JPH04242183A - Magnetism sensor - Google Patents

Abstract

PURPOSE:To provide a sensor sensing magnetism or a magnetism measuring element to measure the intensity of magnetism on the basis of a new principle. CONSTITUTION:By forming a piezoelectric film 16 and an electrode film 17 consisting of Ni, Al or the like on the base plate 11 constituted of a strong magnetic material, a piezoelectric vibrator is constituted. The characteristics of this piezoelectric vibrator such as resonance frequency, reverse resonance frequency, resonance resistance and reverse resonance resistance vary with the intensity of surrounding magnetic field. Therefor, by measuring these characteristics, the intensity of the magnetic field can be known.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to magnetic sensors, and more particularly to magnetic sensors that utilize a novel principle.

0002

[Prior Art] Conventionally, sensors that detect magnetism or
There are the following magnetic sensors such as magnetic measurement elements for measuring the strength of magnetism.

First, there are devices that utilize the magnetoresistive effect, and specific examples include Hall elements and SDMEs. This takes advantage of the fact that electrical resistance changes depending on the strength of the magnetic field.

[0004] Next, there are also devices that utilize the magnetostrictive effect. This category includes magnetostrictive sensors that utilize the fact that the magnitude of strain (displacement) in a solid changes depending on the strength of a magnetic field, and BSO sensors that utilize the fact that light is polarized by crystal strain.

Furthermore, there are proton magnetometers, fluxgate magnetometers, and the like.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic sensor constructed based on a new principle different from the conventional magnetic sensors described above.

[0007]

[Means for Solving the Problems] A magnetic sensor according to the present invention is characterized in that it includes a piezoelectric vibrator whose vibrating body is at least partially made of a ferromagnetic material.

[0008]

As described above, by using a ferromagnetic material as at least a part of the vibrating body, the characteristics such as the resonant frequency, anti-resonant frequency, resonant resistance, and anti-resonant resistance of the piezoelectric vibrator can be improved. It changes depending on the strength of the surrounding magnetic field. Therefore, by measuring any of these characteristics, the strength of the magnetic field can be determined.

Therefore, according to the magnetic sensor according to the present invention, it is possible to constitute a sensor for sensing magnetism or a magnetic measurement element for measuring the strength of magnetism, and it can be used as a substitute for the conventional Hall element, for example. It can be used as a product.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view showing a magnetic sensor 10 according to an embodiment of the present invention. FIG. 2 shows the line II-I in FIG.
It is a sectional view along I.

The magnetic sensor 10 includes a substrate 11 made of ferromagnetic material. In this embodiment, the substrate 11 is made of a ferromagnetic metal such as erinvar, and therefore has electrical conductivity. Two slits 12 and 13 are provided in the substrate 11. The area surrounded by these slits 12 and 13 is defined as a vibration area 14, and when the substrate 11 is supported around the periphery 15, vibrations in the vibration area 14 are not suppressed.

A piezoelectric thin film 16 made of a piezoelectric material such as ZnO is formed on the substrate 11 by, for example, sputtering. This piezoelectric thin film 16 extends from the vibration region 14 of the substrate 11 to a part of the periphery 15. An electrode film 17 made of Ni, Al, or the like is formed on the piezoelectric thin film 16.

[0013] In this way, a piezoelectric vibrator is constructed in the magnetic sensor 10. In FIG. 1, when a driving voltage is applied between one point on the electrode film 17 and one point on the substrate 11, such as points 18 and 19 indicated by "x" marks, the vibration region 14 It vibrates with a predetermined resonant frequency. At this time, by directly measuring the impedance between points 18 and 19, or by incorporating this magnetic sensor 10 into an oscillation circuit as an oscillator and measuring the resonant frequency, etc., it is possible to sense the magnetism, or to measure the strength of the magnetism. can be measured.

[0014] Below, an experimental example will be described in which changes in the impedance characteristics of the piezoelectric vibrator included in the magnetic sensor 10 caused by changing the magnetic flux density applied to the magnetic sensor 10 as shown in FIGS. 1 and 2 are investigated. do.

Probes were applied to points 18 and 19 in FIG. 1, respectively, to measure impedance. At this time, the magnet was brought close to each direction of ■, ■, ■, and ■ shown in FIG. 1, and the relationship between magnetic flux density and impedance characteristics was investigated. In addition, ■ is perpendicular to the paper surface and indicates the direction from the back to the front of the paper, ■ is perpendicular to the paper surface and indicates the direction from the front to the back of the paper, and ■ is , is parallel to the paper surface and indicates a direction to the left, and ■ is,
It is parallel to the page and points downward.

FIG. 3 shows the change in the resonant frequency due to the magnetic field, and FIG. 4 shows the change in the resonant resistance due to the magnetic field, obtained by the above measurements. 3 and 4, the horizontal axis represents the magnetic force (Gauss), and the vertical axis in FIG. 3 represents the rate of change in the resonance frequency (ppm
), and the vertical axis in FIG. 4 indicates the relative change value (Ω) of the resonance resistance.

As can be seen from these FIGS. 3 and 4,
The resonant frequency and resonant resistance change depending on the strength of the magnetic field applied to the magnetic sensor 10. Therefore, by measuring the resonance resistance or resonance frequency, the magnetic flux density can be determined.

In particular, as shown in FIG. 3, the resonance frequency is 1
Since the flux changes almost linearly up to about 500 Gauss, this magnetic sensor 10 can be used as a simple and highly accurate magnetometer.

Note that in the above-mentioned experimental example, the substrate 11
The length x width x thickness is 1.8 mm x 2.6 mm x 1.
A ZnO film with a thickness of about 20 μm was used as the piezoelectric thin film 16.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a magnetic sensor 10 according to an embodiment of the present invention.

FIG. 2 is a sectional view along line II-II in FIG. 1;

FIG. 3 is a diagram showing changes in the resonance frequency of the magnetic sensor 10 due to the magnetic field.

FIG. 4 is a diagram showing a change in resonance resistance due to a magnetic field of the magnetic sensor 10.

[Explanation of symbols]

10 Magnetic sensor 11 Substrate made of ferromagnetic material 16 Piezoelectric thin film 17 Ni electrode film

Claims (1)

[Claims] 1. A magnetic sensor comprising a piezoelectric vibrator in which at least a portion of the vibrating body is made of a ferromagnetic material.