JP2642268B2 - Magnetic field strength measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element used for a magnetic sensor and the like and a method for measuring a magnetic field intensity.

[0002]

2. Description of the Related Art Hitherto, as a magnetoresistive element, an element utilizing a magnetoresistance effect of a ferromagnetic material has been widely used.
FIG. 3 shows an example of a conventional magnetoresistive element. The magnetoresistive element includes a magnetoresistive element portion 11 made of a ferromagnetic material and a pair of electrode portions 12 at both ends thereof. The magnetoresistance effect is a phenomenon in which the resistance R of a ferromagnetic material changes as R = R ₀ + ΔR · cos ² θ depending on the angle θ between the direction of magnetization of the ferromagnetic material and the direction of current flowing through the ferromagnetic material. Here, R ₀ is the resistance when the magnetization direction is perpendicular to the current direction, and ΔR is the difference between the resistance when the magnetization direction and the current direction are parallel and R ₀ . The S / N ratio of the magnetoresistive element is represented by ΔR / R ₀ . FIG. 4 shows N, which is a ferromagnetic material conventionally used in a magnetoresistive element.
4 shows the magnetic field dependence of resistivity in an iFe alloy. R ₀ ,
When the resistivity corresponding to ΔR is ρ ₀ and Δρ, respectively,
ΔR / R ₀ = Δρ / ρ ₀ is (20.8−20) / 20 =
0.04. Other ferromagnetic materials, NiCo, N
Δρ / ρ ₀ is about several percent at room temperature even in iCu alloys and the like, and the S / N ratio was insufficient for use in magnetic field sensors and the like. As described above, the magnetoresistive element utilizing the magnetoresistance effect of the ferromagnetic material has a problem that the S / N ratio is extremely low.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetoresistive element having a high S / N ratio by solving the low S / N ratio which has been a problem of the conventional magnetoresistive element. An object of the present invention is to provide a method for measuring a magnetic field intensity using the magnetoresistive element.

[0004]

In order to achieve the above object, a method for measuring a magnetic field strength according to the present invention provides a magnetic resistance element having a soft magnetic film provided on both surfaces of a nonmagnetic conductor film in a magnetic field. And applying high frequency to both sides of the non-magnetic conductor film of the magnetoresistive element, and measuring the intensity of the magnetic field based on a change in the high frequency resistance value of the magnetoresistive element due to the magnetic field. It is characterized by having.

[0005]

[0006]

[0007]

The present invention makes use of the fact that the high frequency resistance of the magnetoresistive element has a large magnetic field dependence. As a result, the magnetic field can be measured at a high S / N ratio.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention, in which a soft magnetic body 1 is provided above and below a line composed of a conductor 2 having a pair of electrodes 4. Reference numeral 3 denotes a magnetoresistive element, and reference numeral 5 denotes an external magnetic field. The resistance R when the frequency f at both ends of the element having such a structure is applied.
(F) is represented by R (f) = R ₀ (f) + ΔR _mag (f). Here, R ₀ (f) is the resistance in the case where only the conductor without the soft magnetic material is laminated, and ΔR _mag (f) is the increase in resistance due to the provision of the soft magnetic material. R ₀
(F) has a constant value almost independent of the frequency when the frequency is 1 GHz or less. On the other hand, in a soft magnetic material, the imaginary part μ ″ (f) of the relative magnetic permeability increases in a high frequency range, and ΔR _mag (f) increases due to the relationship ΔR _mag (f) ∝f · μ ″ (f). . When an external magnetic field is applied to the soft magnetic material, μ ″ (f) gradually decreases, and finally when the magnitude of the applied magnetic field becomes sufficiently large as compared with the anisotropic magnetic field of the soft magnetic material, μ ″ (f) f) becomes zero.
Therefore, the S / N ratio of the magnetoresistive element shown in FIG. 1 is represented by ΔR _mag (f) / R ₀ (f). R ₀ (f) is small and ΔR _mag
Since (f) has a very large value in a high frequency range, this magnetoresistive element has a very large S / N ratio.

FIG. 2 shows the external magnetic field dependence of the resistance measured at a frequency of 500 MHz using a 1 μm-thick Cu as the conductor 2 and a 0.5 μm-thick NiFe alloy as the soft magnetic material 1. The length of the magnetoresistive element is 8 mm and the width is 1.5 mm. Resistance value is 4.70Ω when external magnetic field is zero
However, it decreases sharply with the increase of the external magnetic field, and NiF
Under an external magnetic field sufficiently larger than the anisotropic magnetic field 5 Oe of the e-alloy, the value drops to 0.695Ω. In this experiment, R
₀ = 0.695Ω, ΔR _mag = 4.70-0.695 °
4.0 and the S / N ratio is ΔR _mag / R ₀ ≒ 4.0 /
This is a very high value of 0.695 ≒ 5.76.

In the magnetoresistive element according to the present invention, C
By increasing the thickness of the u and NiFe alloys, R
_{Since 0} can be decreased and ΔR _mag can be increased, it is possible to further improve the S / N ratio by appropriately setting these film thicknesses.

As is apparent from the results, the magnetoresistive element of the present invention has an advantage that the S / N ratio is higher than that of the conventional magnetoresistive element.

As shown in FIG. 2, when a high frequency is applied to both ends of the magnetoresistive element, the resistance value largely depends on the external magnetic field. Therefore, if the calibration curve is obtained in advance, the intensity of the external magnetic field can be obtained from the resistance value.

In FIG. 1, the soft magnetic material 1 is composed of a conductor 2
As another example, a magnetoresistive element in which a soft magnetic material is provided on a conductor surface through a non-magnetic material as in the case of FIG. / N
It functions as a magnetoresistive element having a ratio.

[0015]

As described above, the magnetoresistive element according to the present invention has an advantage that the S / N ratio as the magnetoresistive element is very high because the high-frequency resistance shows a large magnetic field dependence.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a magnetoresistive element of the present invention.

FIG. 2 is a characteristic diagram showing an example of magnetic field dependence of resistance in the magnetoresistive element of the present invention.

FIG. 3 is a perspective view showing a conventional magnetoresistive element.

FIG. 4 shows NiFe used in a conventional magnetoresistive element.
FIG. 4 is a characteristic diagram showing the magnetic field dependence of resistivity in a film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Soft magnetic body 2 Conductor 3 Magnetoresistive element part 4 Electrode 5 External magnetic field

Claims (1)

(57) [Claims] 1. A step of disposing a magnetoresistive element having soft magnetic films provided on both sides of a nonmagnetic conductor film in a magnetic field, and a step of applying a high frequency to both sides of the nonmagnetic conductor film of the magnetoresistive element. And measuring the strength of the magnetic field based on a change in the high-frequency resistance value of the magnetoresistive element due to the magnetic field.