JPH08288568A - Magnetic detection element - Google Patents

Abstract

PURPOSE: To obtain a high sensitivity magnetic detection element having high variation rate of impedance by composing a thin magnetic film having a specified compositional ratio. CONSTITUTION: The compositional formula of a thin magnetic film is represented by Fea Alb MIc MIId Ce Of , where a, b, c, d, e and f are the compositional ratio of atm%, MI is at least one kind of elements Zr, Hf, Nb, Ta, Mo and W, MII is at least one of elements Ag and Cu. The values of a, b, c, d, e and f satisfy the following relationships; a+b+c+d+e+f=100, 0.5<=b<=20, 2<=c<=25, 0.05<=d<=5, 0.5<=e<=25 and 0.2<=f<=6. When a magnetic detection element body comprising a thin magnetic film 1 and a ceramic substrate 2 is fixed to a printed board 3 and then the thin magnetic film 1 is soldered 4 at the opposite ends thereof, a high sensitivity magnetic detection element having high variation rate of impedance can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic detecting element utilizing the magnetic impedance effect.

[0002]

2. Description of the Related Art Conventionally, as a magnetic sensor, there is an MR (magnetoresistive effect) sensor, which has features such as being capable of detecting a weak magnetic field and being suitable for miniaturization of a shape. First, research is progressing as various measuring sensors. However, due to the anisotropic magnetoresistive effect of the ferromagnetic material used in the MR sensor, the MR ratio is as low as 5 to 6%, which hinders high density magnetic recording and high resolution of various magnetic sensors. Came. In recent years, a phenomenon in which the MR ratio is several tens of percent has been found in artificial lattice magnetic materials, and it is expected to realize a high-sensitivity magnetic sensor. However, in these operations, hysteresis depends on external magnetic field dependence of resistance. There are many problems in practical application, such as the appearance of a magnetic field, the need for applying a strong magnetic field, and the need for extremely low temperatures.

[0003]

Recently, in addition to the magnetic sensor using the magnetoresistive effect of these magnetic materials, a magnetic detecting element (hereinafter referred to as MI element) utilizing the magnetic impedance effect has been proposed.

The magneto-impedance effect is that when a high-frequency current is passed through an amorphous wire, the amplitude of the voltage across the wire is equal to several 1 with a small external magnetic field of several Gauss, as shown in FIG.
It is a phenomenon that increases by 0%. Most of the proposals for this MI element use amorphous wires,
There are few cases where a thin film is used as a magnetic material forming an element.

[0005] As one that has been announced, there is "Magnetic Impedance Effect of CoFeB Amorphous Sputtered Film" by Nagoya University, Tsuyoshi Uchiyama, Yoshitoshi Mori and others at the 1994 Applied Magnetics Society. Among them, the impedance change rate is 10% at maximum, and the sensitivity is 0.8% / Oe at the place where the change is the steepest. The magnetic thin film is more advantageous than the wire in consideration of the miniaturization of the MI element and the production of the electrodes and the lead wires, but the maximum change rate of 10% is small in the magnetic thin film type.

The thin film used for the MI element is required to have the following characteristics.

1. When incorporated in a closed magnetic circuit such as a magnetic head, the magnetic permeability in the longitudinal direction is high, and the saturation magnetic flux density is high in order to avoid saturation of magnetic flux due to miniaturization of the element.

2. It has excellent corrosion resistance that does not cause deterioration of magnetic properties under conditions of high temperature and high humidity.

3. Withstand the high temperatures of glass bonding.

4. A film having induced anisotropy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a high-sensitivity magnetic detection element which is composed of a magnetic thin film satisfying these requirements and which has a large impedance change rate.

[0012]

In order to solve the above-mentioned problems, in the first magnetic sensing element of the present invention, a, b, c,
d, e, and f represent the value of the composition ratio in atomic%, MI is at least one of the elements Zr, Hf, Nb, Ta, Mo, and W, and MII is at least one of the elements Ag and Cu. Is represented by a composition formula of Fea Alb MIc MIId Ce Of, and the respective values of a, b, c, d, e and f are: a + b + c + d + e + f = 100 0.5 ≦ b ≦ 20 2 ≦ c ≦ 25 The magnetic thin film was 0.05 ≦ d ≦ 5 0.5 ≦ e ≦ 25 0.2 ≦ f ≦ 6.

In the second magnetic detecting element, the first magnetic element
The composition of the magnetic thin film of the magnetic detection element of
The magnetic thin film has a composition in which 0.1 to 5 atomic% of at least one kind of rare earth element such as m is added.

[0014]

In the magnetic thin film of the magnetic detecting element, Zr, H
By adding Al to the Fe—C—O magnetic thin film to which at least one kind (hereinafter referred to as MI) of f, Nb, Ta, Mo and W is added, and further adding at least one of Ag and Cu. It is possible to improve the corrosion resistance without changing the coercive force, the magnetostriction and the like so much.

Further, the corrosion resistance is further improved by adding at least one kind of rare earth element such as Ce, Sm and Dy. This is Al, Cu, Ag, Ce, Sm,
This is probably because Dy and the like act on Fe so as to directly suppress oxidation.

Further, the reason why the addition amount of each element is set as described above is as follows.

With respect to Al, the range of 0.5 to 20 atomic% is a range in which corrosion resistance is improved and magnetic characteristics are not deteriorated.
It is preferably 1 to 10 atom%. When it exceeds 20 atomic%, the magnetostriction exceeds 30 × 10 ⁻⁷ and becomes large. Further, the saturation magnetic flux density also decreases. Further, if it is less than 0.5 atom%, the effect of improving the corrosion resistance cannot be obtained.

Regarding MI and C, MI and C form fine crystals of carbide, which suppress the grain growth of Fe and maintain soft magnetism up to a high temperature. If it is less, the effect is not exerted, and if it exceeds 25 atomic%, good soft magnetic properties cannot be obtained. Therefore, the above-mentioned amounts are added respectively, but more preferably MI: 3
˜15 atomic%, C: 3 to 15 atomic%.

When Ag and Cu are less than 0.05 atom%, the magnetic properties and corrosion resistance are not improved.
If it is more than 5 atomic%, the magnetic properties will deteriorate. Ag,
It is considered that Cu has an effect of refining crystal grains, and thus magnetic characteristics are improved.

O increases the electric resistance of the film and improves the high frequency characteristics, and at the same time, Al, (Ag, Cu), (Ce,
Sm, Dy, etc.) have the role of improving the corrosion resistance, but if it is less than 0.2 at%, the effect is not exhibited, and if it exceeds 6 at%, the soft magnetic properties deteriorate. Occurs.

Although rare earth elements such as Ce, Sm, and Dy have the effect of improving the corrosion resistance, the effect is not exhibited at 0.1 atom%, and if added in excess of 5 atom%, the soft magnetic characteristics deteriorate. Will end up.

Since the magnetic thin films of the first and second magnetic sensing elements of the present invention have the composition determined for the above reasons, they become microcrystalline films, exhibiting good soft magnetic characteristics and high saturation magnetic flux density. In addition, it has excellent corrosion resistance and does not cause deterioration of magnetic properties under conditions of high temperature and high humidity. It also maintains soft magnetic properties up to high temperatures, withstands high temperatures of glass bonding, and has low magnetostriction. As shown in FIG. 5, such a magnetic thin film has a large rate of change V / V (Hex = 0) in the output voltage due to the impedance change according to the external magnetic field Hex, and a highly sensitive magnetic detection element can be constructed. FIG. 5 shows the first aspect of the present invention.
Fe-Al-Nb-Ta-
Device composed of Cu—C—O thin film, Fe—Al—Nb
-Ta-Ag-C-O thin film element, and Sendust Fe-Al-Si-N thin film element as a comparative example, and 82Ni-Fe MR element as reference, respectively, output characteristics by external magnetic field Is shown.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. A non-magnetic ceramic substrate (TiO, CaO-based) for producing a sample of an MI device to which the present invention is applied
As a microcrystalline A type magnetic thin film, a thin film having a composition of Fe _66.3 Al _9.5 Ta _5.0 Nb _1.6 C _11.8 O _5.6 Ag _0.2 was formed by a facing target sputtering apparatus.

On another ceramic substrate, a composition of Fe _64.3 Al _9.5 Ta _5.0 Nb _1.6 C _11.8 O _5.6 Cu _0.2 D was _prepared as a microcrystalline B type magnetic thin film.
A thin film of y ₂ was deposited.

Further, in order to prepare a sample of the comparative example,
On another ceramic substrate, a thin film having a composition of Fe _68.5 Si _15.8 Al _9.4 N _6.3 was formed as a Sendust-based magnetic thin film.

Then, each ceramic substrate is
As shown in FIG. 1, the magnetic thin film 1 is formed into a rectangular shape with a width of 0.2 mm and a length of 8 mm and a height of 1 mm. Then, the MI element body was formed.

The magnetic thin film 1 having the same composition has a direction of easy axis of magnetization by heat treatment in a magnetic field, and a direction in which a high frequency drive current is applied to the magnetic thin film 1 for magnetic detection (an external magnetic field to be detected is applied). Direction and parallel to the longitudinal direction of the thin film 1) with anisotropy, and the easy axis of magnetization is the width direction orthogonal to the direction of application of the drive current in the film plane. One having anisotropy was prepared, and one having different anisotropy strengths Hk in the easy axis direction and the hard axis direction was prepared.

As shown in FIG. 2, each of the MI element bodies prepared in this manner is fixed to the printed circuit board 3, and both ends of the magnetic thin film 1 are connected to each other by the solder 4 to form the MI. Each of the device samples was prepared. The composition of the magnetic thin film of each sample, the saturation magnetic flux density Bs,
Table 1 below shows the film thickness, the magnetic permeability μ at 1 MHz in the longitudinal direction and the width direction, the anisotropic magnitude Hk, the coercive force Hc, and the easy axis of magnetization.

[0029]

[Table 1]

As can be seen from Table 1, the saturation magnetic flux density Bs and the magnetic permeability μ are higher than those of the Sendust thin film samples 1 and 2 in all of the microcrystalline A type samples 3 to 6 and the B type samples 7 to 12. High, low coercive force Hc, and excellent magnetic properties.

The output characteristics of samples 1 to 12 in Table 1 were measured. That is, as shown in FIG. 3, an external magnetic field is applied in the longitudinal direction of the sample 6 (longitudinal direction of the magnetic thin film 1) by the Helmholtz coil 5, and a high frequency drive current of 30 mAp-p at a frequency of 100 MHz is applied from the drive current source 7. The applied voltage was changed by ± 10 Oe, and the voltage change between the terminals at both ends was measured.

As a result, the voltage change has a curve as shown in FIG. In FIG. 4, VMAX is the maximum voltage change rate with respect to the change of the external magnetic field of ± 10 Oe, HMAX is the applied magnetic field showing the maximum voltage change, and ΔV is the voltage change rate per unit magnetic field (% /
Oe). When used as a magnetic sensor, it is advantageous that VMAX is large and ΔV is also large. V of each sample
MAx, HMAX and ΔV are shown in Table 2 below.

[0033]

[Table 2]

As can be seen from Table 2, for Sendust-based samples 1 and 2, when the easy axis of magnetization is provided in the width direction orthogonal to the drive current application direction and when the easy axis is provided in the longitudinal direction parallel to the direction. , VMAX is 18.7%,
The former is obviously larger with 2.9%. The rate of change ΔV is also larger in the former case. The applied magnetic field HMAX showing the maximum voltage change is smaller in the latter case.

Next, looking at the microcrystalline type A and B, as shown in Samples 3 and 7, VMAX, when the easy axis is attached in the width direction orthogonal to the driving current application direction,
Both ΔV are large, and VMAX is nearly 2 to 3 times that of Sendust-based samples 1 and 2. Looking at the relationship between the anisotropy magnitudes Hk and VMAX in the easy axis direction and the hard axis direction, a microcrystalline type A: sample 6 Hk 0.2 Oe → VMAX 25.4% sample 3 Hk 3.3 Oe → VMAX 28.3% Sample 5 Hk 10.0 Oe → VMAX 21.4% Microcrystalline system type B: Sample 9 Hk 0.1 Oe → VMAX 29.6% Sample 7 Hk 1.1 Oe → VMAX 50.4% Sample 12 Hk It can be seen that VMAX is large in the range of 1 to 5 Oe such as 2.3 Oe → VMAX 49.4% Sample 11 Hk 4.7 Oe → VMAX 48.0% Sample 10 Hk 12.0 Oe → VMAX 41.0%.

As described above, in the magnetic thin films of microcrystalline type A and B, induced anisotropy is provided so that the direction of easy axis of magnetization is perpendicular to the drive current application direction in the film plane, and the magnitude of the anisotropy is large. By setting Hk in the range of 1 to 5 Oe, VMax and ΔV
Can be increased, for example, in sample 7, VMAX is 50.4
%, ΔV is 11.9% / Oe, the rate of impedance change is large, and a highly sensitive MI element can be obtained.

[0037]

As is apparent from the above description, according to the present invention, in the magnetic sensing element utilizing the magneto-impedance effect, good soft magnetic characteristics, high saturation magnetic flux density, and excellent corrosion resistance, The magnetic characteristics do not deteriorate under high temperature and high humidity conditions, the soft magnetic characteristics are maintained up to high temperature, the glass bonding can withstand the high temperature, and the magnetostriction is excellent. An excellent effect that a magnetic detection element with high sensitivity can be configured is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structure and dimensions of a sample of an MI device body according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a sample of an MI element in which the MI element body is fixed to a printed board.

FIG. 3 is an explanatory diagram showing how output characteristics of a sample of the same MI element are measured by an external magnetic field.

FIG. 4 is a graph showing a change in voltage across the MI element with respect to an external magnetic field.

FIG. 5 is a graph showing the characteristics of the voltage change with respect to the external magnetic field of each of the MI element and the MR element composed of magnetic thin films having different compositions.

[Explanation of symbols]

 1 Magnetic Thin Film 2 Ceramics Board 3 Printed Circuit Board 4 Solder 5 Helmholtz Coil 6 MI Element Sample 7 Driving Current Source

Claims (4)

[Claims] 1. A magnetic sensing element utilizing a magneto-impedance effect, wherein a, b, c, d, e, f represent the value of a composition ratio of atomic%,
Ml is at least one of Zr, Hf, Nb, Ta, Mo and W of elements, and MII is at least one of Ag and Cu of elements, and the composition is represented by a composition formula of Fea Alb MIc MIId Ce Of. , A, b, c, d, e, f are as follows: a + b + c + d + e + f = 100 0.5 ≦ b ≦ 20 2 ≦ c ≦ 25 0.05 ≦ d ≦ 5 0.5 ≦ e ≦ 250. A magnetic detection element comprising a magnetic thin film satisfying 2 ≦ f ≦ 6. 2. In a magnetic detection element utilizing the magneto-impedance effect, a, b, c, d, e, f and g represent the values of the composition ratio in atomic%, and MI represents the elements Zr, Hf, Nb, At least one of Ta, Mo, W, MII is at least one of the elements Ag and Cu, and L is at least one of rare earth elements, and the composition is represented by the composition formula Fea Alb MIc MIId Ce Of Lg. , A, b, c, d, e, f, and g are as follows: a + b + c + d + e + f + g = 100 0.5 ≦ b ≦ 20 2 ≦ c ≦ 25 0.05 ≦ d ≦ 5 0.5 ≦ e ≦ 25 A magnetic detection element comprising a magnetic thin film satisfying 0.2 ≦ f ≦ 6 0.1 ≦ g ≦ 5. 3. The magnetic thin film is provided with induced anisotropy so that a direction perpendicular to a direction in which a high frequency current is applied for magnetic detection is a direction of an easy axis of magnetization. The magnetic detection element according to claim 1 or 2, characterized in that. 4. The anisotropic magnitude Hk is 0.5 Oe-5.
The magnetic sensing element according to claim 3, wherein the magnetic sensing element is in the range of Oe.