JPH0499006A - Magnetostriction film for magnetostriction - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetostrictive thin film used in a magnetostrictive actuator that utilizes the magnetostrictive effect.

[Prior art] Today's development of microelectronics has led to the miniaturization and miniaturization of electrical elements, which is not only an issue of appearance such as realizing compact machines, but also improvements in functionality and quality that were previously impossible. The development of compact, high-output magnetostrictive actuators is required as an important issue in the miniaturization of such mechanisms.

Magnetostrictive actuators utilize the Joule effect, which causes the dimensions of a magnetic material to change when a magnetic field is applied to it, and conventional research has focused on alloys of rare earths and Fe as magnetic thin films. For example, SmFa
An example is hTbFe*.

[Problems to be Solved by the Invention] Characteristics required of the magnetostrictive film of the magnetostrictive actuator include: (1) A large saturation magnetostriction constant (λS) in order to increase the amount of displacement in response to magnetic changes and improve the characteristics.

■The operating magnetic field is small due to the miniaturization.

■The coefficient of thermal expansion (α) is small to reduce the influence of temperature changes.

It is necessary.

By the way, rt, which is known as the current magnetostrictive material alloy,
The magnetostriction constant of pes (R is a rare earth element) with respect to the magnetic field is
As shown in the magnetic field-magnetostriction constant characteristic curve in Figure 3, large values can be obtained;
230XI even with DyFe5, which requires
In order to obtain a saturation magnetostriction constant of O-'', a magnetic field of IKθ is required, and with this, it is not possible to downsize the device.For use in the micro area, at least a dozen θ is required, which is 200X10-'.
or higher magnetostriction constant is required. Furthermore, the thermal expansion coefficient of materials containing rare earth elements is as large as 10 to 20×10 −@/° C., and the above-mentioned requirements could not be met.

Therefore, a magnetostrictive material that satisfies the above-mentioned requirements and is easy to manufacture is desired.

[Means for Solving the Problems] The present inventor has conducted repeated research to solve the above problems, and has developed an invar type alloy having a low coefficient of thermal expansion using vacuum technology for the actuator material to a thickness of 2 μm or less at temperatures of 350°C or higher. By forming a thin film, or by forming a thin film with a thickness of 2 μm or less at less than 350°C and annealing it at 350°C or more,
A magnetostrictive film having an absolute value of the saturation magnetostriction constant exceeding 200×I01 was formed at 10 θ.

[The reason why the absolute value of the saturation magnetostriction constant can be significantly increased by making the magnetostrictive material thinner than in the case of bulk material is not clear, but magnetostriction changes when a magnetic field is applied to a magnetic material. This is a phenomenon in which the dimensions change, and the magnetization of Fe and C.

This is related to the arrangement of atoms such as Ni, so-called crystal structure, but even if the bulk material and thin film have the same crystal structure, the thin film has an overwhelmingly large amount of defects, and as a result, the average atomic The spacing is different, and it is thought that this difference in microstructure causes an increase in magnetostriction.

Note that if the temperature at the time of film formation is less than 350° C., the film will not be sufficiently crystallized and the coercive force will increase, making it necessary to increase the operating magnetic field.

In addition, by forming the thin film using vacuum technology, the coercive force of the film can be reduced, increasing the magnetostriction constant in a low magnetic field, and using an alloy with a small coefficient of thermal expansion as the thin film material, so small temperature changes in magnetostriction can be detected. Improves accuracy.

[Example code] Hereinafter, the present invention will be described in detail with reference to Examples.

Invar type alloys with a thermal expansion coefficient of 5xtO-@/”C or less, such as 32Ni-Fe, 34Ni-Fe
, 39Ni-Fe, and 63Fe-32Ni-5Co alloys, magnetostrictive thin films were prepared by vacuum evaporation, sputtering, and ion plating, and the saturation magnetostriction constants were measured.

For example, to show an example in which 39Ni-Fe is made into a thin film by sputtering, a quartz substrate is cleaned with Triclean and pure water, set in a two-electrode sputtering device, and the inside of a vacuum chamber is
After evacuation to below XIO-@Torr, the quartz substrate is
They were heated to different temperatures in the range of 50 to 600°C, and sx 1 (I'Torr) argon gas was introduced, and the target voltage was -400 V and the current was 0.
．． Sputtering was performed at 9A, and samples with various thicknesses were prepared by controlling the sputtering time.

As a result of measuring the saturation magnetostriction constant of the magnetic film obtained in this way, it was found that for the film produced at a substrate temperature of 350°C or higher, as shown by curve a in Figure 1, the film thickness was 15 μm up to 4 μm.
×lO−@, which was almost the same as the saturation magnetostriction constant of the bulk material, but when the film thickness became 3 μm or less, the saturation magnetostriction constant suddenly increased, and at 2 μm or less, the saturation magnetostriction constant was 200 × 10−
' or more values were obtained.

A magnetic field was applied to this magnetostrictive film with a thickness of 1.8 μm, and the relationship between the magnetostriction constant and the magnetic field was investigated. The results were as shown in Figure 2. It is saturated with

Furthermore, since the film produced at 300° C. or lower had a large coercive force, similar characteristics could be obtained by annealing it again in vacuum at 400° C. for 30 minutes.

As a result of experiments with other materials, similar trends were obtained.
The lOθ of each material with different film thickness is shown in the attached table.

The figure shows the results of measuring the magnetostriction constant of the film, and the thinner the film, the larger the value obtained.

Attached Table [Effects of the Invention] As described above, the present invention produces a magnetostrictive film for a magnetostrictive actuator by forming an invar alloy with an absolute value of thermal expansion coefficient of 5 x IO-"/°C or less at a temperature of 350°C or higher to a thickness of 2 μm or less. Since a vacuum thin film is formed, or a vacuum thin film is formed at a temperature below 350°C to a thickness of 2 μm or less and annealed at a temperature above 350°C, a large absolute value of the saturation magnetostriction constant can be obtained in a low magnetic field, and a large displacement can be obtained. It is inexpensive because it does not contain rare earth elements.Also, since it saturates with a small magnetic field, actuators using this magnetostrictive film can be made smaller.The coefficient of thermal expansion is small, and temperature compensation of the magnetostrictive film is required. This has the effect that a magnetostrictive actuator with high detection accuracy can be obtained without having to do so.

[Brief explanation of drawings]

FIG. 1 is a characteristic curve diagram showing the relationship between the film thickness and saturation magnetostriction constant of a magnetostrictive film according to an embodiment of the present invention, FIG. 2 is a characteristic curve diagram showing the relationship between the magnetostriction constant and the magnetic field, and FIG. FIG. 3 is a characteristic curve diagram showing the relationship between the magnetostriction constant and the magnetic field of the material. Figure 3 Film thickness (μm) Magnetic field H (KOe) Magnetic field COe)

Claims (1)

[Scope of Claims] 1. For use in a magnetostrictive actuator, characterized in that an invar alloy having an absolute value of thermal expansion coefficient of 5×10^-^6/°C or less is formed into a vacuum thin film of 2 μm or less at a temperature of 350°C or higher. Magnetostrictive film. 2. A magnetostrictive actuator characterized in that an invar alloy having an absolute value of thermal expansion coefficient of 5×10^-^6/°C or less is formed into a vacuum thin film of 2 μm or less in thickness at less than 350°C, and annealed at 350°C or more. magnetostrictive film. 3 The alloy is Ni-F containing 32 to 39 wt% Ni.
The magnetostrictive film for a magnetostrictive actuator according to claim 1 or 2, which is an e-based alloy. 4. The magnetostrictive film for a magnetostrictive actuator according to claim 1 or 2, wherein the vacuum thin film is formed by any one of a sputtering method, a vacuum evaporation method, and an ion plating method.