JPH0240972A - Magnetoresistance effect thin film - Google Patents

Abstract

PURPOSE:To obtain a magnetoresistive element of high sensitivity by sufficiently decreasing anisotropic magnetic field by using fine crystal grains of Ni, Fe and Co whose average grain diameters are equal to or less than 30nm. CONSTITUTION:NiFe alloy exhibits an MR ratio, low magnetostriction and small anisotropic magnetic field. NiCo alloy exhibits an remarkably large MR ratio, but the value of isotropic magnetic field is rather large as compared with NiFe. When an alloy thin film is formed by selecting Co concentration, and using, as main component, fine crystal grains of Ni, Fe and Co whose average grain diameters are equal to or less than 30nm, the value of anisotropic magnetic field becomes sufficiently small from the viewpoint of magnetic field detection sensitivity, and exhibits characteristics suitable to a highly sensitive MR element.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to the ferromagnetic magnetoresistive effect (hereinafter abbreviated as MR effect).
A magnetoresistive element (hereinafter referred to as M
The present invention relates to a ferromagnetic magnetoresistive thin film (hereinafter abbreviated as MR film) used in an R element (abbreviated as R element).

(Prior Art) As is well known, MR elements that detect magnetic fields using the MR effect are currently widely used as magnetic sensors, magnetic heads, rotation detection elements, position detection elements, and the like. This M
The MR film, which is the main part of the R element, is made of NiFe or N.
iCo alloy thin films have been widely used. In particular, NiFe
has a small anisotropic magnetic field of about 40 g and exhibits very good soft magnetic properties, so its magnetization responds well to externally applied magnetic fields.For example, it is used as an MR head that uses the MR effect to read out weak signal magnetic fields. It has been considered optimal for

(Problems to be Solved by the Invention) Nowadays, increasing the sensitivity of MR elements is an important issue. Particularly in the field of magnetic recording, there is an urgent need to increase the magnetic field sensitivity of MR heads in order to improve recording density. For this purpose, it is necessary that the anisotropic magnetic field of the MR film has a sufficiently small value. In particular, MR heads require linear response to magnetic fields;
A bias magnetic field is applied to the MR film, but from the viewpoint of ease of bias application, the anisotropic magnetic field of MRs is approximately 10
It is desirable that it be 0e or less.

As mentioned above, NiFe is known as an MR effect material with a small anisotropic magnetic field value, but when seeking higher output in an MR element, it is necessary to find a material that exhibits a larger MR effect than NiFe. desired. NiCo is known as such a material (Fujitsu Science and Technical Journal, 1974, p. 123). However, for NiCo, the anisotropic magnetic field value is approximately 200
The problem is that it cannot be used as a highly sensitive MR material due to its large e.

In view of the above points, the present invention has a small anisotropic magnetic field value,
The present invention aims to provide an MR material suitable for highly sensitive MR elements.

(Means for Solving the Problems) The MR film of the present invention contains Ni, Fe, and Co as main components, and the average grain size of the microcrystal grains constituting the thin film is 30 nm.
m or less.

(Function) Here, in the present invention, the reason why Ni, Fe, and Co are the main components and the average grain size of the microcrystalline grains is limited as described above will be described.

NiFe alloys used as MR materials have relatively large MR ratios, low magnetostriction, and small anisotropy fields. On the other hand, NiCo alloy shows a very large MR ratio,
The value of the anisotropic magnetic field is quite large compared to NiFe. From these facts, in the alloy thin film mainly composed of Ni, Fe, and Co in the present invention, by selecting the Co concentration, it is possible to obtain a larger MR ratio than that of NiFe, and moreover, it is possible to obtain an MR ratio comparable to that of NiFe. It is believed that a small anisotropic magnetic field can be achieved.

FIG. 1 shows the relationship between the anisotropic magnetic field and the crystal grain size (measured using FE-8EM) in this ternary alloy thin film.

The Co concentration of the film is shown above each data point. According to this figure, when the anisotropic magnetic field value is 80e or less, which is considered to be sufficiently small in terms of magnetic field detection sensitivity, the crystal grain size value is 30 nm or less. However, the anisotropic magnetic field is approximately 1
In the film of 70e (NlB□Co18), the crystal grain size is very large, 200 nm. Therefore, by suppressing the crystal grain size to 30 nm or less, the anisotropic magnetic field value can be suppressed to 80e or less.

From the above experimental facts, it is possible to obtain an MR effect thin film suitable for high-sensitivity MR elements by using Ni, Fe, and Co as main components and setting the average grain size of the microcrystalline grains constituting the thin film to 30 nm or less. .

Generally, it is believed that the smaller the crystal grains constituting a thin film, the more suppressed the magnetocrystalline anisotropy is, and the smaller the anisotropic magnetic field of the thin film becomes. Since the crystal grain size of the alloy thin film mainly composed of Ni, Fe, and Co according to the present invention is 30 nm or less, the anisotropic magnetic field value is sufficiently small from the viewpoint of magnetic field detection sensitivity, making it suitable for highly sensitive MR elements. It has come to exhibit excellent properties as a thin film.

(Example 1) FIG. 2 shows an embodiment of the present invention.

In FIG. 2, a Ni82Fe12Co6 (wt%) film having a thickness of 150 nm was deposited on a glass substrate 1 as an MR film.

When the surface of this film was observed using SEM, the crystal grain size was 30 nm. Furthermore, when we measured the magnetic anisotropy using a sample vibrating magnetometer, what was the value of the anisotropic magnetic field? , 8
It was found that the value was 0e, which is a desirable value from the viewpoint of magnetic field detection sensitivity. Next, Au3 was deposited on this film (film thickness: 240 nm). Furthermore, a photoresist pattern was formed on this Au vapor deposited film, and ion etching was performed in an Ar gas atmosphere to form a rectangular pattern 4 as a magnetically sensitive part and an electrode pattern 5 for supplying a sense current. Here, the etching conditions are acceleration voltage:
500V, Ar gas pressure crab I X 10-'Tor
It is r. Furthermore, a photoresist pattern serving as a mask was formed on this pattern, and selective chemical etching was performed to form two MR films into two rectangular patterns each having a length of 2 mm and a width of 511 m, thereby producing an MR element.

The MR element manufactured in this example has a small crystal grain size, so the anisotropic magnetic field is small, and exhibits good soft magnetic properties. Therefore, when an external magnetic field varying on the order of several Oe was applied to this element, higher magnetic field detection sensitivity could be obtained than in the past.

(Example 2) In FIG. 2, NlB2Fel2C was used for MR film formation.
O6 (wt%) in Ar gas at 5X10-3 Torr,
An MR element was produced in the same manner as in Example 1 except that the film was formed by sputtering under the condition of discharge power of 5.0 W/am2.

When the MRR2O crystal grain size was measured, it was <30 nm, the same as in Example 1. In the MR element manufactured in this way as well, high magnetic field detection sensitivity could be obtained as in Example 1.

(Effects of the Invention) As described above, the magnetoresistive thin film of the present invention is made of Ni, F
e, Co as the main component, and the average grain size of the microcrystalline grains constituting the thin film is 30 nm or less, so the anisotropic magnetic field value is sufficiently small from the viewpoint of magnetic field detection sensitivity, and high It can be seen that it is suitable for high-sensitivity MR elements.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic characteristics of the MR film according to the present invention, and is a diagram showing the relationship between crystal grain size and anisotropic magnetic field. FIG. 2 is a diagram showing an embodiment of the present invention. In the figure,

Claims (1)

[Claims] 1. A magnetoresistive thin film containing Ni, Fe, and Co as main components, characterized in that the average grain size of microcrystalline grains constituting the thin film is 30 nm or less.