JPS59104573A - Thin film magnetic sensor - Google Patents

Abstract

PURPOSE:To obtain steep, large induced pulse voltage that does not depend upon frequency for small external alternating magnetic field by forming two layers of cobalt-tantalum amorphous magnetic thin film of different coercive force. CONSTITUTION:A cobalt-tantalum amorphous magnetic thin film 6 having small coercive force is formed on a base plate 5 and a magnetic thin film 7 having large coercive force is successively formed by changing pressure of gaseous argon at the time of sputtering. Then, two thin films 6, 7 are etched with the mixed aq. solution of fluoric acid, nitric acid and water using photolithography to make them a strip form 8. The base plate 5 is cut into strip form and wound by a pickup coil 9. This thin film magnetic sensor is put in an alternating magnetic field to make the direction of the magnetic field and longitudinal direction of the thin film magnetic sensor parallel to each other, and an alternating magnetic field is impressed. When this alternating magnetic field becomes a certain strength, magnetization inversion of the magnetic layer having small coercive force takes place and induced pulse is generated in the coil 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a thin general magnetic sensor capable of detecting changes in external magnetic fields, particularly changes in minute magnetic fields.

Conventional configurations and problems There have been many magnetic sensors that use semiconductor materials, hk-based fruit, etc. that have been developed and put into practical use as magnetic sensors that detect the amount of change or unity of an external magnetic field. For example, devices using semiconductor materials include Hall elements, field effect transistor elements, and the like. These are InSb, GaAs, etc.
O-V group compounds, Si, Ge, etc. are mainly used.

Examples of magnetic materials used include memory, permalloy, sendust, Ni-Zn, and MHZll ferrite. Furthermore, in JP-A-51-187641, a magnetic wire is mechanically and thermally treated to change the coercive force of the layer near the surface of the magnetic wire (second magnetic part), and A magnetic device is described in which the coercive force is made larger than that of the magnetic part of the magnetic part) and the magnetic device is wound around the coercive force. This is because the coercive force of the second magnetic part is larger than the coercive force of the first magnetic part, and structurally, the inside of the magnetic wire consisting of the Fe-〇o-■ composition has a smaller coercive force. It is made up of thin wires where the part near the external surface has a large coercive force.

In this magnetic device, for example, when the direction and magnitude of the magnetic field at the throat are changed in the longitudinal direction of the thin wire, the part with a large coercive force interacts magnetically with the part with a small coercive force, so the magnetization direction of both are in the same direction and opposite to the external magnetic field, the magnetization reversal in the part with a small coercive force is the coercive force HC, which is larger, and the coercive force H in the part with a large coercive force.
This occurs with an external magnetic field smaller than c2. Also, if the external magnetic field and the magnetization direction of the part with high coercive force are the same, and only the magnetization direction of the part with low coercive force is opposite to them, the external magnetic field will gradually increase and the magnetization direction of the part with low coercive force will be the same. When the coercive force of the part with a small coercive force becomes similar to that of the magnetic field, the part with a large coercive force will help the G deformation reversal (reversal in the same direction as the magnetic field), and the part with a large coercive force will help, 11c + J ′
A! It occurs more sharply in the magnetic field of 30°C.

An electromagnetic induction phenomenon occurs due to magnetization reversal due to the expansion tube of the external field in the part with low coercive force, and an electric bit is generated in the pickup coil wound on a thin wire, and in the former case, a small pulse voltage is generated at both ends of the coil. In the latter case g3, a large pulse voltage can be obtained. The magnitude and steepness of this pulse voltage are far superior to those using magnetization reversal of a single magnetic material. In addition, in the case of a single magnet, the pulse width generated in the pickup coil is equal to the alternating wave number J of the external magnetic field.

On the other hand, in the case of the device described in JP-A-51-187641 FJ, it is induced by a large Barkhausen jump, and a steep pulse of a constant width is generated at the alternating frequency of an external magnetic field (R). As described above, the device described in JP-A-51-187641 has excellent characteristics, but its manufacturing method is complicated;
The yield is good (!! It is l1 to manufacture. Also l'■diameter 2
Although 50 micron fine wire is used, it is extremely difficult to create smaller devices. The magnitude of the external magnetic field to generate an even steeper induced pulse is approximately 1
This special 185 is suitable for magnetic heads that are as large as 5 Oersteds and need to obtain three pulses with a smaller external magnetic field, for example 1 Oersteds or less.
] The material described in JP-A-137641 is not used.

OBJECTS OF THE INVENTION The object of the present invention is to provide a magnetic sensor having a thin film structure that can significantly overcome the above-mentioned conventional problems and difficulties.
.

Structure of the Invention In order to achieve the above object, the thin film magnetic sensor of the present invention has the following features:
Cobalt-tantalum amorphous magnetic thin films whose main component is cobalt with different coercive forces are formed by stacking them on a two-layer substrate, and a pickup coil is provided on this.

DESCRIPTION OF EMBODIMENTS Hereinafter, practical examples of the present invention will be explained based on the C and I:"A sides. First, cobal l-(Co)-tantalum (Ta)
Using an alloy target, cobalt (C(1)-tantalum ('I') with different coercivity was deposited on the substrate by sputtering.
a) 2 JrFj magnetic thin films are stacked one on top of the other. The coercive forces of the two layers can be made different by changing the sputtering conditions, for example, the argon (Ar) gas pressure during sputtering. Magnetic NM made of cobalt ((0)-tantalum-CTa) is made amorphous by tantalum ('I'a).
This occurs when the amount of addition is 13a% or more. Even if the addition amount is 25at, it is still amorphous, but if the addition amount is 1%, the saturation magnetization of the T5 film is very small, about 10 Gauss, and is not suitable for the present invention. The appropriate range is 18at
% to 22at%. Figure 1 shows tantalum (1'a
) Changes in coercive force and saturation magnetization depending on the amount of addition (L) are shown.

@1 In the figure, (1) is a graph showing the change in coercive force, (2
) is a graph showing changes in saturation magnetization. Kobal)
(Co)-Tantalum ('l'a) - The retention force of amorphous 1 ~ 1 mo can be changed by using different targets of tantalum ('I'alffi), but the target must be changed for each V formation. Otherwise, it is necessary to change the target.Or, it is necessary to use a device that handles multiple targets, which causes difficulties in workability and equipment.In this point, argon (Ar) during sputtering
It is much easier and more appropriate to create magnetic films with different coercive forces by changing sputtering conditions such as gas pressure. Figure 2 shows how cobalt (
The changes in coercive force and saturation magnetization of Co)-tantalum CI"a) amorphous magnetism%h are shown. In the figure (
3) A graph showing the change in coercive force as l, and (4) shows the change in saturation magnetization f.

In this way, a cobalt (Co)-cuntal ('I'a) amorphous magnetic thin film with a small coercive force and the same magnetic iW Ikm with a large coercive force are successively stacked on a substrate to form C by simply changing the sputtering conditions. can.

In the present invention, two layers of cobalt (Co)-tantalum (I'a) with different magnetic forces are formed on a substrate because the magnetic R film has magnetostrictive properties.
First, cobalt (Co)-tantalum (-
1'a) - After forming an amorphous magnetic thin film, it is best to form a 1f magnetic thin film with a large coercive force on top of the amorphous magnetic thin film. When formed in this order, the coercive force of the magnetic thin film, which has a small required force, is stable, with little change due to the two-dimensional coercive force.
Cobalt (Co)-tantalum (1
'a)・Amorphous fJJ Ii! jQ (G)
Then, by changing the argon (A1) gas pressure during sputtering, a cobalt (('o)-tantalum (1'; θ) amorphous magnetic thin film (7) with a large coercive force is formed).

Next, as shown in Figure 4, the substrate (two layers of N FJ14 (0) (7) formed in layers) was etched with a mixture of hydrofluoric acid, nitric acid, and water using photolithography. 'U lll1 (8).

As shown in FIG. 5, the substrate (5) is cut into strips, and a pickup coil (9) is wound around the longitudinal direction of the strips to form a thin film magnetic sensor. The thin-film magnetic sensor thus produced is placed in an external alternating magnetic field having a single beam so that the direction of the magnetic field is parallel to the longitudinal direction of the thin-film magnetic sensor, and an alternating Nia field is applied.

When this alternating magnetic field reaches a certain strength, the magnetization of the magnetic layer with a small coercive force is reversed, and an induced pulse is generated in the coil (9). The direction of this magnetic field and the phenomenon of generation of induced pulses are the same as those in IJfJ No. 187641/1983. The height of this speech pulse TLii pressure differs depending on the coercive force (l) of the 2 Jm film formed by sputtering. According to the embodiment of the present invention, cobalt (Cn)-tantalum (Ta )・An induced pulse was obtained when the coercive force of the same magnetic thin film with a larger coercive force was 2 to 8 times the coercive force of the amorphous magnetic film. - When the ζ force is larger than 0.6 oersteds, the strength of the external alternating magnetic field generated by the induced pulse exceeds 1 oersteds when used as a thin film 1-minute sensor, and when used with a magnetic field smaller than 1 oersteds. The same sensor cannot be used when the cobalt (Co)-Ta amorphous magnetic in which has a coercive force smaller than 0.08 oersted is used.
was not obtained in the examples of the present invention. Cobalt (Co)-tantalum (T, ) amorphous magnetic f'E with a large coercive force If the coercive force of the thin film exceeds 8 times the coercive force of a residential thin film with a small coercive force, it becomes difficult to obtain an induced pulse voltage. .

The generation of the induced pulse voltage occurs because the magnetization reversal of the magnetic thin film with a small coercive force of the thin-film magnetic sensor is constrained to an appropriate coercive force of the magnetic thin film with a large coercive force due to changes in the applied external alternating magnetic field. If the constraint is too strong, that is, if the coercive force is too large, the two layers will magnetically behave as if they were a single J. I think that the. On the other hand, if it becomes smaller than twice, the interaction of 2B is too weak and the magnetization is reversed as a single magnetic thin film, so that the desired induced pulse Wi
Pressure cannot be obtained.

Next, specific embodiments of the present invention will be described. tantalum(
A 6-inch diameter target made of a cobalt (Co)-tantalum (Ta) alloy whose main component is cobalt (Co) to which 15 at% of ra) was added was used. The ultimate vacuum level is 2×1O
After setting the temperature to −7 Torr, argon (A
r) Cobalt (Co)-tantalum ('I) by changing the gas pressure
Sputtering 'a) to create amorphous magnetism with low coercive force? 'Jh was deposited on a glass substrate by 100 people.The sputtering power at this time was 400W.Next, the argon (Ar) gas pressure during sputtering was adjusted so that the coercive force was greater than that of the first layer of magnetic WHu. 1 under the condition of being t!I
A second amorphous magnetic thin film was formed on top of the second layer.

The sputtering power at this time was 400 Watts.

The thickness of the second layer was 8500A. Cobalt (Co)-tantalum (with different coercive forces) formed in two layers
Ta)・Amorphous magnetic thin film with a width of 500 μm and a length of 5
Add hydrofluoric acid: nitric acid: water - 5:1 to the strip (see Figure 4).
:94 (volume J21%) etching solution. Next, the substrate was cut into the same shape as the rectangular two-layer film. A steel wire having a diameter of 60 μm was wound around this in 50 turns to form a thin film magnetic sensor (see FIG. 6). A uniform external alternating magnetic field was applied to this sensor, and the induced pulse voltage generated in the coil was investigated. The following table shows the coercive force of the magnetic thin film of the present invention, the external alternating magnetic field necessary to generate the induced pulse, and the induced pulse voltage at that time. The induced pulse voltage value obtained was constant regardless of the frequency of the external alternating magnetic field.

Effects of the Invention As described above, the present invention involves forming an amorphous magnetic thin film of 2 to of cobalt (Co)-tantalum (1a) having different coercive forces on a substrate, and winding a pickup coil around the amorphous magnetic thin film. , is small, less than 1 oersted, and in response to the vibration, an induced pulse 7C pressure that is steep and large and does not depend on the frequency of the external alternating magnetic field is generated. In response to a minute magnetic field, like Jin, we can do 3 things: For example, 72.1 Kikii, I
(f+, “v” recorded in ml on the medium (11 Sumo JI
A sensor that can be used and is self-effective. Also iib
b, ・j
This has the advantage of producing an integrated sensor screen.

[Brief explanation of drawings]

The drawings show embodiments of the invention, and FIG.
Graph showing the liquefaction of power and saturation magnetization depending on the amount of addition of 'a).The second factor is argon (Ar) during sputtering.
) Graphs showing changes in coercive force and saturation magnetization due to gas pressure.
FIG. 1 is an explanatory diagram showing an order. (5)...Substrate, (6) (7-magnetic N film, (9)...
Coil Fig. 1 Ta 5 & IJrJ amount rate > Fig. 2

Claims (1)

[Scope of Claims] 1. A thin film magnetic sensor in which a cobalt-tantalum amorphous magnetic thin film whose main component is cobalt and has an easy coercive force is formed by stacking it on a two-layer substrate J2, and a pickup coil is provided on this. 2. The thin film magnetic sensor according to claim 1, wherein the cobalt-tantalum amorphous magnetic thin film has a tantalum content of 18 at% to 22 at*. 3. The thin film magnetic sensor according to claim 1, which is formed by forming a cobalt-tantalum amorphous magnetic fI film by sputtering. 4. Cobalt-tantalum with low coercive force is first placed on the substrate.
The thin film magnetic sensor according to claim 1, wherein an amorphous magnetic sublayer is formed, and a cobalt-tantalum amorphous magnetic thin film having a large coercive force is overlaid thereon. 2. The thin film magnetic sensor according to claim 1, wherein the magnetic thin film has a magnitude ratio of coercive force of 1:2 to 1:8. 6. Cobalt-tantalum amorphous magnetism with small lJ The coercive force value of all>j is 0.6 oe or more 1', 0
．． 086e or more, the thin film magnetic sensor according to claim 1.