JPS6011181A - Magnetic field sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention has a sensor surface formed of a groove-shaped thin layer having magnetic orientation and whose easy magnetization direction is a direction on the surface. The present invention relates to a magnetic field sensor and a position sensor using such an external magnetic field sensor.

[Technical background of the invention]

The Hall effect has traditionally been used to measure magnetic fields. When a current flows through a conductor and at the same time a magnetic field acts on the conductor perpendicular to the current, an electromotive force is generated perpendicular to the direction of both the current and the magnetic field, which can be extracted from the surface of the conductor as a voltage. . If this conductor exhibits magnetic anisotropy and its direction of easy magnetization coincides with the direction of the current, an additional emf is generated whose direction is in the plane determined by the magnetic field and the direction of the current. be.

This effect is called the "planar pole effect."

A magnetic field sensor that utilizes this effect is made of, for example, a disc-shaped thin metal plate that exhibits magnetic anisotropy, and the direction of easy magnetization is along the plane of the thin metal plate. This sensor has four terminals, equally spaced around its periphery, forming two current paths that intersect with each other, one in the easy magnetization direction of the magnetic anisotropy. It is also known to fabricate such magnetic field sensors using thin film technology (e.g. P
hys, 5tat, Sol, Vol. 26, p. 565,
D, Ky's paper rP1anar Hall FJff
ect inFerromagnetic Fi1ms
', 1968).

Such magnetic field sensors are very suitable for measuring weak, especially spatially restricted, magnetic fields. Its sensitivity is approximately proportional to the coercivity and therefore has a lower corner. Conventional sensors use metal alloys, preferably nickel, iron and cobalt alloys. The minimum coercive force that can be obtained with such alloys is about 100 mA/m.

The presence of a magnetic field not only causes a Hall voltage to be generated across a conductor, but also changes the electrical resistance of this conductor.

This effect can also be used to measure magnetic field strength. However, it can be seen from the table that when weak magnetic fields are measured in this way, the electrical resistance of the conductor is also influenced and perturbed by other factors, especially temperature changes.

[Summary of the invention]

An object of the present invention is to provide a magnetic field sensor that can measure even very weak magnetic fields.

According to the invention, the sensor surface (the thin film or layered sensor body is hereinafter referred to as sensor surface) is made of a ferromagnetic amorphous metal. Preferred embodiments thereof are described in claims 2 to 8.

The advantageous properties of the magnetic field sensor according to the invention enable a position detection device with very high resolution.

[Embodiments of the invention]

Embodiments will be described in detail below with reference to the accompanying drawings.

The sensitivity of a magnetic field sensor based on the planar Hall effect increases as the anisotropic magnetic field strength acting on it decreases.

The lowest possible anisotropic field strength is equal to the coercivity of the material.

Ferromagnetic amorphous metal has a coercive force of about 100 mA
Can be manufactured to be smaller than 7 cm. This value of approximately ]00 m)v- is the minimum achievable coercive force value in crystalline metal alloys. Amorphous metals are mainly produced in the form of thin strips (with a thickness of 100 μm), from which small disks are punched out, or in the form of thin layers (with a thickness of up to 5 μm).

This thin layer can be produced by vapor deposition or by coating.

Amorphous metals suitable for magnetic field sensors are alloys based on transition elements of the iron group. Amorphous metals are also B,
5i+- cents of 0 amorphous metals which may contain metalloids from the group consisting of C, Si, Ge, P and/or transition metals from the group consisting of Ti, Zr, )If, Nb. Other elements may be included up to (atomic fission). Especially suitable is Co-F
e-based alloy, preferably CozFeyBl On-
x-y, 70<x<80.4<:y<10 (where x
, y is an amorphous metal.

The easy magnetization direction in magnetic anisotropy can be obtained, for example, by tempering in a magnetic field.

The planar hole effect used in the present invention will be explained with reference to FIG. The figure shows a rectangular sensor surface, for example a thin film deposited on a metal foil member or substrate of thickness d XIl'1ili b and an optional but sufficient length (described below). An unchanging anisotropic magnetic field ■■ is applied to the sensor surface in the longitudinal direction. A current of current density J applied and extracted through the electrodes not shown flows through the electrodes not shown parallel to the anisotropic magnetic field. The external magnetic field H to be measured lies along the sensor surface in the direction perpendicular to the anisotropic magnetic field (k).The magnetization M is at an angle ψ from the direction of the anisotropic magnetic field Hk to the direction of the external magnetic field H. The direction of the anisotropic magnetization j%Hk is also called the "easy magnetization direction," and the direction perpendicular to it is called the "hard magnetization direction."The planar Hall effect is It generates a uniform, anisotropic magnetic field Hk and an electric field oriented perpendicular to the direction of the current of density j and in the sensor plane. If you take it out from the two electrodes, you will get a.

A current I having a current density j flows through two electrodes facing each other on the short sides located at both ends in the longitudinal direction. If these electrodes are present over the entire width of the short side, the Hall voltage will be at least partially shorted by these electrodes. Furthermore, if these current supply electrodes are not present over the entire width of the side, the current flowing across the sensor surface will not be uniform. Measurements are made by means of electrodes that measure the Hall voltage and by drawing some current from these electrodes for the purpose of measurement. If the geometry of the sensor surface and the electrodes attached to it are matched such that both the current density j and the electric field strength produced by the planar Hall effect are homogeneous in the region between the electrodes providing the Hall voltage. In that case, the sensor can be considered ideal.

In that case, (2) U,, =-, Z p −j Ib 0sln2ψUn
′++slnψ° Φ, , (3) Here, pii′
f is Lehnerhall constant.

Such a sensor surface, for example a thin layer that has been given a desired orientation (easily magnetized direction characterized by an applied anisotropic field) during fabrication or subsequent temperature treatment (anisotropic field) perpendicular to Ik When placed in an external magnetic field H lying in the plane of C/S, bsln2ψ (equation 2) then occurs between the electrodes. The voltage Un is also proportional to sin ψ, fish ψ, and 100 (equation 3). As is clear from these equations, UH increases as Hk decreases. That is, the sensitivity of the sensor increases as Hk decreases. The lower limit for Hlc is the holding force He. Approximately 100mA for crystalline metals
A coercive force smaller than /cm2 cannot be obtained. Significantly lower values can be obtained with ferromagnetic amorphous metals, especially alloys based on Co--Fe. Such amorphous metals are therefore particularly suitable for use in magnetic field sensors that utilize the planar Hall effect. An alloy that has proven particularly suitable for this purpose is C0XFeyB1oo
-knee 7, 70<x<, 80, 4<:y<10
(x, y are atomic %). Experiment with C7s
F e s B 2 o and C080B20 gave favorable results.

It is also possible to use other amorphous metals, which are alloys based on transition elements of the iron group. Such alloys may also include semimetals selected from the group consisting of B, C, Si, Ge, P, and/or Ti.

It may contain a transition metal selected from the group consisting of Zr, T(f, and Nb). It may also contain other elements up to 5 atoms (atomic atoms) of the amorphous metal.

An embodiment of the magnetic field sensor will be described below with reference to FIG. FIG. 2 shows a top view and a cross-sectional view of the sensor. Four electrodes 13 are attached to the top surface of the disc-shaped quartz substrate 11. The electrodes 13 are arranged in the outer region of the disk at radial intervals of 90 degrees. They are made of gold with an adhesive layer of chrome. A circular sensor surface 12 is deposited concentrically on the quartz substrate 11, partially overlapping the electrodes. That is C
The layer is made of 07sF85B2o and is formed by sputtering to a thickness of 100 to 500 nm. The diameter is about 5 to 20 thighs. This layer may also be formed by vapor deposition. The sensor surface 12 exhibits magnetic anisotropy, the direction of easy magnetization being parallel to a line connecting two opposing electrodes 13 on the sensor surface. This direction of easy magnetization is determined by hardening i'1 in a magnetic field. (350℃, 400℃
A/m for 30 minutes) is applied to the sensor surface. It is indicated as the anisotropic field strength Hk. The entire sensor surface 12 represents a single magnetic domain with magnetization parallel to the easy magnetization direction.

In principle, magnetic anisotropy can also be obtained already during the manufacturing process. That is, magnetic anisotropy can be obtained when the quartz substrate 1 is placed in a magnetic field during the footing or vapor deposition process. Instead of a thin layer, the sensor surface 12 may also be a flake made of the amorphous metal mentioned above.

The two electrodes of this magnetic field sensor, which are arranged opposite to each other in the direction of the anisotropic magnetic field Hk, are connected to a power supply supplying a mass flow I. When the sensor through which this current is flowing is placed in an external magnetic field H in the direction of difficult magnetization (perpendicular to the direction of easy magnetization), the magnetization M in the sensor surface 12 is between the mutually opposing electrodes in the direction of hard magnetization from the direction of easy magnetization. ni sinψ・iψ・
A Hall voltage compared to i is generated. Here d is the layer thickness of the sensor surface 12. Even when the external magnetic field is not pointing in the hard direction, the magnetization M is rotated by a precisely defined angle from the easy direction. Also in this case,
When the Hall voltage is generated L2, the magnitude and direction of the magnetic field can be accurately determined by the two magnetic field sensors even if the easy magnetization directions of the two magnetic field sensors are not perpendicular to each other. This allows both sensors to be constructed using a single substrate with appropriately distributed electrodes.

Instead of quartz, it is also possible to use glass, semiconductor materials or ceramic materials as the substrate.

Figure 3 shows a position sensor consisting of a magnetic field sensor (consisting of ?7, 32, 33), a permanent magnet 34 and two intermediate masks (consisting of 35.37 and 36.38, respectively). A cross-sectional view is shown. Each mask consists of a non-conductive, ferromagnetic but not yet ferrimagnetic support 35,36 and a soft magnetic layer 37,38 deposited thereon.

The two masks are movable relative to each other and the soft magnetic material layer has an aperture 39 (see Figure 4), which permanently positions the sensor depending on the relative position of the two masks as a whole. It is designed to shield from the magnetic field of the magnet or to allow a portion of the magnetic field to pass through to the sensor. Only one of the two masks is movable and indicates the position to be detected, while the position tag (at a distance in the direction of the other) is distributed such that the magnet is parallel to the sensor surface. At that time, the magnetic field lines of the permanent magnet are in a plane perpendicular to the sensor surface. When the shutter made up of two masks is opened, a part of the magnetic field lines reaches the sensor surface. The magnetic field sensor uses the magnetic anisotropic magnetic field Hk are oriented such that the easy magnetization direction of is perpendicular to these magnetic field lines (perpendicular to the plane of the paper in Figure 3).The Hall voltage UH is extracted by two electric currents, ?3. electrode 33 and permanent magnet 34 (2)
Jil's magnetic persimmon lies on a plane (plane of paper in the figure) approximately perpendicular to the sensor surface. The current ■ flows parallel to the anisotropic magnetic field Hk.

FIG. 4 shows a top view and a cross-sectional view of a portion of one of the two masks, which also consists of a support 35° and a soft magnetic layer 37, and has an opening of 0.39.

The other mask is of the same design.

FIG. 5 shows another embodiment of a position sensor having a magnetic field sensor using the Brehner-Hall effect. The magnetic field sensor l is arranged in a support 2 provided on one side of the mask 3. On the opposite side of the mask 3, a permanent magnet 4 is arranged facing the magnetic field sensor l. The axis passing through both magnetizations of the permanent magnet 4 is parallel to the mask 3. The mask 3 has a slit parallel to the axis of the permanent magnet 4. The magnetic field sensor I has a sensor surface on a plane perpendicular to the mask 3 and including the axis of the permanent magnet 4. The easy magnetization direction, characterized by the anisotropic field Hk, is perpendicular to the mask 3. Two electrodes are provided in the magnetic field sensor 1 such that the current ■ can flow parallel to the anisotropic magnetic field ■■ (one of these electrodes faces the mask 3, the other faces the opposite side) be). Two further electrodes are provided at the top and bottom of the sensor surface of the magnetic field sensor 1, from which the Hall voltage can be obtained. The magnetic field of the permanent magnet enters the magnetic field sensor 1 mainly through the slit 5 from its edge.

At that time, the Hall voltage is extracted from the upper and lower electrodes 6 as a signal 7, and when the mask 3 moves between the permanent magnet 4 and the magnetic field sensor 1, the magnitude of the signal 70 changes between the slit 5 and the intermediate metal strip bridge 8. changes according to the sequence of

6a to 6c are views of the apparatus of FIG. 5 from three directions. - Reference symbols N and S designate the magnetic poles of the permanent magnet 4; the other reference symbols correspond to those in FIG.

FIG. 7 shows the signal 7 obtained as the output of the magnetic field sensor 1 when the magnetic field sensor 1 moves parallel to the pattern of the mask 3 by a distance X and a steady magnetic field exists behind the mask 3.
shows the AC voltage component W of . A mask 3 in which the same output signal is transferred by the apparatus of FIGS. 5 and 6a to 6c.
It is obtained by

In the device of FIG. 5, the surface of the magnetic field sensor utilizing the planar pole effect is in the direction of the magnetic field lines. Instead of a two-dimensional sensor, a "linear" sensor is formed. Instead of a magnetic field sensitive surface there is a magnetic field sensitive line, by means of which the magnetic field is scanned in a direction perpendicular to the magnetic field and thus in a direction perpendicular to this line. If the magnetic field is modulated by a "magnetic grating" such as the mask 3, this modulation is caused by the edges of the thin layers of the sensor, i.e. by the particles parallel to the magnetic field lines.
Can be scanned with altitude or position accuracy.

Position sensors are primarily used to determine position or to measure the velocity or acceleration of mechanical parts in automatic equipment.

If the position of an object is to be observed, the changes in the magnetic field affected by this object can be used to determine the position of the object. If the object is not ferromagnetic, a magnetically transparent mask is assigned that extends between the magnet and the magnetic field sensor. Such devices are simple, robust and easily adapted to many applications. However, if small changes in motion are to be accurately recorded, the spatial size of conventional magnetic field sensitive sensors limits the resolution of such devices. In such cases, optical devices are usually used, in which one or two masks, for example provided with an open pattern or a grating, are moved between the radiation source and the radiation detector. When such gratings are optically scanned to accurately determine the position, velocity, or acceleration of a moving part, two demands conflict. That is, the sensitivity of the device depends on the resolution of motion (number of pulses/path length) and the brightness, and thus is determined, for example, by the diameter of the light beam. As the diameter of the light beam becomes smaller, the resolution increases.
The sensitivity obtained is reduced.

If the beam was too narrow, evaluation would obviously be impossible. If the beam is made thick enough for reliable evaluation, the resolution will be reduced. In optical scanning these constraints have been overcome by the use of fixed gratings and similar moving gratings.

In that case a beam of light can be used and a high resolution is nevertheless obtained. This is because the overall brightness depends on the relative positions of the two gratings. However, this creates a new requirement to place the two gratings very close to each other, which is often not possible due to mechanical tolerance problems. Furthermore, the higher the resolution of such optical position sensors, the more sensitive they become to contamination.

With the position sensor according to the invention, possible contamination is not a problem and both high resolution and high sensitivity are achieved.

In the case of the position sensor according to the invention, high resolution and high sensitivity go hand in hand. If, according to an embodiment of the invention, the sensor comprises a thin layer of amorphous metal, the edges of which are located parallel to the slits of the mask, and if a permanent magnet is arranged on the side opposite the layer of the mask, The magnetic field lines are also parallel to the slits, and the thinner the sensor, the higher its sensitivity and resolution, provided that the slits are penetrated with a strong enough magnetic field strength, and therefore the metal flakes bridging between the slits are saturated. . The total magnetic field strength acts behind the slit,
Behind the metal bridge there is a difference between the total magnetic field strength and the saturation field strength. These changes in magnetic field strength generate signals in the form of voltage changes, which can be amplified in an amplifier, evaluated in frequency and phase, or counted in a counter.

one edge of the thin amorphous metal layer faces the mask;
It is parallel to the slit and the metal a-tangle. The magnetic glands thus enter the edge of the lamina at the top, pass through the lamina and exit at its bottom, creating a voltage between the electrodes at the top and bottom edges as a result of the planar hole effect.

It is of course possible to use electromagnets instead of permanent magnets.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the planar hole effect, and the second
The figures are a top view and a sectional view of a magnetic field sensor according to an embodiment of the present invention. FIG. 3 is an Ur'Uii diagram of a position sensor according to an embodiment of the present invention, which includes a magnetic field sensor, a permanent magnet, and two relatively movable masks, and FIG. 4 shows the position of the position sensor shown in FIG. FIG. 3 is a top view and a cross-sectional view of a portion of a mask for a sensor. FIG. 5 is a perspective view of a position sensor according to an embodiment of the present invention, which includes a magnetic field sensor, a permanent magnet, and one mask;
6a, 6b, and 6c are views of the position sensor of FIG. 5 from three different directions, and FIG. 7 shows the waveform of a signal obtained by the position sensor of FIG. 5. DESCRIPTION OF SYMBOLS 1...Senna surface, 2...Support, 3...Mask, 4...Permanent magnet, 5...Slit, 11...Base, 12...Sensor surface, 13... Dentsu, 31...
・Substrate, 32...Sensor surface, 33...Electrode, 34
...Permanent magnet, 315.36...Support, 37, 3
8...Soft magnetic layer. Applicant's agent Patent attorney Takehiko SuzueFig, 7 Continuation of page 1 Priority claim @ June 28, 1983■ West Germany (DE)
■P3323197.4 @ Inventor Gerhardge Gasma Federal Republic of Germany 7300 Esgen Tomasetskabe 0 Inventor Siegzlied Müller Federal Republic of Germany 7440 Newgen Pfeifeltrasse 19 -42 ( ) -

Claims (1)

[Claims] (1) A sensor surface that exhibits magnetic anisotropy and has a plurality of conductive metal plates or thin layers whose direction of easy magnetization is on the sensor surface, and three or more terminals. A magnetic field sensor characterized in that the sensor surface is made of ferromagnetic amorphous metal. (2) The magnetic field sensor according to claim 1, wherein the amorphous metal is an alloy based on an iron group transition element. (3) Amorphous metal is B, C, St, Ge
, P. The magnetic field sensor according to claim 2, further comprising a metalloid selected from the group consisting of , P. (4) Amorphous metal is Ti, Zr, Hf
, Nb.
Magnetic field sensor described in section. (5) The magnetic field sensor according to any one of claims 2 to 4, characterized in that the amorphous metal contains another element in the 5-atomic trench. (6) The magnetic field sensor according to claim 2, wherein the amorphous metal is an alloy based on CO to Fe. (7) Amorphous metal is CoxFeyBl 0O−
x-y, where X is 7 when expressed in terms of atoms
Q < x < 80 and y is 4 y < 1
4. The magnetic field sensor according to claim 3, wherein the magnetic field sensor is 0. (8) The sensor surface is approximately circular or square, and 2
two terminals are attached to the periphery of the sensor surface such that the current flows through them and across the sensor surface approximately parallel to the direction of easy magnetization of the magnetic anisotropy, and two other terminals are attached to the sensor surface so that a straight line connecting them is The magnetic field sensor according to any one of claims 1 to 7, wherein the magnetic field sensor is attached to the periphery of the sensor surface so as to be perpendicular to the direction of easy magnetization of the magnetic anisotropy. (9) A sensor surface formed from a conductive thin metal plate or thin layer exhibiting magnetic anisotropy and whose easy magnetization direction is on the sensor surface, the outer sensor surface being made of a ferromagnetic amorphous metal, Three or more electrodes are attached,
A magnetic field sensor configured as a position detection device, characterized in that a permanent magnet is arranged near the sensor surface, and a movable mask is arranged between the magnetic field sensor and the permanent magnet. (1c) Claim 9, characterized in that the amorphous metal is an alloy based on an iron group transition element.
Magnetic field sensor described in section. 0η Amorphous metal is B, C, 81, Ge,
11. The magnetic field sensor of claim 10, further comprising a metalloid selected from the group consisting of P. (6) Amorphous metal is Ti, Zr, Hf
, Nb. The magnetic field sensor according to claim 10 or 11, characterized in that the magnetic field sensor contains a transition metal selected from the group consisting of , Nb. (1) Containing other elements at 5% (atomic %) of the amorphous metal (2)
The magnetic field sensor according to Items 0 to 12 or Item 1. 11. The magnetic field sensor according to claim 10, wherein the amorphous metal is a Co--Fe 4-based alloy. (One amorphous metal is CoxFeyBloo-x
-y There is Te, and X is 70 in terms of atoms.
12. The magnetic field sensor according to claim 11, wherein <X<80, and y satisfies 4<y<to. The αQ sensor surface is generally circular or square, and two terminals are attached around the periphery of the sensor surface such that current flows through those terminals and across the sensor surface approximately parallel to the easy magnetization direction of the magnetic anisotropy. , the other two terminals are attached around the sensor surface so that the straight line connecting them is perpendicular to the direction of easy magnetization of the magnetic anisotropy. The magnetic field sensor according to any one of Item 15. a'I) A plane containing both magnetic poles of the permanent magnet is perpendicular to the sensor surface, the direction of easy magnetization of the magnetic anisotropy of the sensor surface is perpendicular to the plane, and there is a space between the sensor surface and the permanent magnet. Relatively movable position-indicating masks are arranged essentially parallel to the sensor surface, the masks being configured to completely block the magnetic field or to pass a portion of the magnetic field, depending on their mutual position. A magnetic field sensor according to any one of claims 9 to 16, characterized in that: Oe, the sensor surface is on the plane containing two magnetic poles of the permanent magnet, the easy magnetization direction of the magnetic anisotropy of the sensor surface is perpendicular to the direction of the magnetic field lines of the permanent magnet, and the movable crying face indicating mask moves the magnetic field, Claims 9 to 16 are characterized in that the sensor has such a region and a region that does not block the magnetic field, and is disposed between the magnetic field sensor and the permanent magnet. magnetic field sensor.