JPH0426227B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Application) The present invention relates to a ferromagnetic magnetoresistive alloy film, and is particularly applicable to a thin film strip shape for use in magnetic sensor elements, magnetic head elements, magnetic bubble detection elements, etc. The present invention relates to a ferromagnetic magnetoresistive alloy film to be provided. More specifically, the present invention relates to ferromagnetic magnetoresistive alloy films having high magnetic field sensitivity in the form of thin film strips.

(Background) In recent years, magnetic sensors and magnetoresistive thin film magnetic heads that use ferromagnetic magnetoresistive alloy films to detect the rotation angle and rotational speed of an object, and the use of the ferromagnetic magnetoresistive alloy films have been developed. The development of magnetic bubble detection elements, etc., is progressing rapidly.

FIG. 1 shows a schematic structure of a magnetic sensor that detects rotation angle and rotation speed.

A detecting section 22 having a magnetic recording medium 20 on its circumferential surface is fixed to a rotating shaft 21, that is, a rotating shaft 21 of a rotating body (not shown) that is a subject. The magnetic recording medium 20 is circumferentially magnetized 25 at a predetermined recording wavelength by a magnetic head (not shown).

On the other hand, a substrate 30 is disposed adjacent to the surface of the magnetic recording medium 20, and a strip-shaped ferromagnetic magnetoresistive alloy film 1 is deposited on the surface thereof facing the magnetic recording medium 20. , sputtering, or other methods.

As described above, since the ferromagnetic magnetoresistive alloy film 1 formed on the substrate 30 receives the magnetic field from the magnetized pattern of the magnetic recording medium 20, the electrical resistance changes as the shaft 21 rotates. do. Based on this, the rotation angle and rotation speed of the rotating body can be detected by performing well-known calculations.

FIG. 2 is a schematic perspective view showing an example of a magnetoresistive thin film magnetic head.

A permanent magnet film 31 for applying a bias magnetic field is formed on the substrate 30, and a non-magnetic insulating film 3 is formed on the upper surface of the permanent magnet film 31 for applying a bias magnetic field.
2, a strip-shaped ferromagnetic magnetoresistive alloy film 1 is formed. Lead wires 33 are connected to both ends of the ferromagnetic magnetoresistive alloy film 1 .

In FIG. 2, the electrical resistance of the ferromagnetic magnetoresistive alloy film 1 changes due to the influence of a magnetic field 2 generated from a recording medium (not shown). Therefore, the current flowing through the alloy film 1 or the lead wires 33, 33
Information can be reproduced based on the potential difference between the two.

In this case, the permanent magnet film 31 is magnetized 40 in the same direction as the magnetic field 2 generated from the recording medium, and functions to apply a bias magnetic field to the ferromagnetic magnetoresistive alloy film 1.

As mentioned above, 82
Permalloy, which is a wt%Ni-18wt%Fe alloy,
It has been widely used for a long time.

In addition, in the above-mentioned magnetic sensors, magnetoresistive thin film magnetic heads, magnetic bubble detection elements, etc., the film thickness is 25 to 400 nm and the width is 20 to 30 μm.
Generally, a strip-shaped ferromagnetic magnetoresistive film is used.

The ferromagnetic magnetoresistive effect ΔR/R of a permalloy film with a thickness of 30 to 40 nm is approximately 2.5%, and the ΔR/R of a permalloy film with a thickness of 300 to 400 nm is approximately 3.5.
%.

"IEEE Transactions on Magnetics"
(MAG-11, No. 4, July 1975 issue No. 1018-1038
Page) contains 92%Ni-8%Fe, 92%Ni-8%Fe, and
(70-90)%Ni-(30-10)%Co, 67%Ni-30%
It is described that there is Co-3% Cr.

"Thin Solid Films" (Vol. 48, 1978, No. 247)
(page 255) contains a ternary alloy of 72 wt% Ni-18
wt%Fe-10wt%Co, 64wt%Ni-17wt%
Fe - 19 wt% Co and 60 wt% Ni - 11 wt% Fe
-29 wt% Co is disclosed, and it is stated that these have a greater ferromagnetic magnetoresistive effect than permalloy films.

Furthermore, “IEEE Transactions on Magnetics”
(MAG-19, No. 2, March 1983 issue, pages 104-110)
Also, 65%Ni−15%Fe−20%Co and 60%Ni−
10%Fe-30%Co is disclosed, and it is stated that these ternary alloys also have a larger ferromagnetic magnetoresistive effect than permalloy films.

The positions of these known magnetic alloy films, which have a larger ferromagnetic magnetoresistance effect than the permalloy film, in the Ni-Fe-Co ternary diagram are indicated by circles in FIG. However, these magnetic ternary alloy films have the following drawbacks.

Generally, the magnetoresistive alloy film of a magnetic sensor element and a magnetoresistive thin film magnetic head element is used in the form of a thin film strip, as can be easily understood from FIGS. 1 and 2 and the description thereof. At this time, as shown in FIG. 2, the magnetic field 2 is applied in the plane of the thin film in its width direction, that is, at right angles to its length direction.

FIG. 3 is a perspective view schematically showing this state. In this case, the dimensions of each part are typically the film thickness d
is 20~50nm, width W is 5~40μm, length L is 100~
It is 3000μm. That is, in this magnetoresistive alloy thin film, the length L is sufficiently larger than its width W, and the width W is sufficiently larger than its film thickness d.

By the way, the magnetoresistive alloy films shown in FIGS. 1 to 3 require not only a large ferromagnetic magnetoresistive effect, but also the following two points.

First, it must have good magnetic field sensitivity - that is, it must exhibit a sufficient ferromagnetic magnetoresistive effect even if the applied magnetic field 2 is small.

The second requirement is that the hysteresis phenomenon with respect to the magnetic field 2 is small; that is, the magnetic film must have uniaxial magnetic anisotropy, with the direction of length L being the axis of easy magnetization.

The first magnetic field sensitivity will be further explained. Generally, it is considered best to use the apparent anisotropic magnetic field H'k as a parameter representing magnetic field sensitivity.

The apparent anisotropic magnetic field H'k means that when a magnetic field 2 is applied in the width direction of the thin strip-shaped magnetoresistive alloy film 1 shown in FIG. 3, the magnetoresistive effect as shown in FIG. This is a magnetic field that can be considered to be practically saturated (even if the applied magnetic field H changes, the resistance value R no longer changes).

The magnetoresistive alloy film of the magnetoresistive thin film magnetic head is generally used by applying a bias magnetic field in a direction forming an angle of about 45 degrees with respect to the direction of the length L. In this case, as for the magnetic field sensitivity of a single magnetoresistive alloy film, it is common to evaluate the characteristics of the magnetic film using the above-mentioned apparent anisotropic magnetic field H'k.

Regarding magnetic bubble detection elements, "IEEE
"Transactions on Magnetics" (MAG-19, No.
2, March 1983, pp. 104-110, the characteristics are evaluated using the apparent anisotropic magnetic field H'k.

The apparent anisotropic magnetic field H'k of the magnetoresistive alloy film in the shape shown in FIG. 3 is given by the following equation (1).

H′k=aHk+bd/WBs...(1) In equation (1), Hk is the true anisotropic magnetic field, Bs is the saturation magnetic flux density, and a and b are constants that are not related to the characteristics of the magnetic film. Therefore, in the above equation (1), what is related to the magnetic film itself is the true anisotropic magnetic field Hk and the saturation magnetic flux density Bs.

By the way, a magnetic film with good magnetic field sensitivity means that the apparent anisotropic magnetic field H'k is small. As is clear from equation (1) above, this means that the true anisotropic magnetic field Hk is small and the saturation magnetic flux density Bs is small.

It is a known material disclosed in each of the above publications.
All Ni-Fe-Co alloy films have a saturation magnetic flux density Bs
is large, and therefore the apparent anisotropic magnetic field H'k is large.

Furthermore, 92%Ni-8%Fe, (70~90)%Ni-(30
~10)%Co and 67%Ni-30%Co-3%Cr have the disadvantage that it is difficult to obtain a film with uniaxial magnetic anisotropy.

(Objective of the Invention) The present invention has been made to eliminate the above-mentioned drawbacks, and its purpose is to improve the permalloy film, which is an 82% Ni-18% Fe alloy, and the known Ni-Fe-
Compared to Co ternary alloy films, the ferromagnetic magnetoresistive effect is larger in the thin film strip shape, and the saturation magnetic flux density Bs is smaller than known materials (i.e.,
An object of the present invention is to provide a good ferromagnetic magnetoresistive alloy film that has a small apparent anisotropic magnetic field and exhibits uniaxial magnetic anisotropy.

(Summary of the invention) The present invention provides a Ni-Fe-Co ternary alloy film that includes:
When the weight composition is expressed as Ni _lxy −Fe _x −Co _y , by setting the following two inequalities 0.05≦x 0.15≦y≦0.5−2.5x to a composition range that satisfies the above x and y. , Ni-Fe- which has a larger ferromagnetic magnetoresistance effect than permalloy film and has a known saturation magnetic flux density.
The present invention is characterized in that it is possible to realize a thin strip-shaped ferromagnetic magnetoresistive alloy film that is smaller than a Co ternary alloy film and exhibits uniaxial magnetic anisotropy.

(Example of the Invention) The present inventors determined the composition range of the Ni-Fe-Co ternary alloy in order to obtain a thin strip-shaped ferromagnetic magnetoresistive alloy film having excellent properties as described above. In order to do so, the ternary alloy films having various compositions were experimentally prepared.

Then, the ferromagnetic magnetoresistive effect ΔR/R (%), the saturation magnetic flux density T (relative value when permalloy is set to 1), and whether or not they exhibited uniaxial magnetic anisotropy were measured for each of these. The results are shown in Table 1 (last page).

In addition, in these experiments, each sample
The Ni-Fe-Co alloy film corresponding to No. was obtained by vapor deposition from one vapor deposition source having a predetermined composition. Although resistance heating was used as the heating source for vapor deposition, electron beam heating can be used in exactly the same way.

In addition, the vacuum pressure during vapor deposition is preferably 5×10 ^-6 Torr or less, and furthermore, in order to obtain an alloy film with little variation and a large ferromagnetic magnetoresistance effect, 1×
It was found that 10 ^-6 Torr or less is desirable.

The substrate temperature during vapor deposition is generally kept in the range of 200 to 400°C, and it has been found that approximately 350°C is desirable in order to obtain an alloy film with little variation and a large ferromagnetic magnetoresistive effect. Ivy.

As the substrate in this case, glass, ceramics, or the like having a sufficiently flat surface can be used. The deposition rate may be in the range of 1 to 3 nm/S, and it was confirmed that the deposition rate does not have a large effect on the ferromagnetic magnetoresistive effect.

Methods for imparting uniaxial magnetic anisotropy include a method of vapor deposition in a direct current or alternating current magnetic field in a fixed direction, an oblique vapor deposition method in which the deposited particles are tilted from the normal direction of the substrate surface,
A method of oblique evaporation and rotating the substrate, a method of evaporation in a rotating magnetic field, etc. can be used. The simplest method for imparting uniaxial magnetic anisotropy is to deposit in a direct current magnetic field.

The film thickness varies depending on the application, but is 20~
It is easy to vary within a range of 400 nm.

Table 1 shows the film thickness of 45 to 50 nm formed by vapor deposition method.
The ferromagnetic magnetoresistive effect, saturation magnetic flux density, and uniaxial magnetic anisotropy of ternary alloys of Ni _lxy -F _x -Co _y with various compositions were measured.

In the Ni _lxy −Fe _x −Co _y alloy film, generally,
It is known that increasing the Co content increases the ferromagnetic magnetoresistive effect, but from the experimental results in Table 1, in order to show a substantially larger ferromagnetic magnetoresistive effect than the permalloy film, The composition ratio of Co
It can be seen that it is necessary to set the content to 15% by weight or more.

That is, y needs to be 0.15 or more. In the Ni-Fe-Co3 component diagram shown in FIG. 5, this corresponds to the diagonally shaded region on the Co side of the straight line 11 in the diagram.

Next, from Table 1, Ni _lxy −Fe _x −
It can be seen that in order to obtain a uniaxial magnetic anisotropy film in a _Coy alloy film, it is necessary to set the composition ratio of Fe to 5% by weight or more. That is, x needs to be 0.05 or more, and this is the shaded area on the Fe side of the straight line 12 in FIG.

Further, in the Ni _lxy -F _x -Co _y alloy film, the composition range in which the saturation magnetic flux density is smaller than that of the above-mentioned known Ni-Fe-Co alloy film is such that y is 0.15 or more and x
It is determined from Table 1 that in a composition range that satisfies the two conditions that y is 0.05 or more, y is in a range of (0.5-2.5x) or less. This area is the fifth
This is the diagonally shaded area on the Ni side of the straight line 13 in the figure.

Taking the above into account, it is clear that the ferromagnetic magnetoresistive effect characteristics that meet the purpose of the present invention are as follows: (1) the ferromagnetic magnetoresistive effect is larger than that of the permalloy film, and (2) the uniaxial magnetic anisotropy is _{In FIG .} Book straight line 11,1
It is represented by an area surrounded by 2 and 13.

Furthermore, according to the experiments conducted by the present inventors, the film thickness of Ni _0.71 −Fe _0.09 −Co _0.20 within the above composition range
The ferromagnetic magnetoresistive effect of the 350 nm sample was 48%, which was confirmed to be larger than the 3.5% value of the ferromagnetic magnetoresistive effect of permalloy of the same thickness.

Note that the method for forming the alloy film of the present invention is not limited to the vacuum deposition method, and it goes without saying that a sputtering method is also effective.

(Effects of the Invention) As is clear from the above description, the ferromagnetic magnetoresistive alloy film having the composition range limited by the present invention can be produced in the same thin film strip shape as conventionally used in practical use. Compared to the same type of alloy known as Permalloyre, which is used for this purpose, it has the effect of having a large ferromagnetic magnetoresistance effect, a saturation magnetic flux density that is so small that it does not pose a practical problem, and a uniaxial magnetic anisotropy. It is extremely suitable for use in magnetic sensors, magnetoresistive thin film magnetic heads, magnetic bubble detection elements, and the like.

The Ni-Fe-Co alloy film of the present invention also has the advantage that its constituent elements are Ni, Fe, and Co, which have relatively similar vapor pressures, and can be obtained industrially with good reproducibility. have.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the schematic structure of a resistive thin film magnetic sensor for detecting rotation angle and rotation speed, Fig. 2 is a perspective view showing the schematic structure of a magnetoresistive thin film magnetic head, and Fig. 3 is a perspective view showing the schematic structure of a magnetoresistive thin film magnetic head. A perspective view illustrating the direction of current and the direction of magnetic field application when a magnetic magnetoresistive film is used in the form of a thin film strip. Figure 4 shows the relationship between the resistance change and the magnetic field when a magnetic field is applied to the ferromagnetic magnetoresistive film. Figure 5 shows Ni-Fe
FIG. 2 is a diagram illustrating a -Co system ternary component diagram and a limited composition range of the present invention. 1... Ferromagnetic magnetoresistive alloy film, 2... Applied magnetic field.

【table】

Claims (1)

[Claims] 1. A ferromagnetic magnetoresistive alloy film made of a Ni-Fe-Co ternary alloy whose weight composition is Ni _lxy
A ferromagnetic magnetoresistive alloy characterized by having a composition range that satisfies two conditions: -Fe _x -Co _y , where x is 0.05≦x and y is 0.15≦y≦0.5−2.5x. film. 2. The ferromagnetic magnetoresistive alloy film according to claim 1, wherein the ferromagnetic magnetoresistive alloy film has a thin film stop shape whose length is sufficiently longer than its width. Effect alloy membrane. 3. The ferromagnetic magnetoresistive alloy film according to claim 1 or 2, which has a film thickness of 20 to 400 nm.