JP2003282992A - Ferromagnetic supermagnetostriction film and its thermal treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferromagnetic supermagnetostriction film wherein thickness is reduced while large magnetostriction constant is ensured. <P>SOLUTION: This ferromagnetic supermagnetostriction film is provided with a substrate, a base material film layer formed on the substrate, and a magnetic film layer formed on the base material film layer. The base material film layer is constituted of at least one kind out of tantalum and titanium. The magnetic film layer is composed of an Ni-Mn-Ca based alloy wherein the amount of Ni is at least 45 at.% and at most 58 at.%, the amount of Mn is at least 18 at.% and at most 28 at.%, and residual Ga and unavoidable impurities are contained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferromagnetic giant magnetostrictive film having a ferromagnetic property and a giant magnetostrictive property by forming a multilayer structure using a predetermined alloy. The present invention also relates to a heat treatment method for a ferromagnetic giant magnetostrictive film, which defines heat treatment conditions for manufacturing a ferromagnetic giant magnetostrictive film.

[0002]

2. Description of the Related Art A magnetic material having a magnetostrictive property has a property of causing displacement such as expansion and contraction when an external magnetic field is applied. A device to which this is applied is a displacement control or drive actuator, Td-Dy-Fe rare earth alloys and the like are known as materials used for torque sensors, ultrasonic vibrators, and the like.

Recently, in addition to the above materials, Fe--Pt alloys (Japanese Patent Laid-Open No. 11-269611) and Ni--Mn--Ga
A system alloy (Japanese Patent Laid-Open No. 10-259438) has been proposed. A magnetic field causes a crystal transformation, for example, from a tetragonal crystal structure to a cubic crystal structure, and therefore, a value much larger than that of a conventionally known magnetostrictive material can be exhibited.

[0004]

Ni-Mn-Ga alloys are mainly manufactured by powder metallurgy. However, considering the development of the material into a magnetic device, it is desirable to make the material thin and shape it, but there has been no report that the material was thinned while securing a large magnetostriction constant.

[0005]

To solve the above problems, a thin film is formed on a substrate from a base material such as a target by a vacuum film forming method or the like. After forming an underlayer for forming a film on a substrate, a magnetic layer of Ni—Mn—Ga based alloy is formed, and a large magnetostriction is induced by heat treatment in a vacuum or a non-oxidizing atmosphere. .

That is, the ferromagnetic giant magnetostrictive film of the present invention is a ferromagnetic giant magnetostrictive film comprising a substrate, a base film layer formed on the substrate, and a magnetic film layer formed on the base film layer. The underlying layer is tantalum (Ta), titanium (Ti)
And the magnetic film layer has a Ni content of 45 atomic% or more and 58 atomic% or less, a Mn content of 18 atomic% or more and 28 atomic% or less, and a balance Ga and unavoidable impurities. It is characterized by being a -Mn-Ga-based alloy. As a result, an excellent ferromagnetic giant magnetostrictive film is realized. The more preferable range of the amount of Ni and the amount of Mn is N
The i amount is 48 atom% or more and 55 atom% or less, and the Mn amount is 20 atom% or more and 26 atom% or less. Further, the magnetic film layer is preferably formed with a thickness of 100 nm or more and 3000 nm or less. If it is too thin, sufficient ferromagnetic properties and giant magnetostrictive properties cannot be obtained. Also, the thickness is 300
If it exceeds 0 nm, the residual stress of the thin film peels it off from the substrate, making it difficult to form an element. Here, the atomic% is a unit expressing the number of each element contained in the magnetic film layer or an arbitrary part of the magnetic film layer as a percentage, when the number of all the constituent atoms is 100. For example, when the amount of Ni is 45 atom%, when the surface of the magnetic film layer is quantitatively analyzed, the number of Ni atoms is 45 with respect to the total number of detected atoms (100%).
% Is equivalent to. When the unit of quantitative analysis of the magnetic film layer is mass% (= wt% or wt%), the Ni content of the magnetic film layer is 50 to 58 mass%.
Then, a Ni-Mn-Ga-based alloy having a Mn content of 21 to 23 mass% and a balance of Ga and unavoidable impurities is used.
The unavoidable impurities include the impurities used in the raw materials used for producing the magnetic film layer, such as Ni, Mn, Ga and their compounds defined by JIS. In addition, unavoidable impurities include gas elements (oxygen, nitrogen, hydrogen, etc.) that may be contained in the step of forming the magnetic film layer and its raw material. These unavoidable impurities are in the ppm order, that is, 10 ⁻⁴ atomic% or 10 ⁻⁴ mass.
It is desirable that the unit is% or less. More preferably less than the measurement limit of the composition analyzer or several pp
m or less. The substrate is a member that supports the magnetic film layer via the underlayer film layer. “On the substrate” refers to a state in which the base film layer and the magnetic film layer are formed on the surface of the substrate, and is not a term limiting the vertical relationship of the arrangement.

The ferromagnetic giant magnetostrictive film of the present invention has a composition of at least one of tantalum (Ta) and titanium (Ti) in the base film layer, and the film thickness of the base film layer is not particularly limited. However, a thick film thickness is not preferable in terms of production, and a thin film thickness that deteriorates the giant magnetostrictive characteristic of the device is not effective for manifesting the characteristics of the ferromagnetic magnetostrictive film formed thereon.
It is preferable that the thickness is in the range of m or more and 100 nm or less.
The underlayer has the effect of improving the crystal orientation and film quality of the Ni—Mn—Ga alloy ferromagnetic giant magnetostrictive film and improving the ferromagnetic properties and giant magnetostrictive properties. Further, a protective film made of the same material as that of the base film layer may be provided in order to improve mechanical breakdown and corrosion resistance of the ferromagnetic magnetostrictive film layer.

The heat treatment method for the ferromagnetic giant magnetostrictive film of the present invention is
After film formation, heat treatment is performed at 723 K or more and 973 K or less in a vacuum or a non-oxidizing atmosphere. The heat treatment in the atmosphere oxidizes the film and the desired characteristics are not exhibited. The heat treatment improves the crystallinity and realizes excellent ferromagnetic and giant magnetostrictive properties. If it is less than 723K, the above effect cannot be obtained. The upper limit temperature is not particularly limited, but the substrate material type is limited due to the heat resistant temperature of the substrate and the like, which is not preferable in production. Above 773K and below 973K, particularly excellent ferromagnetic properties and giant magnetostrictive properties are obtained. It is characterized by excellent ferromagnetic properties and giant magnetostriction properties at heat treatment temperatures of 773 K or higher and 973 K or lower, which are low temperatures not used in conventional bulk materials. More specifically, in the method for heat treating a ferromagnetic giant magnetostrictive film of the present invention, a base film layer is formed on a substrate, the Ni amount is 45 atom% or more and 58 atom% or less, and the Mn content is on the base film layer. Forming a magnetic film layer of a Ni-Mn-Ga-based alloy having a balance of Ga and inevitable impurities of 18 atomic% or more and 28 atomic% or less, and then performing heat treatment at 723 K or more and 973 K or less in a vacuum or a non-oxidizing atmosphere It is characterized by applying.

The Ni-Mn-Ga-based alloy ferromagnetic giant magnetostrictive film of the present invention has an a-axis lattice constant obtained by X-ray diffraction smaller than 0.583 of the conventional bulk material and excellent at 0.580 nm or less. The ferromagnetic property and the giant magnetostrictive property are realized. Further, when the lattice constant ratio c / a of the a-axis and the c-axis is 0.95 or less, particularly excellent ferromagnetic properties and giant magnetostrictive properties can be obtained. In the region exceeding 0.95, the desired giant magnetostrictive property is not sufficiently expressed. More specifically, the ferromagnetic giant magnetostrictive film of the present invention is a ferromagnetic giant magnetostrictive film including a substrate, a base film layer formed on the substrate, and a magnetic film layer formed on the base film layer. And the magnetic film layer is a Ni-Mn-Ga-based alloy,
The a-axis lattice constant of the Mn-Ga alloy is 0.58 nm or less, and the a-axis to c-axis lattice constant ratio c / a is 0.95.
It is characterized by the following. In c / a, a is a
It is the lattice constant of the axis, and c corresponds to the lattice constant of the c-axis.

In the present invention, the base film layer and the magnetic film layer are formed on the substrate one by one, but a plurality of base film layers and magnetic film layers may be alternately stacked. The material of the substrate may be selected in consideration of the coefficient of thermal expansion and the heat resistant temperature.

A sputtering method, an ion beam method or the like can be used for producing the ferromagnetic giant magnetostrictive film of the present invention.

The present invention can constitute an actuator comprising a ferromagnetic giant magnetostrictive film according to any one of the above-mentioned present invention and means (for example, a conductor or a coil) for applying a magnetic field to the ferromagnetic giant magnetostrictive film. Further, the substrate can be a cantilever, a cantilever beam or a double-supported beam, and the substrate can be displaced by applying a magnetic field to the ferromagnetic giant magnetostrictive film. In particular, MEMS (Micro E
It is desirable to apply the ferromagnetic giant magnetostrictive film according to the present invention to a micro mechanical system) or a micro actuator.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the ferromagnetic giant magnetostrictive film of the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. (Example 1) A Si substrate having one surface polished and a surface having a 1 μm oxidation treatment and a glass substrate having both surfaces polished were placed in a sputtering apparatus, and a Ta target was used for a base film layer.
53 atomic% Ni-2 1.5 atomic% Mn-2 in the magnetic film layer
A 5.5 atom% Ga target was set in the sputtering apparatus. After exhausting the inside of the apparatus to 3 × 10 ⁻⁵ Pa or less, A
Flow r gas at 100 ml / s and set the pressure inside the device at 0.35P
Keep the temperature at a and discharge at 200 W to discharge the substrate for 60
s (60 seconds). The discharge output was set to 150 W, and the Ta target used for the underlayer film was discharged to form a Ta underlayer film of 50 nm on the substrate. After that, 53 atomic% Ni-
A 21.5 atom% Mn-25.5 atom% Ga target was discharged to form a magnetic film layer with a thickness of 200 nm to obtain a ferromagnetic giant magnetostrictive film (Invention Product 1-1) of the invention. In order to investigate the influence of the film thickness of the magnetic film layer, a ferromagnetic giant magnetostrictive film having a magnetic film layer of 500 nm (invention product 1-2) and a ferromagnetic giant magnetostrictive film having a magnetic film layer of 1000 nm (invention product 1-3). Ferromagnetic giant magnetostrictive films (invention products 1-4) having magnetic film layers of 3000 nm were manufactured. The unit of gas flow rate, ml / s, is to flow 10 ⁻⁶ cubic meters of gas per second (10 ⁻⁶ (m ³ / s)).
Equivalent to.

In order to investigate the influence of the heat treatment temperature, the invention product 1-1 was subjected to an experiment using a vacuum heat treatment furnace at a predetermined heat treatment temperature of 573 to 1073K.
Heat treatment time is 1 hour and 6.7x to prevent sample oxidation.
Heat treatment is performed in a vacuum of 10 ⁻³ Pa or less, and the invention product 1-
2 to invention products 1-4, heat treatment temperature is 873K,
Heat treatment time is 1 hour, 6.7 × 10 ^-3 P to prevent oxidation
Heat treatment was performed in a vacuum of a or less to evaluate the characteristics.

Comparative Example 1 A comparative experiment was conducted to compare the influence of the film thickness of the magnetic film layer. S as in the first embodiment
Using an i substrate and a glass substrate, the i target was placed in a sputtering apparatus, a Ta target was used for the underlying film layer, and 54 atomic% Ni-21 atomic% Mn-25 atomic% Ga similar to that in Example 1 was used for the magnetic film layer.
The target was set in the sputtering device. 3 × inside the device
After exhausting to 10 ⁻⁵ Pa or less, Ar gas is set to 100 m
The flow rate was 1 / s, the pressure inside the apparatus was maintained at 0.35 Pa, the discharge was performed at a discharge output of 200 W, and the substrate was washed for 60 s (60 seconds). Ta used for the base film layer by setting the discharge output to 150 W
The target is discharged and the Ta underlayer is 50 nm on the substrate.
A film was formed. After that, 54 atomic% Ni-21 atomic% Mn-
Discharge to a 25 atomic% Ga target and apply a magnetic layer of 50
A ferromagnetic giant magnetostrictive film with a thickness of 00 nm for comparison (Comparative product 1)
Got

The heat treatment conditions were the same as in Example 1, such that the heat treatment temperature was 873 K, the heat treatment time was 1 hour, and the heat treatment was performed in a vacuum of 6.7 × 10 ⁻³ Pa or less to prevent oxidation, and the characteristics were evaluated. did.

The magnetic properties of the invention product 1-1 after heat treatment at 573 to 1073K were evaluated by a VSM (vibrating magnetometer) at a measurement magnetic field of 200 kA / m, and FIG. 1 shows the relation between heat treatment temperature and saturation magnetization. Saturation magnetization cannot be obtained after film formation, but saturation magnetization is obtained by performing heat treatment.
A saturation magnetization of 0.2 T or more was obtained at ˜973 K. Further, it can be seen that a saturation magnetization of 0.35 T or more is obtained at 773 to 923K.

Further, by using a magnetostriction measuring device, a measuring magnetic field 12
Magnetostriction was evaluated at 0 kA / m, and FIG. 2 shows the relationship between heat treatment temperature and magnetostriction. The magnetostriction value is improved by heat treatment,
It is understood that a magnetostriction of 4 × 10 ⁻⁶ or more can be obtained at 73 to 923K.

FIG. 3 shows the relationship between the film thickness and the film stress of the magnetic film layer after the heat treatment at 327K. It can be seen that the film stress increases as the film thickness of the magnetic film layer increases. In Comparative product 1 in which the magnetic film layer was formed to a thickness of 5000 nm, the film stress was higher than the adhesive force of the film after the heat treatment at 873K, and film peeling occurred.

(Example 2) Using the Si wafer used in Example 1 and a glass substrate whose both surfaces were polished, the glass substrate was placed in a sputtering apparatus, and a Ta target was used for the underlayer and a magnetic layer was used for the magnetic film layer.
Atomic% Ni-21 atomic% Mn-25 atomic% Ga and 52 atomic% Ni-23 atomic% Mn-25 atomic% Ga targets were placed in the sputtering apparatus, respectively. 3 × 1 inside the device
0 ^-5 Pa was evacuated to below, the Ar gas 100ml /
s flow, keep the pressure in the device at 0.35Pa, discharge output 2
The substrate was washed at 60 W for 60 seconds. Discharge output 1
It was set to 50 W and the Ta target used for the base film layer was discharged to form a Ta base film layer of 50 nm on the substrate. After that, 54 atomic% Ni-21 atomic% Mn-25 atomic% Ga
The target was discharged to form a magnetic film layer with a thickness of 200 nm to obtain a ferromagnetic giant magnetostrictive film of the present invention (Invention Product 2-1). Also,
A ferromagnetic giant magnetostrictive film (invention product 2-2) having a magnetic film layer having a composition of 52 atomic% Ni-23 atomic% Mn-25 atomic% Ga was manufactured.

The heat treatment temperature is 873K.
Heat treatment time is 1 hour, 6.7 × 10 ^-3 P to prevent oxidation
Heat treatment was performed in a vacuum of a or less to evaluate the characteristics.

Comparative Example 2 A comparative experiment was conducted to compare the effect of the film composition of the magnetic film layer. As in Example 2, a Si substrate and a glass substrate were used and placed in a sputtering apparatus,
Ta target for underlayer and 44 atom% for magnetic layer
A Ni-35 atom% Mn-21 atom% Ga target was placed in the sputtering apparatus. After exhausting the inside of the apparatus to 3 × 10 ⁻⁵ Pa or less, Ar gas was caused to flow at 100 ml / s, the pressure inside the apparatus was maintained at 0.35 Pa, and discharge was performed at a discharge output of 200 W to wash the substrate for 60 seconds. The discharge output was set to 150 W, and the Ta target used for the underlayer film was discharged to form a Ta underlayer film of 50 nm on the substrate. Then, it was discharged to a target of 44 atomic% Ni-35 atomic% Mn-21 atomic% Ga to form a magnetic film layer with a thickness of 200 nm to obtain a comparative ferromagnetic giant magnetostrictive film (comparative product 2).

The heat treatment conditions were the same as in Example 2 except that the heat treatment temperature was 873 K, the heat treatment time was 1 hour, and the heat treatment was performed in a vacuum of 6.7 × 10 ⁻³ Pa or less to prevent oxidation, and the characteristics were evaluated. did.

FIG. 4 shows the X-ray diffraction results at room temperature of the invention product 2-1 and the invention product 2-2 produced in Example 2 and Comparative Example 2. From FIG. 4, a diffraction peak of the (220) plane of Ni-Mn-Ga appeared in the invention product and the comparative product at 2θ of around 43 °. When the lattice constants of the respective a-axes were measured, the invention product 2-1 and the invention product 2-2 were 0.5786 nm and 0.580.
It is 0 nm. On the other hand, Comparative product 2 has a large value of 0.5816 nm. At this time, as a result of measuring the magnetostriction with a measurement magnetic field of 120 kA / m, the magnetostriction value of the invention product 2-1 and the invention product 2-2 was 9.
It was found that 0 × 10 ⁻⁶ and 8.5 × 10 ⁻⁶ were high, and Comparative product 2 was low, 3.0 × 10 ⁻⁶ .

(Example 3) Using the Si wafer used in Example 2 and a glass substrate having both sides polished, the glass substrate was placed in a sputtering apparatus, a Ta target was used for the underlayer and 51 atomic% Ni was used.
-25 atom% Mn-24 atom% Ga, 48.5 atom% N
An i-26 atomic% Mn-25.5 atomic% Ga target was placed in each sputtering apparatus. 3 × 10 inside the device
After exhausting to ^-5 Pa or less, Ar gas 100 ml / s
Flow to maintain the pressure inside the device at 0.35 Pa, and discharge output 20
The discharge was performed at 0 W and the substrate was washed for 60 seconds. Discharge output 15
It was set to 0 W and the Ta target used for the base film layer was discharged to form a Ta base film layer of 50 nm on the substrate. After that, 51 atomic% Ni-25 atomic% Mn-24 atomic% Ga
The target was discharged to form a magnetic film layer with a thickness of 200 nm to obtain a ferromagnetic giant magnetostrictive film (invention product 3-1) of the present invention. Also,
48.5 atom% Ni-26 atom% Mn-25.5 atom%
Ferromagnetic giant magnetostrictive film having a magnetic film layer of Ga composition (Invention product 3
-2) were produced respectively.

The heat treatment temperature is 873K,
Heat treatment time is 1 hour, 6.7 × 10 ^-3 P to prevent oxidation
Heat treatment was performed in a vacuum of a or less to evaluate the characteristics.

Comparative Example 3 A comparative experiment was conducted to compare the effect of the film composition of the magnetic film layer. As in Example 3, a Si substrate and a glass substrate were used and placed in a sputtering apparatus,
Ta target for underlayer and 56 atom% for magnetic layer
Ni-15 atomic% Mn-29 atomic% Ga was installed in the sputtering apparatus. After exhausting the inside of the apparatus to 3 × 10 ⁻⁵ Pa or less, Ar gas was caused to flow at 100 ml / s, the pressure inside the apparatus was maintained at 0.35 Pa, and discharge was performed at a discharge output of 200 W to wash the substrate for 60 seconds. The discharge output was set to 150 W, and the Ta target used for the underlayer film was discharged to form a Ta underlayer film of 50 nm on the substrate. After that, 56 atomic% Ni-
A 15 atomic% Mn-29 atomic% Ga target was discharged to form a magnetic film layer with a thickness of 200 nm to obtain a ferromagnetic giant magnetostrictive film for comparison (comparative product 3).

The heat treatment conditions were the same as in Example 3, such that the heat treatment temperature was 873 K, the heat treatment time was 1 hour, and the heat treatment was performed in a vacuum of 6.7 × 10 ⁻³ Pa or less to prevent oxidation, and the characteristics were evaluated. did.

FIG. 5 shows the X-ray diffraction results at room temperature of the invention product 3-1, invention product 3-2 and comparison product 3 produced in Example 3 and Comparative Example 3. As shown in FIG. 5, the diffraction peak of the (220) plane appears on the low angle side of Ni-Mn-Ga and the diffraction peak of the (202) plane appears on the wide angle side in both of the invention product and the comparative product when 2θ is around 43 °. It can be seen that it has a crystal structure. When the lattice constant ratios c / a of the a-axis and the c-axis are measured, the invention product 3-1 and the invention product 3-2 are 0.950 and 0.945. On the other hand, Comparative product 3 is 0.962, which is large. At this time, the measurement magnetic field 12
As a result of measuring the magnetostriction at 0 kA / m, the magnetostriction values of the invention product 3-1 and the invention product 3-2 are 7.5 × 10 ⁻⁶ and 6.0 × 10.
It was found that the value was as high as ⁻⁶ and the value for Comparative product 3 was as low as 1.0 × 10 ⁻⁶ .

[0030]

As described above, according to the ferromagnetic giant magnetostrictive film of the present invention, a Ni-Mn-Ga-based alloy is formed in a predetermined structure,
By heat-treating at a predetermined temperature, an excellent ferromagnetic giant magnetostrictive film having ferromagnetic properties and giant magnetostrictive properties can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing the heat treatment temperature dependence of the saturation magnetization of the ferromagnetic giant magnetostrictive film of the present invention.

FIG. 2 is a diagram showing the heat treatment temperature dependence of the magnetostriction of the ferromagnetic giant magnetostrictive film of the present invention.

FIG. 3 is a diagram showing the film thickness dependence of the film stress of the ferromagnetic giant magnetostrictive film of the present invention.

FIG. 4 is an X-ray diffraction diagram when the film composition of the ferromagnetic giant magnetostrictive film is changed and a heat treatment is performed at 873K.

FIG. 5 is an X-ray diffraction diagram when a film composition of a ferromagnetic giant magnetostrictive film is changed and a heat treatment is performed at 873K.

Claims (4)

[Claims] 1. A ferromagnetic giant magnetostrictive film comprising a substrate, a base film layer formed on the substrate, and a magnetic film layer formed on the base film layer, wherein the base film layer is tantalum, The magnetic film layer is composed of at least one kind of titanium, and the magnetic film layer has a Ni content of 45 atomic% or more and 58 atomic% or less and Mn.
A ferromagnetic giant magnetostrictive film, characterized in that the amount is 18 atomic% or more and 28 atomic% or less and is a Ni-Mn-Ga based alloy having the balance Ga and unavoidable impurities. 2. The magnetic film layer has a thickness of 100 nm or more and 30 or more.
The ferromagnetic giant magnetostrictive film according to claim 1, which is formed with a thickness of 00 nm or less. 3. A ferromagnetic giant magnetostrictive film comprising a substrate, a base film layer formed on the substrate, and a magnetic film layer formed on the base film layer, wherein the magnetic film layer is Ni-- Mn-G
It is an a-based alloy, the a-axis lattice constant of the Ni-Mn-Ga-based alloy is 0.58 nm or less, and the lattice constant ratio c / a of the a-axis and the c-axis is 0.95 or less. Characteristic ferromagnetic giant magnetostrictive film. 4. A base film layer is formed on a substrate, and the amount of Ni is 45 atom% or more and 58 atom% or less on the base film layer,
When the amount of Mn is 18 atomic% or more and 28 atomic% or less, the balance Ga
And a magnetic film layer of a Ni-Mn-Ga-based alloy having unavoidable impurities, and thereafter heat-treated at 723 K or more and 973 K or less in a vacuum or a non-oxidizing atmosphere. Heat treatment method.