JPH06231989A - Manufacture of magnetic thin film - Google Patents

Abstract

PURPOSE:To obtain even in a thin film the same antiferromagnetism- ferromagnetism transition characteristic as a bulk by forming an alloy thin film having a specified Rh component by a method wherein layers of different Rh components are deposited alternately and then these layers are heat-treated to unify the Rh component in a thin film. CONSTITUTION:On a substrate 2, a layer 1a having 0-35at% of Rh and 100-65at% of Fe and a layer 1b having 65-100at% of Rh and 35-0at% of Fe are deposited by turns. After that, these layers are heat-treated to unify the composition in a thin film. Then, an alloy thin film 3, principal ingredients of which are 45-55at% of Rh and 55-45at% of Fe, is obtained. While depositing the thin film, the temperature of the substrate is kept at 100-1000 deg.C. While heat treatment is conducted for unification of the composition, tensile stress is applied to the thin film. By this method, the same antiferromagnetism- ferromagnetism transition characteristic as a bulk can be obtained even in a thin film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnetic thin film applicable to various sensors, actuators and the like.

[0002]

2. Description of the Related Art An alloy having a composition in the vicinity of Fe-50 at% Rh is a CsCl type body centered cubic lattice.
Hereinafter referred to as bcc) It becomes an ordered alloy. This ordered alloy is
It is antiferromagnetic at low temperatures, but transitions to ferromagnetism at 60 ° C to 100 ° C. Since about 1100 G of magnetization is generated discontinuously from the state of zero magnetization, there are many possible applications such as a temperature sensor and a heat-sensitive actuator. If this ordered alloy can be formed in a thin film form, it is expected that the range of application will be further expanded. However, there are great difficulties in forming this alloy as a thin film. Figure 7 is a journal published by JM Lommel in 1966.
It shows the temperature change of the magnetization of the Fe-50 at% Rh composition alloy thin film, which was announced in Vol. 37, page 1483 of The Applied Physics. As can be seen from the figure, the thin film has a large temperature hysteresis as compared with the bulk material, and the magnetization transition is widened. Such an unclear characteristic of the magnetization transition causes a decrease in sensitivity, resolution, etc. when applied to a sensor or the like, and has a disadvantage that it can be applied only to a very limited purpose.

[0003]

The present invention has been proposed to solve the above-mentioned drawbacks, and an object thereof is to provide a method for producing a FeRh ordered alloy thin film exhibiting a sharp magnetization transition almost equivalent to bulk characteristics. To provide. First, the reason why the thin film behaves differently from the bulk in the prior art will be described. Generally, since thin film formation is vapor phase growth, it is difficult to obtain an equilibrium phase, and a high temperature phase is often formed. That is, the liquid state is rapidly cooled, and Rh is 50 at% and Fe is the remaining 50 at%.
Is a non-magnetic face-centered cubic lattice (face
A thin film having a centered cubic (hereinafter referred to as fcc) structure is easily obtained. Therefore, in order to obtain the target ordered alloy, heat treatment is performed after the thin film is formed, and bc is obtained from the fcc structure.
It must be transformed into the c structure. b from fcc structure
In the process of changing to a cc structure, shearing deformation and volume expansion occur. In the case of a thin film, since the film is in close contact with the substrate, the compressive stress is increased, and the deformation and volume expansion cannot be sufficiently performed, so that the entire thin film is not transformed and the untransformed fcc phase remains. It will be. This residual fcc phase hinders the crystal growth of the transformed bcc phase, resulting in the formation of many irregularly arranged portions and defects, so that the antiferromagnetic state becomes unstable and the magnetization transition becomes unclear. is there. The present invention is a technique for solving the above problems peculiar to the thin film of the FeRh ordered alloy.

[0004]

In order to achieve the above object, the present invention is such that Rh is 0 to 35 at% and Fe is the remaining 10%.
0 to 65 at% composition layer and Rh 65 to 100 at
%, Fe are alternately deposited with the remaining 35 to 0 at% composition layer, and then heat treatment is performed to make the composition uniform in the thin film. Rh is 45 to 55 at% and Fe is 55 to 4 at%.
The gist of the invention is a method for producing a magnetic thin film, which comprises forming an alloy thin film containing 5 at% as a main component.

[0005]

In the present invention, Rh is 0 to 35 at%, F
e is the remaining 100 to 65 at% composition layer and Rh is 65
˜100 at%, Fe is alternately deposited with the remaining 35 to 0 at% composition layer, and then heat treatment is performed to make the composition uniform in the thin film, Rh is 45 to 55 at%, and Fe is the remaining 55. By forming an alloy thin film whose main component is ˜45 at%, an antiferromagnetic-ferromagnetic transition characteristic similar to that of bulk can be obtained even in the thin film.

[0006]

EXAMPLES Next, examples of the present invention will be described. Figure 1
(A) shows the structure of the thin film in this invention. In the figure, thin films 1a and 1b are formed in a multilayer structure on a substrate 2. The first and odd layers (1a in the figure) are Fe-rich layers with a Rh composition of 35 at% or less, and the second layers and the even layers (1b in the figure) are Rh-rich layers with a Rh composition of 65 at% or more. I do. 3 indicates the deposited thin film. The composition of the thin film is Fe-45 to 5
The composition of each layer should be 5 at% Rh (Rh is 45 to 55 at%, Fe is the remaining 55 to 45 at%).
Control the film thickness. The feature of this constitution is that, in the step of forming a thin film, in order to prevent the formation of the fcc phase and form a bcc structure, a composition having a bcc structure at the beginning of deposition, that is, Fe-50 at% Rh (both Rh and Fe are 50 at% )
The point is to form a layer having a composition richer in Fe than the composition. Fig. 2 shows the structure when a thin film is formed by sputtering by changing the composition. As can be seen from the figure, when the Rh composition is less than 35 at%, the bcc and the excess of 35 at% are exceeded when the Rh composition is less than 35 at%. Becomes the fcc structure. A composition of less than 35 at% having this bcc structure is used for the initial deposition layer. This configuration has two advantages. One is that the layer to be subsequently deposited tends to have the bcc structure, and the other is that even if the even layers after the second layer have the fcc structure, the substrate used when fcc is transformed into bcc during heat treatment is used. This is the point where the stress between the thin films is relaxed. After forming a thin film having these structures, heat treatment causes diffusion between layers, and Fe-45 to 55 at% R having a uniform bcc structure as shown in FIG.
The thin film 3 can be formed. Furthermore, claims 3 and 4 were invented for the purpose of stabilizing the bcc structure. First, if the temperature of the substrate is raised during the thin film deposition process, the bcc structure is easily obtained, and the growth of crystal grains is promoted to stabilize the antiferromagnetism. Fcc during thin film deposition
If the structure remains, fcc to bc during heat treatment
When transformed into c, a tensile stress is applied to the thin film, which promotes volume expansion and facilitates transformation.

Example 1 As shown in FIG. 3, a glass substrate 4
Sputtering was performed under the conditions of Ar gas pressure of 3 × 10 ⁻¹ Pa and 150 W, and Fe-20 at% Rh (Rh was 2
A layer of Fe-60 at% Rh (60 at% of Rh and 40 at% of Fe remaining) was alternately formed as a first layer 5 with 0 at% and 80 at% remaining Fe. The layer thicknesses are 200Å and 600Å, the number of layers is 3 each, and the total film thickness is 2400Å. The average Rh composition of the thin film in this state was about 50 at%. Further, in the X-ray diffraction measurement, it is a mixed phase of bcc and fcc. On the other hand, for comparison, when a thin film having a composition of Fe-50 at% Rh (both Rh and Fe is 50 at%) was manufactured to a film thickness of 2400 Å, it was fcc. Both thin films were annealed at 500 ° C. for 60 hours. As a result of measuring the temperature change of the magnetization with an applied magnetic field of 1 kG, as shown in FIG. 4, the thin film of the conventional method showed only a broad transition, but the thin film obtained by the manufacturing method of the present invention was almost equivalent to the bulk. A characteristic showing a sharp magnetization transition was obtained. In FIG. 4, the horizontal axis represents temperature and the vertical axis represents magnetization, and the characteristics according to the present invention and the conventional method are shown.

[Embodiment 2] The first layer is F
e, the second layer was Rh, and a film thickness of 300 Å and a laminated thin film of 5 layers each were formed. At this time, using a quartz substrate, the substrate temperature was changed to room temperature, 500 ° C., and 1000 ° C. As a result of X-ray diffraction, the higher the substrate temperature, the higher the bcc ratio, and the effect of heating the substrate was confirmed. Then 400
It was investigated how long the temperature was kept to show a sharp transition in the annealing at ℃. Substrate temperature is room temperature, 5
As the temperature rises to 00 ° C. and 1000 ° C., the annealing time required for complete transition is shortened to 50 hours and 30 hours, respectively.
It was 10 hours. Thus, it has been shown that if the substrate temperature is increased during thin film deposition, the targeted ordered alloy thin film can be easily obtained in a short annealing time.

Example 3 Kapton 100 μm was used as the substrate, and the film was formed by sputtering at the substrate temperature of room temperature. F
e-30at% Rh (Rh is 30at%, Fe is the remaining 70at%), Fe-70at% Rh (Rh is 70at%
%, Fe is the remaining 30 at%) and the film thickness is 50
0Å, a total of 2 layers were formed. As shown in FIG. 5, this thin film is bent to the substrate side together with (a) the substrate, and (b).
It was annealed at 600 ° C. for 40 hours in three states of bending to the thin film side and (c) no bending.
When the temperature change of magnetization was measured, it was found that the characteristics gradually improved in the order of B, C, and A as shown in FIG. It was shown that the best characteristics were obtained when the film was bent to the substrate side and tensile stress was applied to the film.

[0010]

As described above, when the manufacturing method of the present invention is used, even in a thin film, an antiferromagnetic property equivalent to that of a bulk-
The characteristic of the ferromagnetic transition can be obtained. Further, the increase of the substrate temperature and the application of the tensile stress during the heat treatment have the advantage that the characteristics equivalent to those of the bulk can be obtained in a short annealing time.

[Brief description of drawings]

1A and 1B show a manufacturing method of the present invention, in which FIG. 1A shows a structure during thin film formation, and FIG. 1B shows a state of a thin film after annealing.

FIG. 2 shows the composition dependence of the structure of a thin film obtained by forming a thin film by a conventional method.

FIG. 3 shows a structure of a thin film in Example 1.

FIG. 4 shows the temperature change of the magnetization of the thin film after annealing in Example 1.

FIG. 5 shows a form of annealing in Example 3,
(A), (b) and (c) show various shapes.

FIG. 6 shows temperature changes in magnetization of a thin film after annealing in Example 3.

FIG. 7 shows characteristics of a Fe-50 at% Rh alloy thin film produced by a conventional method.

[Explanation of symbols]

 1, 1a, 1b thin film 2 substrate 3 deposited thin film 4 glass substrate 5 Fe-20 at% Rh layer 6 Fe-60 at% Rh layer

Claims (4)

[Claims] 1. Rh is 0 to 35 at%, Fe is the remaining 1
Layer with a composition of 00 to 65 at% and Rh of 65 to 100 at
%, Fe are alternately deposited with the remaining 35 to 0 at% composition layer, and then heat treatment is performed to make the composition uniform in the thin film. Rh is 45 to 55 at% and Fe is 55 to 4 at%.
A method for producing a magnetic thin film, which comprises forming an alloy thin film containing 5 at% as a main component. 2. The initial deposition layer (first layer deposited on the substrate) has Rh of 0 to 35 at% and Fe of the remaining 100 to 65 at.
The method for producing a magnetic thin film according to claim 1, wherein the magnetic thin film is a layer having a% composition and has a crystal structure of a body-centered cubic lattice. 3. The substrate temperature is 100 ° C. to 1 during the deposition of the thin film.
The method for producing a magnetic thin film according to claim 1, wherein the method is maintained at 000 ° C. 4. The method for producing a magnetic thin film according to claim 1, wherein tensile stress is applied to the thin film while performing heat treatment for homogenizing the composition.