JP3262697B2 - Magnetoresistance effect multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a magnetoresistive element used in a magnetic head, particularly a reproducing head, or a position sensor or a rotation sensor.

[0002]

2. Description of the Related Art As a conventional magnetoresistive (MR) effect material, a Ni-Fe alloy thin film (permalloy thin film) or the like is used, and the resistance change rate of the permalloy film is 2-3%. In the future, in order to cope with narrower tracks of magnetic heads and higher resolution of magnetic sensors, the rate of change in resistance (MR
Ratio) is desired. In recent years, a phenomenon called giant magnetoresistance (GMR) effect has been discovered in multilayer thin films of Fe / Cr or Co / Cu (see: MNBai).
bich et al., Physical Review Letters, vol. 61 (198
8) Page 2472, DHMosca et al., Journal of Magnetism
andMagnetic Materials, Volume 94 (1991) L1
page). In these thin films, the interface between Fe and Cr or Co and
It is said that the spin-dependent scattering of conduction electrons at the Cu interface contributes to the giant magnetoresistance effect.
The mechanism of MR generation is fundamentally different from Ni-Fe and the like.
These thin films have an MR ratio of 10% or more.

By the way, these magnetoresistance effects (MR)
In a multilayer film, a magnetoresistance (MR) effect (CIP-MR) is generally obtained by flowing a current in a direction in the plane of the multilayer film, but the GMR effect in the magnetoresistance effect multilayer film is as described above. As described above, since conduction electrons are generated by spin-dependent scattering at the interface of the multilayer film, it is more effective to allow more conduction electrons to cross the multilayer film interface. That is, in the magnetoresistive multilayer film, a CIP is applied by flowing a current in a direction perpendicular to the film surface.
It is known that the GMR effect (CPP-MR) can be obtained more effectively than -MR.

[0004]

However, since the total thickness of the magnetoresistive multilayer is generally several hundred nm at most, the resistance in the thickness direction is small and the amount of resistance change due to the GMR effect is increased. I couldn't do that. That is, it was not easy to extract a practically usable output voltage by changing the resistance in the film thickness direction by passing a current in the direction perpendicular to the film surface.

The present invention has been made in view of the above circumstances, and when the direction of current flow is the in-plane direction of the film, the MR effect can be more effectively obtained, and the resistance change due to the GMR effect can be reduced. It is an object of the present invention to provide a magnetoresistive multilayer film that can be made large.

[0006]

In order to solve the above-mentioned problems, the present invention provides a ferromagnetic cluster layer in which ferromagnetic clusters and non-magnetic substances are alternately arranged in a film in-plane direction, Nonmagnetic layers are alternately stacked, the direction of spontaneous magnetization of the ferromagnetic cluster is perpendicular to the film surface, and the direction of spontaneous magnetization of adjacent ferromagnetic clusters in the same layer is antiparallel. This is a magnetoresistive effect multilayer film characterized by the following.

According to a second aspect of the present invention, when the size of the ferromagnetic cluster in the in-plane direction is x and the distance between adjacent ferromagnetic clusters in the same layer is w, 0.7 nm ≦ x ≦ 20 nm 2. The magnetoresistive effect multilayer film according to claim 1, wherein the following relationship is satisfied: 0.3 nm ≦ w ≦ 20 nm. According to a third aspect of the present invention, the size of the ferromagnetic cluster in the in-plane direction is x, the size in the direction perpendicular to the film surface is y, and the distance between adjacent ferromagnetic clusters in the same layer is w. 2. The magnetoresistive effect multilayer film according to claim 1, wherein the following relationship is satisfied: y / x ≧ 1.20.7 nm ≦ x ≦ 20 nm 0.3 nm ≦ w ≦ 20 nm.

According to a fourth aspect of the present invention, the ferromagnetic cluster layer is composed of a number of ferromagnetic clusters made of a Co—Cr alloy and a non-magnetic material made of Cu and / or Ag, and the non-magnetic layer is made of Cu. And / or Ag. 4. The magnetoresistive effect multilayer film according to claim 1, wherein said multilayer film is made of Ag. The invention according to claim 5 is characterized in that the ferromagnetic cluster layer comprises a number of ferromagnetic clusters composed of an alloy containing Co-Cr as a main component and containing Cu and / or Ag, and Cu and / or A
g, and the nonmagnetic layer is made of Cu.
And / or Ag. 4. The magnetoresistive effect multilayer film according to claim 1, wherein said multilayer film is made of Ag.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 is a schematic view showing an example of a cross-sectional state of a magnetoresistive multilayer film of the present invention. In the figure, reference numeral 1 denotes a ferromagnetic cluster layer, 2
Is a non-magnetic layer, 11 is a ferromagnetic cluster, and 12 is a non-magnetic substance. As shown in the figure, the magnetoresistive multilayer film of the present invention is configured by alternately stacking ferromagnetic cluster layers 1 and nonmagnetic layers 2. In the ferromagnetic cluster layer 1, ferromagnetic clusters 11 and non-magnetic substances 12 are alternately arranged in a film surface direction (indicated by a in the drawing). The spontaneous magnetization of the ferromagnetic cluster 11 is oriented in a direction perpendicular to the film surface (indicated by b in the figure), and the direction of the spontaneous magnetization of the adjacent ferromagnetic clusters 11 in the same layer is antiparallel. ing.

[0010] A ferromagnetic cluster layer 1 is formed around a fine cluster 11 made of a ferromagnetic metal material.
It can be preferably configured to have a structure where 2 is deposited. The shape of the ferromagnetic cluster 11 is preferably long in the direction perpendicular to the film surface.
When the size in the direction in the film plane is x and the size in the direction perpendicular to the film plane is y, the aspect ratio (y / x) is 1.
It is preferably two or more. By making the ferromagnetic cluster 11 have such a vertically long shape, the spontaneous magnetization of the ferromagnetic cluster 11 can be directed in a direction perpendicular to the film surface due to shape anisotropy.

Alternatively, the ferromagnetic cluster 11 may be formed such that the ferromagnetic cluster 11 has crystal magnetic anisotropy and the axis of easy magnetization is perpendicular to the film surface. 11 can be directed in a direction perpendicular to the film surface. In this case, the shape of the ferromagnetic cluster 11 does not necessarily have to satisfy the above aspect ratio. The size x of the ferromagnetic cluster 11 in the in-plane direction is preferably 0.7 nm or more and 20 nm or less. When x is 0.7 nm or less, it is difficult to maintain the ferromagnetism of the ferromagnetic cluster 11, and when x is 20 nm or more, the MR effect is significantly reduced.

As the non-magnetic substance 12, a non-magnetic metal element having a tendency to phase-separate from the ferromagnetic metal element constituting the ferromagnetic cluster 11 is preferably used. When the thickness of the nonmagnetic substance 12, that is, the distance between the adjacent ferromagnetic clusters 11 in the same layer is w, w is preferably adjusted to 0.3 nm or more and 20 nm or less. If w is 0.3 nm or less, the spontaneous magnetizations of the adjacent ferromagnetic clusters 11 are all parallel due to direct exchange coupling between the ferromagnetic clusters 11, and the MR effect cannot be obtained. On the other hand, when w is 20 nm or more, the MR effect is significantly reduced.

The nonmagnetic layer 2 may be made of the same material as the nonmagnetic material 12 in the ferromagnetic cluster layer 1, or may be made of a different nonmagnetic material. When the non-magnetic layer 2 is made of the same material as the non-magnetic substance 12 in the ferromagnetic cluster layer 1, there is no scattering of conduction electrons at the interface between different kinds of non-magnetic substances (irrespective of the MR effect). An MR effect can be obtained. If the thickness of the nonmagnetic layer 2 is too large, another interface (an interface contributing to the MR effect)
The probability of conduction electrons passing only through the non-magnetic layer 2 without causing scattering of conduction electrons at this time is increased, which is not preferable because the MR effect is reduced. If it is too thin, the upper and lower ferromagnetic clusters 11 directly As a result of the exchange coupling, the magnetizations of the adjacent ferromagnetic clusters 11 become parallel. (This is because the positional relationship between the upper and lower ferromagnetic clusters 11 is generally shifted, so that, for example, one upper ferromagnetic cluster 11
Direct exchange coupling, the magnetizations of the two lower ferromagnetic clusters 11 must be parallel. Therefore, it is preferable to appropriately set the size and distribution of the ferromagnetic clusters 11 (whether or not the ferromagnetic clusters 11 are regularly arranged vertically).

The magnetoresistive effect multilayer film of the present invention is obtained by alternately forming a nonmagnetic layer 2 and a ferromagnetic cluster layer 1 on a substrate by using a general-purpose multilayer film manufacturing technique, for example, a thin film forming apparatus such as sputtering or vapor deposition. It can be manufactured by forming a film. For example, as a film forming apparatus, a high frequency bipolar sputtering apparatus, DC sputtering, magnetron sputtering, tripolar sputtering, ion beam sputtering, facing target type sputtering, or the like can be used. When forming the ferromagnetic cluster layer 1, it is preferable to form an alloy thin film using a ferromagnetic metal element and a non-magnetic metal element having a tendency to phase separate from the ferromagnetic metal element. This makes it possible to obtain a structure in which the nonmagnetic substance 12 is segregated at the grain boundaries of the ferromagnetic crystal (ferromagnetic cluster 11) by the heat treatment after the film formation or after the film formation.

When forming the ferromagnetic cluster layer 1, the film forming conditions are controlled so that the axis of easy magnetization of the magnetocrystalline anisotropy of the ferromagnetic cluster 11 is perpendicular to the film surface. Is preferred. In this way, the spontaneous magnetization of the ferromagnetic cluster 11 can be directed in the direction perpendicular to the film surface by the crystal magnetic anisotropy. Alternatively, the alloy composition and the film forming conditions may be controlled so that the shape of the ferromagnetic cluster 11 becomes longer in the direction perpendicular to the film surface. In this case, the spontaneous magnetization of the ferromagnetic cluster 11 can be directed in the direction perpendicular to the film surface due to the shape anisotropy. Further, the thickness of the nonmagnetic substance 12 precipitated at the grain boundary of the ferromagnetic cluster 11 can be controlled by appropriately setting the alloy composition, film forming conditions, heat treatment conditions, and the like when forming the ferromagnetic cluster layer 1. it can. Thereby, the spontaneous magnetization of the adjacent ferromagnetic clusters 11 in the same layer can be made antiparallel by the exchange interaction or the magnetostatic interaction via the nonmagnetic material 12.

The preferred composition of the magnetoresistive multilayer film of the present invention is, for example, that the ferromagnetic cluster layer 1 is made of Co—C
The non-magnetic layer 2 is composed of a number of ferromagnetic clusters 11 made of an r alloy and a non-magnetic substance 12 made of Cu and / or Ag, and the non-magnetic layer 2 is made of Cu and / or Ag. When a Co—Cr alloy is used as the ferromagnetic cluster 11, the Co—Cr alloy forms a hexagonal columnar crystal, and thus has a shape that is long in a direction perpendicular to the film surface and has a crystal magnetic anisotropic property. Cluster 11 in which the easy axis of magnetization is oriented perpendicular to the film plane can be formed relatively easily. In this case, when the ferromagnetic cluster layer 1 is formed, it is preferable to select a film forming condition in which columnar crystals are easily formed, such as high Ar pressure sputtering. As the non-magnetic substance 12, Cu and / or Ag, which is easily phase-separated from Co, can be preferably used, and a structure in which the non-magnetic substance 12 is deposited around many ferromagnetic clusters 11 can be obtained. The ferromagnetic cluster 11 has C
It may contain o-Cr as a main component and trace amounts of Cu and / or Ag.

According to the magnetoresistive multilayer film of the present invention, when a current flows in an in-plane direction of the film, a large number of conduction electrons can cross the interface between the ferromagnetic cluster 11 and the non-magnetic substance 12. The same effect as that of the CPP-MR can be obtained, and the GMR effect can be obtained more effectively than the conventional CIP-MR. Moreover, in the conventional CPP-MR, the current flows in the film thickness direction, whereas in the magnetoresistive multilayer film of the present invention, the current flows in the
Since the effect is obtained, the amount of change in resistance can be increased.

[0018]

【Example】

(Embodiment 1) It corresponds to the magnetoresistive effect multilayer film of the present invention.
Co ₆₀ Cr ₁₇ Cu ₂₃ (atomic%) alloy composition thickness 10
nm ferromagnetic cluster layer and 3 nm thick non-magnetic Cu
A multilayer film was formed by alternately laminating the layers for 20 cycles (ie, 40 layers in total). (Hereinafter, [Co ₆₀ Cr ₁₇ Cu ₂₃ (10 nm)
/ Cu (3 nm)] ₂₀ . The film was formed using a high frequency bipolar sputtering apparatus. The film forming conditions were as follows: high frequency input: 2.4 × 10 ⁴ W / m ² , Ar gas pressure: 5 mTorr, substrate: water-cooled. , 400 ° C
For 1 hour. Of the obtained multilayer film,
The state of spontaneous magnetization of the ferromagnetic cluster, the size in the in-plane direction (x), the size in the direction perpendicular to the film surface (y), the distance between adjacent ferromagnetic clusters in the same layer (w), and the resistance The rate of change (△ ρ / ρ) is shown in Table 1 below.

(Example 2) In the same manner as in Example 1,
[Co ₆₃ Cr ₁₇ ] corresponding to the magnetoresistive effect multilayer film of the present invention.
Ag ₂₀ (10 nm) / Ag (3 nm)] A multilayer film having a film configuration of ₂₀ was formed. In the obtained multilayer film, the state of spontaneous magnetization of the ferromagnetic cluster, the size in the in-plane direction (x), the size in the direction perpendicular to the film surface (y), and the size of the adjacent ferromagnetic cluster in the same layer Table 1 below shows the interval (w) and the rate of change in resistance (） ρ / ρ).

(Embodiment 2) In the same manner as in Embodiment 1,
[Co ₆₀ Cr ₁₇ ] which corresponds to the magnetoresistive multilayer film of the present invention.
Cu ₂₃ (10 nm) / Ag (3 nm)] ₂₀ was formed. In the obtained multilayer film, the state of spontaneous magnetization of the ferromagnetic cluster, the size in the in-plane direction (x), the size in the direction perpendicular to the film surface (y), and the size of the adjacent ferromagnetic cluster in the same layer Table 1 below shows the interval (w) and the rate of change in resistance (） ρ / ρ).

(Comparative Example 1) As a comparative example, the above Example 1 was used.
[Co ₈₀ Cr ₂₀ (5 nm) / Cu (3 nm)] ₂₀
A multilayer film having the following film configuration was formed. In the obtained multilayer film, the state of spontaneous magnetization of the ferromagnetic cluster, the size in the in-plane direction (x), the size in the direction perpendicular to the film surface (y), and the size of the adjacent ferromagnetic cluster in the same layer Table 1 below shows the interval (w) and the rate of change in resistance (） ρ / ρ).

[0022]

[Table 1]

From the results shown in Table 1, the multilayer films of Examples 1 to 3 have a large resistance change rate of as much as 8% to 12%, whereas Comparative Example 1 [Co ₈₀ Cr ₂₀ (5 nm)]. / Cu (3n
m)] ₂₀ shows that only a 2% resistance change rate was obtained. Therefore, it is clear that the magnetoresistance effect multilayer film of the present invention has an excellent magnetoresistance effect.

[0024]

As described above, the magnetoresistive multilayer film of the present invention comprises a ferromagnetic cluster layer in which ferromagnetic clusters and non-magnetic substances are alternately arranged in a film plane direction, and a non-magnetic layer. The ferromagnetic clusters are alternately stacked, and the direction of the spontaneous magnetization of the ferromagnetic cluster is perpendicular to the film surface, and the direction of the spontaneous magnetization of an adjacent ferromagnetic cluster in the same layer is antiparallel. It is. Therefore, when a current flows in the in-plane direction of the film, conduction electrons can traverse the interface between the ferromagnetic cluster and the non-magnetic material much, so that the same operation as the conventional CPP-MR is obtained, and the conventional CIP-MR is obtained. −
The GMR effect can be obtained more effectively than MR. In addition, since the GMR effect can be obtained with the direction of the current being the in-plane direction of the film, a large resistance change amount can be obtained.
Therefore, it is possible to obtain a highly sensitive magnetic head, a magnetic sensor, and the like that can obtain a high output with a lower magnetic field.

When the size of the ferromagnetic cluster in the in-plane direction is x and the distance between adjacent ferromagnetic clusters in the same layer is w, 0.7 nm ≦ x ≦ 20 nm 0.3 nm ≦ w ≦ By setting the thickness to 20 nm, the ferromagnetism of the ferromagnetic cluster is maintained, and the spontaneous magnetization of the adjacent ferromagnetic cluster is maintained antiparallel, so that a preferable MR effect can be obtained.

Further, in addition to the above conditions of x and w, when the size of the ferromagnetic cluster in the direction perpendicular to the film surface is y, the shape anisotropy is obtained by satisfying y / x ≧ 1.2. Due to the nature, the spontaneous magnetization of the ferromagnetic cluster 11 can be directed in a direction perpendicular to the film surface.

The ferromagnetic cluster layer is composed of a number of ferromagnetic clusters made of a Co—Cr alloy, Cu and / or A
g and a non-magnetic layer made of Cu and / or Ag, the Co-Cr alloy forms a hexagonal columnar crystal. It is possible to relatively easily form a ferromagnetic cluster having a shape that is long in the vertical direction and whose easy axis of crystal magnetic anisotropy is oriented perpendicular to the film surface. In addition, Cu and / or Ag are easily phase-separated from Co, so that the structure according to claim 1 can be suitably obtained.

Alternatively, the ferromagnetic cluster layer is made of Co-
A plurality of ferromagnetic clusters composed of an alloy containing Cu as a main component and containing Cu and / or Ag, and a nonmagnetic substance made of Cu and / or Ag, wherein the nonmagnetic layer is made of Cu and / or A
g may be adopted. In this case, the structure according to claim 1 can be suitably obtained in the same manner as the structure according to claim 4.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a state of a cross section of a magnetoresistive multilayer film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ferromagnetic cluster layer 2 Nonmagnetic layer 11 Ferromagnetic cluster 12 Nonmagnetic substance

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 43/08 G01R 33/09 G11B 5/39 H01F 10/08 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A ferromagnetic cluster layer in which ferromagnetic clusters and non-magnetic substances are alternately arranged in a film plane direction, and a non-magnetic layer are alternately stacked, and the direction of spontaneous magnetization of the ferromagnetic cluster is A magnetoresistive multilayer film which is perpendicular to the film surface and in which the directions of spontaneous magnetization of adjacent ferromagnetic clusters in the same layer are antiparallel. 2. When the size of the ferromagnetic cluster in the film plane direction is x and the distance between adjacent ferromagnetic clusters in the same layer is w, 0.7 nm ≦ x ≦ 20 nm 0.3 nm ≦ w ≦ The magnetoresistive multilayer film according to claim 1, wherein a relationship of 20 nm is satisfied. 3. When the size of the ferromagnetic cluster in the in-plane direction is x, the size in the direction perpendicular to the film surface is y, and the distance between adjacent ferromagnetic clusters in the same layer is w. 2. The magnetoresistive effect multilayer film according to claim 1, wherein the following relationship is satisfied: y / x ≧ 1.2 0.7 nm ≦ x ≦ 20 nm 0.3 nm ≦ w ≦ 20 nm. 4. The ferromagnetic cluster layer is made of Co—Cr.
A plurality of ferromagnetic clusters composed of an alloy and a non-magnetic substance composed of Cu and / or Ag,
4. It is made of u and / or Ag.
The magnetoresistive effect multilayer film as described in the above. 5. The ferromagnetic cluster layer is made of Co—Cr.
A plurality of ferromagnetic clusters composed of an alloy containing Cu and / or Ag as a main component, and a nonmagnetic substance composed of Cu and / or Ag, wherein the nonmagnetic layer is composed of Cu and / or Ag. Item 4. The magnetoresistive effect multilayer film according to items 1 to 3.