JPH0295287A - Magnetoelectric converting element - Google Patents

Abstract

PURPOSE:To improve the sensitivity of the element by providing g narrow parts to main current paths as a sensing part on a straight line and reducing a saturated magnetic field. CONSTITUTION:Ferroelectric thin films 12 and 13 are formed on a glass substrate 11 first. Then the thin films 12 and 13 are patterned in continuous folded pattern on the straight line and the main current path parts 14 and 15 are formed by connecting wide parts 14a and 15a and narrow parts 14b and 15b. Then lead wires 33a, 33b and 35are connected to an output terminal 19 and current terminals 20 and 21, and a DC power source 31, a resistance 32 and a voltmeter 34 are connected to the lead wires 33a, 33b, and 35. This magnetic sensor can detect variation of an external magnetic field due to leak magnetic flux from a magnetic material layer by the anisotropic magnetic reluctance effect of the main current path parts 14 and 15 as sensing parts by arranging a rotary body etc., having the magnetic material layer whose surface is magnetized nearby the thin films 12 and 13. Consequently, the sensitivity of the element is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Field of Industrial Application) The present invention relates to a magnetoelectric transducer used in a magnetic sensor that detects the number of rotations, speed, rotation angle, etc. of a motor.

(Prior Art) As magnetic sensors that utilize the magnetoresistive effect, there are known those that utilize the Hall effect of semiconductors and those that utilize the anisotropic magnetoresistive effect of ferromagnetic materials.

This anisotropic magnetoresistance effect of a ferromagnetic material means that the electrical resistance of a thin film made of a high magnetic permeability material such as Co-old or Ve-NI causes a change in the current I flowing through the ferromagnetic material and the magnetization M of the ferromagnetic material. It is a direction-dependent phenomenon.

FIG. 4 shows an example of a magnetoelectric conversion element that utilizes the anisotropic magnetoresistive effect of such a ferromagnetic material.

In the magnetoelectric conversion element 1, a ferromagnetic thin film 3.4 having an anisotropic magnetoresistive effect is formed on the surface of a substrate 2 made of glass or the like. This ferromagnetic thin film 3.4 has a continuous folded pattern, and has a plurality of straight parts 3a24a serving as main current paths and a bent part 3b directly connecting these parts.
, 4b. Then, the ferromagnetic thin film 3
．． The straight portions 3 a s 4 a of 4 are arranged to be perpendicular to each other.

The ferromagnetic thin films 3 and 4 are connected at one end 3C14C, and an output terminal 5 is formed at this connection. Furthermore, current terminals 6.7 are formed at the other ends 3d, 4d of the ferromagnetic thin films 3 and 4.

A rotating body (not shown) having a magnetized magnetic layer on the outer periphery is arranged near the ferromagnetic thin film 3.4 of the magnetoelectric transducer 1, and a constant voltage is applied to the current terminal 5.6. A current (sense current) is applied to the ferromagnetic thin film 3.4, and changes in the sense current due to the anisotropic magnetoresistive effect are detected to detect the rotation speed, rotation angle, rotation speed, etc. of the rotating body. .

Here, the magnetization M of the ferromagnetic thin film depends on the component parallel to the film surface of the ferromagnetic thin film among the directional components of the external magnetic field, and the electrical resistivity ρ has an axis of symmetry in the direction of the magnetization M. , p −p upper 5in2θ+ρ//C082θ temple ρ knee Δ
ρeO32θ (where θ is the angle based on the direction of magnetization M, and ρ
± is the electrical resistivity at θ-90°, Δρ is the value obtained by subtracting the value of ρ from the resistivity ρ at θ-0''. The electrical resistance of the ferromagnetic thin film 3.4 decreases by receiving an external magnetic field perpendicular to the sense current flow direction and horizontal to the ferromagnetic thin film 3.4.This change in electrical resistance is expressed as a change in the sense current. By detecting and counting the number of changes,
As described above, movement of the rotating body can be detected.

By the way, the electrical resistance of this ferromagnetic thin film 3.4 does not change when the magnitude of the external magnetic field exceeds a certain value.

The strength of the external magnetic field at this time is called the saturation magnetic field. Therefore, by reducing this saturation magnetic field, it becomes possible to respond to a smaller external magnetic field, and the sensitivity of the magnetoelectric transducer can be improved.

This saturation magnetic field is expressed as the sum of an anisotropic magnetic field unique to the material and a demagnetizing field that depends on the shape of the material.

Now, considering the magnetoelectric conversion element shown in FIG. 4, the sensitivity of this element is almost determined by the anisotropic magnetic field of the material and the demagnetizing field of the main current path.

FIG. 5 is an enlarged view of the straight portion 3a and the bent portion 3b which serve as the main current path of the magnetoelectric transducer shown in FIG. Since the length C of the main current path is sufficiently larger than the width W of the main current path and the thickness t of the main current path, its demagnetizing field Hd can be obtained by the following equation.

Hd = 4πMs e t/w (In the formula, M s is the saturation magnetization of the ferromagnetic thin film.) Therefore, in order to improve the sensitivity of this magnetoelectric transducer, the width W of the main current path should be increased, and the width W of the main current path should be increased. It is necessary to reduce the thickness t of the current path.

However, since the width W of the main current path needs to be long within a predetermined area in order to obtain a predetermined electrical resistance, it is necessary to narrow the width W to ensure a sufficient current path. Furthermore, if the width W of the main current path is increased, power consumption will increase. Also, the thickness t of the ferromagnetic thin film is set at 50 to stabilize the film quality.
The lower limit is about 0 people. For this reason, there is a limit to the improvement in sensitivity in conventional magnetoelectric transducers.

(Problems to be Solved by the Invention) As described above, in order to improve the sensitivity of the magnetoelectric conversion element, it is necessary to reduce the demagnetizing field of the main current path formed by the ferromagnetic thin film. However, the width W of the main current path, which is a factor that determines this demagnetizing field, is limited by the required electrical resistance and power consumption, and the thickness t of the ferromagnetic thin film, which is another factor, is limited by the film formation conditions. Therefore, it has been difficult to improve the sensitivity beyond a certain level.

The present invention has been made to solve the problems of the prior art, and improves sensitivity by reducing the demagnetizing field that depends on the shape of the straight portion that becomes the main current path of the magnetoelectric conversion element, and reducing the saturation magnetic field. The object of the present invention is to provide a magnetoelectric transducer that has the following characteristics.

[Structure of the Invention] (Means for Solving the Problems) That is, the magnetoelectric transducer of the present invention has a plurality of ferromagnetic thin films having an anisotropic magnetoresistive effect formed on a substrate. The magnetoelectric transducer is configured with a main current path and a bent portion connecting these main current paths, and is characterized in that the main current path is provided with a constricted portion.

(Function) The magnitude Hd of the demagnetizing field in the main current path formed by the ferromagnetic thin film of the magnetoelectric conversion element is expressed by the following equation.

Hd −N M s ・・・・・・
...(1) Here, N is the demagnetizing field coefficient. The demagnetizing field coefficient in the linear direction within the plane where the element is located is N1, the demagnetizing field coefficient in the direction perpendicular to this linear direction and within the plane is N2,
If the demagnetizing field coefficient in the direction perpendicular to the element surface is N3, the relationship shown in the following equation is established.

N, +N2 +N3-4π ・・・・・・(II
) In the magnetoelectric transducer of the present invention, N1 is increased by providing a constriction in the main current path serving as the sensing portion in a direction perpendicular to the current flow direction within the same plane. N3 hardly changes depending on the presence or absence of constriction. Therefore, based on the relationship expressed by equation (II) above, N2 becomes smaller.

Here, the sensitivity of the magnetoelectric transducer that forms the linear sensing section strongly depends on N2, and therefore, the sensitivity can be improved by reducing N2.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a magnetic sensor using an example of a magnetoelectric conversion element according to the present invention.

As shown in the figure, the magnetoelectric transducer 10 has a ferromagnetic thin film 12.13 such as Co-Ni or Pc-Ni having an anisotropic magnetoresistive effect formed on a substrate 11 made of glass or the like. There is. This ferromagnetic thin film 12.13 has a continuous folded pattern shape and is composed of a plurality of main current path sections 14.15 serving as sensing sections and a bent section 16.17 directly connecting these sections. These main current path portions 14 and 15 are linear current paths in the longitudinal direction, and the main current path portion 14 of the ferromagnetic thin film 12 and the main current path portion 15 of the ferromagnetic thin film 13 are 71S are arranged so that the flow directions are perpendicular to each other.

These main current path portions 14.15 each have a shape in which a plurality of rectangular cutouts 18 are provided on both sides of a straight portion, that is, a linear wide portion 14.
1.5a is connected by constricted portions 14b and 15b to form a current path. Further, the main current path portions 14 and 15 are connected by their negative ends 14c and 15C, and an output terminal 19 is formed at the connection portion. Further, current terminals 20.21 are formed at the other end portions 14d and 15d of the main current passage portion 14.15, respectively.

A DC power supply 31 for supplying a sense current and a resistor 32 connected in series to the DC power supply 31 are connected to the current terminals 20.21 of the magnetoelectric conversion element 10 via lead wires 33a and 33b. At the same time, a voltmeter 34 is connected via a lead wire 35 between the output terminal 19 and the lead wire 33a in order to detect changes in the sense current due to the anisotropic magnetoresistive effect of the ferromagnetic thin film 12.13. A magnetic sensor is constructed by connecting them.

Such a magnetic sensor is manufactured, for example, as follows.

That is, first, a ferromagnetic thin film 12. is deposited on a glass substrate 11.
13 is deposited on about 500 people by vacuum evaporation, sputtering, or the like. Next, the ferromagnetic thin films 12 and 13 are patterned into a linear continuous folding pattern using photolithography, etc., and the main current path portion 1
By forming a plurality of notches 18 in each of 4.15, the main current passage portion 14.15 is formed into a wide portion 14a.
115a is connected by constricted portions 14b and 15b.

After that, connect the lead wires 33a, 33b, 3 to one output terminal and the current terminal 20.21 with indium solder, etc.
5, and a DC power supply 31, a resistor 32, and a voltmeter 34 are connected to these lead wires 33a, 33b, and 35.

In the magnetic sensor of this embodiment, by arranging a rotating body or the like having a magnetic layer whose surface is ferromagnetic near the ferromagnetic thin film 12, 13, an external Changes in the magnetic field can be detected as changes in the sense current due to the anisotropic magnetoresistive effect of the main current path section 14.15, which is the sensing section.

The magnetoelectric conversion element 10 in the magnetic sensor of the above embodiment is as follows:
Since the demagnetizing field coefficient N1 in the current flow direction of the main current path portion 14.15 is increased by the constrictions 14b and 15b formed by the notches 18 provided perpendicularly to the current flow direction, The demagnetizing field coefficient N2 in the direction perpendicular to the current flow direction in the same plane, which influences the sensitivity of the magnetoelectric conversion element 10, decreases. As a result, the sensitivity is significantly improved compared to conventional magnetoelectric transducers in which the main current path is linear.

Note that the shape of the main current path is not limited to the shape shown in the above embodiment, but a constriction is provided in the direction perpendicular to the current flow direction, and the shape of the main current path is narrowed in the direction of current flow. Any shape may be used as long as it is possible to increase the demagnetizing field coefficient N1, such as a shape in which circular portions 41 are connected by a constriction 42 as shown in FIG. Various shapes can be used, such as a shape in which arc-shaped notches 44 are provided on both sides of a straight portion 43 as shown in FIG. Further, the area, number, etc. of the constricted portions are appropriately selected according to the conditions of use.

[Effects of the Invention] As explained above, in the magnetoelectric transducer of the present invention, by providing the constricted portion in the main current path that serves as a linear sensing portion, the demagnetizing field of this main current path is caused by a straight line. Small compared to the shape. Therefore, according to the present invention, it is possible to obtain a magnetoelectric transducer with improved sensitivity compared to conventional magnetoelectric transducers.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a magnetic sensor using a magnetoelectric transducer according to an embodiment of the present invention, and FIGS. 2 and 3 are plan views showing a modification of the main current path section of the magnetoelectric transducer shown in FIG. 1. Figure, 4th
This figure is a plan view showing a magnetic sensor using a conventional magnetoelectric conversion element, and FIG. 5 is an enlarged view of the main part of FIG. 4. 10... Magnetoelectric conversion element, 11... Substrate, 12.13
...Ferromagnetic thin film, 14.15... Main current path section,
14b, 15b... Constricted portion, 16.17... Bent portion. Applicant Toshiba Corporation Agent Patent Attorney Suyama Sa - 1 Father-in-law 1F! I Denika,

Claims (1)

[Claims] A ferromagnetic thin film having an anisotropic magnetoresistive effect formed on a substrate constitutes a plurality of main current paths serving as a sensing portion and a bent portion connecting these main current paths. A magnetoelectric conversion element, characterized in that the main current path is provided with a constricted part.