JPH0697532A - Magnetoresistance effect element - Google Patents

Abstract

PURPOSE:To obtain a magnetoresistance effect element of high magnetic sensitivity, by making the direction of the axis of easy magnetization of a magnetically soft film intersect the direction of the axis of easy magnetization of a hard film. CONSTITUTION:In a magnetoresistance element wherein a specified number of magnetically soft films composed of, e.g. Ni-Fe alloy and magnetically hard films composed of, e.g. Co, are laminated, the direction of the axis of easy magnetization of the soft films is made to intersect the direction of the axis of easy magnetization of the hard films, in the range from 0 deg. to + or -180 deg.. Thereby the magnetic coupling force to the hard film is decreased, and the magnetization direction of the soft film becomes easy to be changed by an external magnetic field, so that a magnetoresistance effect element of high magnetic sensitivity can be obtained. The figure shows the directions of the axes of easy magnetization of the soft film (Ni-Fe alloy film) and the hard film (Co film) just after film formation, during application of high intensity magnetic field, and after removal of the high intensity magnetic field. Finally an element is obtained in which the direction of the axis of easy magnetization of the soft film intersects that of the hard film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive effect element (so-called MR element) used in, for example, a magnetic head or a magnetic sensor, and in particular, magnetically hard films and soft films are alternately laminated. The present invention relates to a laminated magnetoresistive effect element including the artificial lattice film.

[0002]

2. Description of the Related Art A magnetically soft magnetic material such as a Ni--Fe alloy (permalloy) is capable of electrically detecting a weak magnetic field change and is therefore used for, for example, a magnetic head or a magnetic sensor. Yes, research and development are underway.

In order to improve the performance of MR elements, research and development of materials having higher magnetic field sensitivity are desired, and recently, in artificial lattice films such as Fe / Cr and Co / Cu, so-called giant magnetoresistive effect has been obtained. Has been discovered.

[0004]

However, in the conventional artificial lattice film, a material having a sufficiently high magnetic field sensitivity (modulation degree) has not been obtained yet. The main reason for this is that as a stable state of the magnetization when the external magnetic field is zero, the magnetizations of the adjacent magnetic layers are directed in opposite directions, so that the so-called antiferromagnetic arrangement is realized. This is because the film thickness condition that causes ferromagnetic coupling is selected.

An object of the present invention is to solve the above problems and to provide a magnetoresistive element having a high magnetic field sensitivity.

[0006]

In order to achieve the above object, the present invention provides a magnetically soft film made of, for example, a Ni--Fe alloy and a magnetically hard film made of, for example, Co. In the magnetoresistive effect element having a predetermined number of laminated layers, the easy axis of magnetization of the soft film intersects the easy axis of magnetization of the hard film within a range of ± 0 ° to ± 180 °. It is what

[0007]

As described above, according to the present invention, the direction of easy magnetization of the soft film intersects with the direction of easy magnetization of the hard film at a predetermined angle so that the magnetic coupling force with the hard film is increased. And the magnetization direction of the soft film is easily changed by an external magnetic field, so that a magnetoresistive effect element having high magnetic field sensitivity can be provided.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 is a perspective view of a magnetic head according to an embodiment, and FIG. 2 is an enlarged cross-sectional view of a laminated magnetoresistive effect element used for the magnetic head.

As shown in FIG. 1, a magnetic head according to an embodiment of the present invention includes a strip-shaped laminated magnetoresistive effect element 1,
It is mainly composed of electrodes 2 and 2 joined to both ends thereof.

As shown in FIG. 2, the laminated magnetoresistive effect element 1 comprises a substrate 3 made of glass or ceramic and a multilayer film 4 made of Ni--Fe / Cu / Co / Cu system formed thereon. It is configured.

The multilayer film 4 will be described in detail. A magnetically soft film 5 made of a Ni--Fe alloy (permalloy) having a film thickness of 30Å and a magnetic insulating film made of Cu having a film thickness of 60Å. 6, a magnetically hard film 7 made of Co having a film thickness of 30 Å, and a magnetic insulating film 8 made of Cu having a film thickness of 60 Å have a minimum unit laminate 9 of several layers or more.
It is formed by repeating several tens of layers.

The multi-layer film 4 is formed by sequentially depositing it to a predetermined film thickness by, for example, ultra-high vacuum electron beam evaporation, but it may be formed by using another thin film forming technique such as sputtering. .

By the way, when the soft film 5 and the hard film 7 are formed, they are formed in a state in which a magnetic field is applied in a direction having a certain angle with respect to the respective easy magnetization axis directions. An example of the magnetic field application direction at this time will be described with reference to FIG.

That is, as shown in (a) of the figure, when the first soft film 5 (Ni-Fe alloy film) is first formed, an angle (+ θ) with respect to the easy axis direction Re of the soft film 5 is formed. ) Is applied while a magnetic field is applied in the direction.

Next, when forming the first hard film 7 (Co film), as shown in (b) of the same drawing, while applying a magnetic field in a direction orthogonal to the easy axis direction Re of the magnetization direction. Form a film.

Next, when the second soft film 5 (Ni-Fe alloy film) is formed, as shown in FIG.
The film is formed while applying a magnetic field in a direction having a certain angle (−θ) with respect to the easy magnetization axis direction Re thereof.

Next, when the second hard film 7 (Co film) is formed, a magnetic field is applied in a direction orthogonal to the easy axis direction Re of the magnetization as shown in (d) of FIG. Form a film.

Next, the third soft film 5 is shown in FIG.
In the same direction as + θ, the fourth soft film 5 has a −θ angle in the same manner as in (c) of FIG. The film is formed by alternately changing the angle and applying the magnetic field, while the hard film 7 is always formed by applying the magnetic field in the direction orthogonal to the easy axis direction Re. The magnetic field in forming the soft film 5 and the hard film 7 is, for example, several hundred Oe or more.

After the multilayer film 4 having a predetermined number of layers is formed in this way, the easy magnetization axis direction R is obtained as shown in FIG.
A strong magnetic field is applied once in a direction perpendicular to the plane e (direction of arrow X), and then the strong magnetic field is removed.

By doing so, the angle α between the directions of the easy axis of magnetization of the soft film 5 and the hard film 7 (the direction of stable magnetization when the external magnetic field is zero) when used as a magnetoresistive effect element. Can have This angle α is ±
It can be appropriately selected within the range of 0 ° to ± 180 °, and in particular, the angle α is 30 ° or more, preferably the angle α is 45.
When it is at least 0 °, more preferably at 60 to 120 °, even higher magnetic field sensitivity can be obtained.

In the above-mentioned embodiment, when the soft film 5 was formed, the magnetic field was applied by alternately changing the angles such as + θ and -θ with respect to the easy magnetization axis direction Re thereof, but the present invention is not limited to this. However, for example, the first soft film 5 to the mth soft film 5 have a magnetization easy axis direction R
The film is formed while applying a magnetic field in a direction having an angle of + θ with respect to e, and from the (m + 1) th soft film 5 to the nth soft film 5 of −θ with respect to the easy magnetization axis direction Re. A plurality of groups (in this case, every two groups), such as when forming a film while applying a magnetic field in an angled direction
It is also possible to change the direction of application of the magnetic field.

By making an angle α between the easy magnetization axis directions of the soft film and the hard film in this way, the magnetization of the soft film 5 is not magnetically strongly coupled to the hard film 7 as shown in FIG. In addition, since the direction of the external magnetic field Y is perpendicular to the easy magnetization axis direction Re in the plane, the direction of the magnetization M is easily changed by the external magnetic field Y, and therefore the magnetoresistive effect having high magnetic field sensitivity is obtained. The device is obtained. Note that arrow E in FIG. 4 indicates the direction of current.

The hard film is composed of a ferrimagnetic ferromagnetic transition metal-rare earth metal alloy whose compensation temperature is around the temperature at which the magnetoresistive effect element is used, and the initialization is deviated from the compensation temperature of the ferrimagnetic material. It is recommended to carry out at a temperature at which the coercive force is relatively small. By doing so, for example, when the magnetoresistive effect element is used as a magnetic head or the like, the operating temperature is near the compensation temperature as described above, and the total magnetization at that temperature is small. It has the feature that adverse effects on the medium can be eliminated.

As described above, in the giant magnetoresistive artificial lattice film in which the soft film and the hard film are alternately laminated, the property that antiferromagnetic coupling is generated between the soft film and the hard film is strong. It may be difficult to control the easy axis of magnetization in the soft film (the stable direction of magnetization when the external magnetic field is zero) to an arbitrary direction.

By the way, when the crossing angle between the easy axis of magnetization of the soft film and the easy axis of magnetization of the hard film in the case of a magnetoresistive effect element is α, the change of the resistance R when α changes by Δα ΔR is given by the following equation.

ΔR / average value R = K · sin α · Δα K: constant determined by the material and structure of the element In order for the magnetoresistive effect element to obtain sufficient magnetic field sensitivity, the crossing angle α is ± 0 ° as described above. Must be an arbitrary value within the range from ± 180 °.

Here, the magnetic interaction between the soft film and the hard film is alternately made ferromagnetic and antiferromagnetic so that the soft film disposed in the middle of the upper and lower hard films has both sides. Magnetic interactions in opposite directions work and cancel each other out. Therefore, when the magnetic field is applied to the soft film to give the magnetic anisotropy as described above, it becomes easy to set the easy axis of magnetization of the soft film to an arbitrary direction.

An embodiment of this will be described with reference to FIG. As shown in the figure, a Cr film 10 is formed on a substrate 3 such as glass.
And the Co film 11 are formed, (Cu / Ni-Fe / C
The laminated body 12 of the minimum unit of (u / Co) is formed with a film thickness of several Å to several tens of Å by repeating a predetermined number of layers.

More specifically, first, the Cr film 10 having a film thickness of 30Å and the Co film having a film thickness of 30Å are formed on the substrate 3. Thereafter, a magnetic insulating film 8 made of Cu having a film thickness of t ₁ and a Ni-Fe alloy (permalloy) having a film thickness of 30 Å
A minimum unit composed of a magnetically soft film 5 made of Cu, a magnetic insulating film 6 made of Cu having a film thickness of t ₂ and a magnetically hard film 7 made of Co having a film thickness of 30Å. The laminated body 12 of is formed by repeating a predetermined number of times.

When the thickness of the insulating film 8 is t ₁ and the thickness of the insulating film 6 is t ₂ , the magnetic interaction between the soft film 5 and the hard film 7 is ferromagnetic and antiferromagnetic. Is set to a value that will Specific examples of the thicknesses t ₁ and t ₂ of the insulating films 6 and 8 are shown in the following table.

The thickness t ₁ of the insulating film 8 is t ₂ 0 to 5Å 6 to 12 Å 12 to 17 Å 18 to 25 Å 25 to 30 Å 31 Å or more The soft axis direction of the soft film 5 and the hard film 7 is The films are oriented in almost the same direction as the direction of the magnetic field applied during the deposition of each film, and in particular, uniaxial magnetic anisotropy is induced in the soft film 5 in that direction.

Next, a magnetic field of a sufficiently strong magnetic field (to the extent of being oriented in the direction of the magnetic field that applies the easy axis of magnetization of the hard film 7, preferably several thousand Oe or more) is applied in an arbitrary direction within the plane, The axis of easy magnetization of the hard film 7 is oriented in a desired direction. At this time, the easy axis of magnetization of the soft film 5 is also oriented in the direction of the applied magnetic field, but if the magnetic field is removed, the easy axis of magnetization of the hard film 7 remains in the direction of the applied magnetic field, but the easy axis of magnetization of the soft film 5 is easy. The upper and lower hard films 7 in the axial direction
Since the interaction with and is almost cancelled, the soft film 5 stabilizes in the direction of the easy axis of magnetization.

Thus, the direction of the easy axis of magnetization of the soft film 5 is
Since it is governed by the uniaxial magnetic anisotropy induced by it, it reacts extremely sensitively to an external magnetic field in the vertical direction, and its magnetization direction changes.

FIG. 6 shows the easy axis directions of magnetization immediately after the formation of the soft film (Ni-Fe alloy film) and the hard film (Co film), during the application of the strong magnetic field and after the removal of the strong magnetic field. It is a figure. As shown in this figure, finally, a film in which the easy axis of magnetization of the soft film (Ni—Fe alloy film) intersects the easy axis of magnetization of the hard film (Co film) is obtained.

When the magnetoresistive effect element according to the present invention is used as a magnetic head, in order to avoid a disturbing effect on the magnetic recording medium due to the magnetization of the hard film, the easy axis of magnetization of the hard film is directed to the recording surface of the medium. It is advantageous to make it approximately horizontal.

By the way, the easy axis of magnetization of the hard film is made substantially horizontal to the recording surface of the medium, and the easy axis of magnetization of the soft film is made substantially perpendicular to the recording surface of the medium. If oriented, the magnetic field sensitivity of the soft film to the leakage magnetic field from the magnetic recording medium becomes weak. On the other hand, the easy axis of magnetization of the hard film is made substantially horizontal to the recording surface of the medium, and the crossing angle of the easy axis of magnetization of the soft film with respect to the hard film is set to 1
If the angle is set to 5 ° to 45 °, preferably about 30 °, it is possible to manufacture a magnetic head which sufficiently reacts to the leakage magnetic field from the magnetic recording medium and has a large magnetoresistive effect.

When the magnetoresistive effect element is used as a magnetic head, a magnetic flux perpendicular to the recording surface of the magnetic recording medium is detected. Therefore, it is efficient to set the easy axis of magnetization of the soft film so as to be perpendicular to the recording surface when the external magnetic field is zero.

As described above, in order to provide an appropriate crossing angle between the easy axis of magnetization of the soft film and the easy axis of magnetization of the hard film, the magnetization of the hard film must have a perpendicular component to the recording surface. I won't. At this time, if all the easy magnetization axis directions of the hard film are set parallel to the same direction, the magnetic flux generated from the end face of the magnetic head (multilayer magnetoresistive effect element) easily disturbs the magnetization of the magnetic recording medium.

If the effective total layer thickness teff of the magnetic head (multilayer magnetoresistive effect element) is smaller than the effective spacing hf between the magnetic head (multilayer magnetoresistive effect element) and the magnetic recording medium, then Little impact. The criterion is given by the equation (1) shown in FIG.

In the above formula (1), hf varies depending on the magnetic recording / reproducing apparatus and the like, but is generally 10 to 50 nm for the type in which the magnetic head and the magnetic recording medium are in contact with each other.

When each item in the equation (1) is set to a value as shown in FIG. 8, it becomes equation (3) in the figure, and this value exceeds the coercive force in the perpendicular direction in the magnetic recording medium. I will end up.

In order to solve this problem, in the embodiment of the present invention, the hard films are divided into groups so that the perpendicular components of the magnetization thereof cancel each other out.

FIG. 9 schematically shows this state. In FIG. 9, 14 is an electric insulating layer made of, for example, plastics, and 15 is a medium facing surface. As shown in the figure, in this example, a hard film (H) 5, a magnetic insulating film 6, a soft film (S) 7, a magnetic insulating film 8,
The hard film (H) 5, the magnetic insulating film 6, and the soft film (S) 7 constitute a minimum unit laminate 15. The laminated bodies 15 are repeatedly arranged a predetermined number of times, and the electrical insulating layers 13 are interposed between the laminated bodies 15 to electrically insulate the laminated bodies 15.

Then, as shown in FIG.
In (A1), the perpendicular component of the magnetization of the hard film (H) 5 faces downward as shown by the arrow, and the second laminated body 1 adjacent to the perpendicular direction.
5 (B1), the perpendicular components of the magnetization of the hard film (H) 5 are directed upward, and the perpendicular components of the magnetization cancel each other for each group. At this time, the relational expression shown in FIG. 10 must be satisfied. In the third embodiment, the easy axis of magnetization of the hard film is alternately reversed for every plural pairs of the soft film and the hard film, and the electrically insulating layer is provided for every plural pairs thereof. The easy axis direction may be alternately reversed for each pair of the soft film and the hard film, and the electrically insulating layer may be provided for each pair.

FIG. 11 is an electric circuit diagram of the magnetic head constructed as described above. A group A (A1, A2 ... A) in which the perpendicular component of the magnetization of the hard film is directed downward at the terminal 16 is shown.
n) are connected to each other, and the group 17 (B1, B1) in which the perpendicular component of the magnetization of the hard film is directed upward to the terminal 17.
2 ... Bn) are connected respectively.

As described above, since the perpendicular components of the magnetization of the hard film are opposite for each group, the way of changing the resistance is opposite, so that the circuit configuration as shown in FIG. From, an output proportional to the resistance difference between the A group and the B group is obtained. In addition, 18 in the figure
Is the magnetic sensitive part of the magnetic head and corresponds to the track width.

In the above embodiment, Ni-Fe / Cu /
Although the Co-based material has been described, the present invention is not limited to this. For example, Cu / Cu / Co-based, F
e / Cr system, Ag / Co system, Ni / Ag system, Fe / Co
/ Cu / Fe system, Co / Cu system, Cu / Co system / Cu /
It is also possible to use a material such as Ni-Fe system.

[0048]

As described above, according to the present invention, the easy axis of magnetization of the soft film is crossed with the easy axis of magnetization of the hard film at a predetermined angle so as to be magnetically coupled with the hard film. The binding force is weakened, and the magnetization direction of the soft film is likely to change due to an external magnetic field. Therefore, a magnetoresistive effect element having high magnetic field sensitivity can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view of a magnetic head according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a laminated magnetoresistive effect element used for the magnetic head.

FIG. 3 is an explanatory diagram for explaining a magnetic field application direction of each film in the laminated magnetoresistive effect element.

FIG. 4 is an explanatory diagram for explaining a usage mode of the laminated magnetoresistive effect element.

FIG. 5 is an enlarged sectional view of a laminated magnetoresistive effect element according to a second embodiment.

FIG. 6 is an explanatory view showing the easy axis direction of magnetization immediately after film formation of each film in the laminated magnetoresistive effect element, during application of a strong magnetic field and after removal of the magnetic field.

FIG. 7 is a diagram showing mathematical expressions.

FIG. 8 is a diagram showing specific numerical values and expressions in the expressions.

FIG. 9 is an enlarged sectional view of a laminated magnetoresistive effect element according to a third embodiment.

FIG. 10 is a diagram illustrating a mathematical formula.

FIG. 11 is an electric circuit diagram of the magnetic head according to the third embodiment.

[Explanation of symbols]

 1 Multilayer Magnetoresistive Element 4 Multilayer Film 5 Soft Film 6, 8 Magnetic Insulating Film 7 Hard Film 9, 12, 15 Minimum Unit Laminate 13 Electrical Insulating Film

Claims (5)

[Claims] 1. In a magnetoresistive element in which a predetermined number of layers of a magnetically soft film and a hard film are laminated, the easy axis of magnetization of the soft film intersects the easy axis of magnetization of the hard film. A magnetoresistive effect element characterized in that 2. The magnetoresistive effect element according to claim 1, wherein the easy axis of magnetization of the soft film alternates in the stacking direction of the films. 3. The magnetoresistive element according to claim 1, wherein the easy axis of magnetization of the soft film is different for each group in the laminating direction of the film. 4. The magnetoresistive effect element according to claim 1, wherein the magnetic interaction between the soft film and the hard film is alternately made ferromagnetic and antiferromagnetic. 5. The magnetic film according to claim 1, wherein the easy magnetization axis directions of the hard film and the soft film and the hard film are alternately reversed for each pair or plural pairs. A magnetoresistive effect element characterized in that an electrical insulating layer is provided for each.