πM _s of this Co film and the crystal anisotropy field H _A1 perpendicular to the film surface was 350 Oe. When a bias magnetic field of 500 Oe was applied to this element in a direction perpendicular to the film surface, and a current was passed with the magnetization of the Co layer having a thickness of 1.2 nm perpendicular to the film surface, a resonance voltage of 0.15 mV at 2 μA or more. Was observed. Furthermore, when an external magnetic field was applied in the direction opposite to the bias magnetic field, it was observed that the resonance voltage was reduced to 0.5 mV by applying a magnetic field of 30 Oe, and this element can also function as a magnetic sensor for a magnetic field perpendicular to the film surface. confirmed.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to these, and various modifications can be made within the scope of the gist of the invention described in the claims.

  In addition, the present invention can be variously modified without departing from the scope of the invention in the implementation stage.

  As described above, the resonant magnetoresistive effect element of this embodiment can be manufactured by using a normal film forming technique, and the sensitivity and SN ratio are not reduced even if the junction area of the element is reduced. It is possible to realize high density and high magnetoresistance change.

Sectional drawing which shows the resonant magnetoresistive effect element by 1st Embodiment of this invention. The figure explaining the power spectrum of the thermal fluctuation of magnetization of a ferromagnetic. The figure which shows the element characteristic of the resonant magnetoresistive effect element by 1st Embodiment. Sectional drawing which shows the resonant magnetoresistive effect element by 2nd Embodiment of this invention. Sectional drawing which shows the resonance magnetoresistive effect element by Example 1 of this invention. The figure which shows that the resistance value of the resonant magnetoresistive effect element by Example 1 depends on an external magnetic field. Sectional drawing which shows the resonant magnetoresistive effect element by Example 2 of this invention. Sectional drawing which shows the resonance magnetoresistive effect element by the modification of 1st Embodiment. Sectional drawing which shows the resonant magnetoresistive effect element by 3rd Embodiment of this invention. Sectional drawing which shows the resonance magnetoresistive effect element by the modification of 3rd Embodiment. FIG. 2 is a perspective view of a main part showing a schematic configuration of a magnetic recording / reproducing apparatus. The enlarged perspective view which looked at the magnetic head assembly ahead from an actuator arm from the disk side.

Explanation of symbols

1 Substrate 3 Lower electrode 5 Ferromagnetic layer 7 Nonmagnetic layer 9 Ferromagnetic layer 11 Upper electrode

Claims (13)

A first magnetic layer having a magnetization direction parallel to the film surface, a second magnetic layer that is a single magnetic body having a magnetization direction perpendicular to the film surface, and the first and second magnetic layers. A laminated structure in which a plurality of laminated films having the first nonmagnetic layer are laminated via the second nonmagnetic layer ;
A first electrode provided on one end face side in the stacking direction of the laminated structure and electrically connected to the one end face;
A second electrode provided on the other end face side in the stacking direction of the stacked structure and electrically connected to the other end face;
A perpendicular magnetization bias film provided between the stacked structure and the first electrode;
And applying a current in a direction from the second magnetic layer to the first magnetic layer, thereby injecting spin fluctuations of the first magnetic layer into the second magnetic layer to cause magnetic resonance in the second magnetic layer. Inductive magnetic sensor. A first magnetic layer having a magnetization direction parallel to the film surface, a second magnetic layer that is a single magnetic body having a magnetization direction perpendicular to the film surface, and the first and second magnetic layers. A laminated structure in which a plurality of laminated films having the first nonmagnetic layer are laminated via the second nonmagnetic layer;
A horizontal magnetization bias film provided on a side of the laminated structure ;
And applying a current in a direction from the second magnetic layer to the first magnetic layer, thereby injecting spin fluctuations of the first magnetic layer into the second magnetic layer to cause magnetic resonance in the second magnetic layer. Inductive magnetic sensor. A first magnetic layer having a magnetization direction parallel to the film surface, a second magnetic layer that is a single magnetic body having a magnetization direction perpendicular to the film surface, and the first and second magnetic layers. A laminated structure in which a plurality of laminated films having the first nonmagnetic layer are laminated via the second nonmagnetic layer;
A perpendicular magnetization bias film provided on a side of the laminated structure ;
And applying a current in a direction from the second magnetic layer to the first magnetic layer, thereby injecting spin fluctuations of the first magnetic layer into the second magnetic layer to cause magnetic resonance in the second magnetic layer. Inductive magnetic sensor. The magnetic sensor according to any of claims 1 to 3, wherein the first and second magnetic layers are each monolayer. Magnetic according to any one of claims 1 to 4, characterized in that the size difference of the crystal anisotropy field of the first shape anisotropy field in the magnetic layer and the film surface in the vertical direction is less 500Oe Sensor. Magnetic according to any one of claims 1 to 5 size difference of the crystal anisotropy field of the second direction perpendicular to the shape anisotropy field and the film surface of the magnetic layer is equal to or less than 500Oe Sensor. The magnetic sensor according to any of claims 1 to 6, characterized in that one be less of the second magnetic layer and the first magnetic layer has a single domain structure. The magnetic sensor according to any one of claims 1 to 3, wherein the thickness of said first and second magnetic layer is 3nm or less, respectively. Magnetic head is characterized in that by mounting a magnetic sensor according as the reproduction device to any of claims 1 to 3.   A magnetic recording / reproducing apparatus comprising the magnetic head according to claim 9.   First and second magnetic layers whose magnetization direction is parallel to the film surface, and a third magnetic layer which is provided between the first and second magnetic layers and is a single magnetic body whose magnetization direction is perpendicular to the film surface And a laminated film in which a plurality of nonmagnetic layers are laminated, and by causing a current to flow through the first and second magnetic layers, the spin fluctuation of the first or second magnetic layer is injected into the third magnetic layer And magnetic resonance is induced in the third magnetic layer.   12. The magnetic sensor according to claim 11, wherein at least one of the first and second magnetic layers and the third magnetic layer has a single magnetic domain structure.   13. The magnetic sensor according to claim 12, wherein each of the first to third magnetic layers has a thickness of 3 nm or less.

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