JPH07249517A - Temperature-sensitive magnetic thin film, its manufacture, and photodetecting type thin film temperature sensor - Google Patents

Abstract

PURPOSE:To provide techniques related to a temperature-sensitive magnetic thin film to which a designated temperature can be set easily with high accuracy and which can be formed through a simple process, the manufacturing method of the thin film, and a temperature sensor which utilizes the thin film and can accurately detect the temperature of a very small area by light from a remote area. CONSTITUTION:A temperature-sensitive magnetic thin film composed of a thin film 2 of an Fe-Rh alloy which has the crystal structure of cesium chloride and contains an element selected from among Pd, Pt, Ir, Ru, and Os by <=5atm% and a nonmagnetic thin film 3 which is formed on the thin film 2 and a partially varying thickness, a temperature-sensitive thin film manufacturing method by which the nonmagnetic thin film 3 is unevenly formed on the alloy thin film 2, and a photodetecting type thin film temperature sensor using the temperature-sensitive magnetic thin film. Therefore, the temperature-sensitive thin film which can be arbitrarily controlled to a designated temperature with accuracy can be easily manufactured and a manufacturing method by which the temperature-sensitive thin film can be manufactured through a simple process so that the sensitive temperature of the thin film can be easily corrected is provided. In addition, a thin film temperature sensor which can detect the temperature of a very small area by light from a remote place can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature-sensitive magnetic thin film, a method for producing the same, a photo-detecting thin film temperature sensor, and more specifically, a magnetic thin film applicable to various temperature sensors, temperature-sensitive actuators, etc., and a method for producing the same. , And a temperature sensor using a temperature-sensitive magnetic thin film.

[0002]

2. Description of the Related Art A so-called temperature-sensitive element is widely used, which utilizes the fact that magnetic properties such as magnetization, magnetic permeability, and coercive force of a magnetic material change rapidly with changes in temperature. A typical thermal reed switch is a combination of a ferrite core having a Curie temperature at a specified temperature, a permanent magnet, and a reed switch. This is a temperature control element that opens and closes the main circuit when the magnetic field applied to the reed switch changes due to a sudden decrease in the magnetic permeability of ferrite at a specified temperature.It is used for monitoring refrigerators, electronic pots, automobile engines, etc. Has been done. In addition to the use as the temperature sensor, the temperature-sensitive magnetic material is also applied to a conversion element for converting heat energy into electrical / mechanical energy, heating of a living body, and the like.

In recent years, demands for smaller and lighter electronic devices have been further heightened, and there are great expectations for sensors and actuators which are integrated on a silicon chip of an electronic circuit and used in a thin film form. Further, it is necessary to increase the accuracy with respect to temperature and set various designated temperatures.

[0004]

In order to meet these demands, the prior art has the following disadvantages. That is, one is that it is difficult to precisely control the specified temperature. To change the specified temperature, it is necessary to change the Curie point of the material. Curie point is a property peculiar to materials,
In order to change this, it is necessary to directly change the composition of the material. Mn-Cu-based ferrite, Fe-Ni-Cr-based alloy, Cu-Ni-based alloy and the like are often used materials, but depending on the composition ratio of each system or temperature, the alloy system itself is selected. , Have to change. Also, if the Curie point changes, the absolute value of the magnetization also changes at the same time, so it is necessary to design as a single item depending on the specified temperature and function.

The second problem is the difficulty in forming a thin film and processing. In forming a thin film, strict control of the above composition is further required. In addition, in order to integrate or combine materials of several specified temperatures, films of respective compositions have to be deposited separately, resulting in an enormous number of processes. Furthermore, in addition to these, when changing the design and the designated temperature, the previous thin film process cannot be applied, and it is impossible to change the designated value after element formation.

In addition to these inconveniences, in the medical field, the field requiring electromagnetic noise resistance, and the field requiring explosion proof, electric circuits, contacts, etc. are not used, and the temperature of a minute region is controlled by light. Although a remote temperature sensor for sensing is desired, there has been no such temperature sensor in the past.

In order to solve the above problems, the present invention uses a temperature-sensitive magnetic thin film which can set a designated temperature precisely and easily and can be easily formed into a thin film, a method for producing the same, and a method of using the thin film. It is an object of the present invention to provide a technique relating to a temperature sensor that remotely and accurately detects the temperature of a minute area by light.

[0008]

In order to solve the above problems, the temperature-sensitive magnetic thin film according to the present invention comprises Pd, Pt, Ir,
A non-magnetic thin film having a partially different thickness is deposited on a thin film of an Fe-Rh-based alloy having a cesium chloride crystal structure and containing 5 atm% or less of an element selected from Ru and Os. To do.

Further, the method for producing a temperature-sensitive magnetic thin film according to the present invention is an F-containing cesium chloride crystal structure containing 5 atm% or less of an element selected from Pd, Pt, Ir, Ru and Os.
An e-Rh-based alloy thin film is formed, and a non-magnetic thin film is non-uniformly deposited on the alloy thin film.

Further, the photo-detecting type thin film temperature sensor using the temperature-sensitive magnetic thin film according to the present invention is Pd, Pt, Ir, R.
Containing 5 atm% or less of an element selected from u and Os,
On a thin film of Fe-Rh-based alloy having a cesium chloride crystal structure,
A temperature-sensitive magnetic thin film formed by partially depositing non-magnetic thin films having different thicknesses, a means for injecting linearly polarized light into the temperature-sensitive magnetic thin film, and a reflected light from the temperature-sensitive magnetic thin film of the linearly polarized light. It is characterized by having a means for detecting and a magnetomotive force source for applying a magnetic field in a direction substantially parallel to the surface of the temperature-sensitive magnetic thin film.

One of the characteristics of the present invention is that Fe-Rh is not utilized by utilizing the change in magnetic characteristics at the Curie temperature.
This is the point of utilizing the magnetic phase transition in which the antiferromagnetism changes to the ferromagnetism in the thin film of a system alloy. An alloy with a composition in the vicinity of Fe-50 at% Rh (Fe-45 to 56 at% Rh composition) is C
It becomes an sCl type bcc ordered alloy. This ordered alloy is antiferromagnetic at low temperatures, but at 60 ° C to 100 ° C.
Changes to ferromagnetism at. In addition, 0 to 5 atomic% P
When d, Pt, Ir, Ru and Os are added to the alloy,
The transition temperature can be changed within the range of about 50 to 400 ° C. Since the magnetization of about 1000 G is discontinuously generated from the state where there is almost no magnetization at the transition temperature, there are many possible applications such as a temperature sensor and a thermosensitive actuator. We focus on utilizing the properties of this bulk in a thin film.

The second characteristic is that the above Fe-Rh alloy thin film is first formed on a substrate and then a nonmagnetic thin film is overcoated. This overcoat thin film is Fe
It is formed for the purpose of controlling the stress applied to the Rh thin film. The antiferromagnetic-ferromagnetic phase transition in Fe-Rh based alloys is stress sensitive and, in bulk, 100M
It is known that an increase in the phase transition point of 5 to 6 ° C. occurs per hydrostatic pressure (compressive stress) of Pa, but it is not practical to form an element under hydrostatic pressure. The inventors of the present invention used a non-magnetic thin film overcoating method, which is suitable for thin films.
The inventors have found that the transition point can be controlled by applying a dimensional stress, and arrived at the present invention.

The details will be described later in an embodiment.
Fig. 2 is a schematic diagram of the thin film structure, and Fig. 2 shows an example of changes in the behavior of the magnetization due to overcoating with respect to temperature. 1 in FIG.
Indicates a substrate, 2 indicates an Fe-Rh-based alloy thin film, and 3 indicates a non-magnetic overcoat thin film. Further, in FIG. 2, A shows the temperature change of the magnetization after the Fe51Rh49 alloy thin film having a thickness of 2000Å before the overcoat was formed by the sputtering method and annealed at 1000 ° C. It can be seen that, when SiO ₂ having a thickness of 2000 Å is formed on this thin film by the sputtering method, the phase transition temperature shifts to the high temperature side as in B. This is because compressive stress was applied to the Fe—Rh alloy thin film by the overcoat. The advantage of applying stress by this overcoat is that the magnitude of stress can be easily controlled by changing the film thickness of the overcoat. Furthermore, both the compressive stress and the tensile stress can be applied by changing the thin film forming conditions and the material for overcoating. Therefore, the magnetic phase transition point of the Fe-Rh-based alloy thin film formed first can be adjusted to the high temperature side or the low temperature side later, which is a very convenient manufacturing method. In addition, not only the entire thin film, but the change of the phase transition temperature only in a partial region of the thin film, or
It is possible to make the amount of change in magnetization with respect to temperature arbitrary.

When it is attempted to form temperature-sensitive switches that are turned on and off at a certain set temperature to form an element that switches at a plurality of different temperatures, according to the prior art, thin films having different compositions are separately formed. Had to be formed and integrated. According to the invention, the underlying Fe-R
It is easy to partially change the thickness of the non-magnetic thin film to be coated by using the same h-based alloy thin film. It is also possible to continuously change the film thickness of the non-magnetic thin film in a certain thin film region, that is, to form a film thickness gradient.

FIG. 3 is a schematic view of a structure when the overcoat thin film 3 has a film thickness gradient. If the overcoat has a film thickness gradient (distribution), the stress on the Fe-Rh-based alloy also has a gradient, and the transition temperature also has a distribution. Therefore, as the temperature increases, a partial phase transition occurs and the magnetization gradually increases. The effect is to increase. This makes it impossible with conventional materials. It is possible to manufacture a thin film material that exhibits a linear increase in magnetization with an increase in temperature.

By changing the transition temperature in the thin film portion by the above-mentioned method for producing the temperature-sensitive thin film, the temperature can be detected remotely by light in a minute region, which is very precise with respect to the temperature which could not be obtained in the past. A sensor can be created. FIG. 4 is a schematic diagram of the photo-detecting thin film temperature sensor of the present invention. 41 is Fe
A -Rh-based alloy thin film, 42 is a substrate, 43 is a permanent magnet, and a magnetic field is applied in parallel to the film surface through a yoke 44. On the other hand, the light from the light emitting element 45 is irradiated with the polarized light on the surface of the thin film 41 through the optical fiber 46 and the polarizer 47. The light reflected from the thin film 41 has its polarization plane rotated by the Kerr effect according to the magnitude of the magnetization, and then the light intensity is detected by the light receiving element 410 through the analyzer 48 and the fiber 49. When the Fe—Rh-based alloy is magnetized due to the temperature rise, the received light intensity changes correspondingly, so that the temperature can be remotely examined.

Irradiation and detection of light may be carried out in space without using a fiber. The feature of the present invention is that the thin film 4
1 and is divided into some portions 411 as shown in FIG. 5, and overcoats having different film thicknesses are formed. That is, the thin film portions 411 generate magnetization at different temperatures. The number of divisions and the temperature can be set within a specified range depending on the type of overcoat and the film thickness. As each division is increased, the accuracy with respect to temperature is improved. From the point of view of the process, the film thickness change in each divided region is easy by overcoating while shifting the mask. Further, even if it is not divided, the film thickness of the overcoat thin film has a gradient so that the magnetic phase transition can be continuously generated with respect to the temperature. In order to have the same function as the present sensor in the prior art, it was necessary to form the temperature sensitive material thin film having a different composition for each of the thin film portions 411 with high accuracy in terms of film thickness and composition. Obviously, it would be much easier.

Examples will be described below.

[0019]

Example 1 First, it was investigated how the stress of a non-magnetic overcoat thin film changed with the film thickness. A SiO ₂ thin film was formed on a Si substrate by changing the film thickness by sputtering under the conditions of Ar gas pressure of 3 × 10 ⁻¹ Pa and power of 300 W. Separately from this, ECR plasma CV is applied to the Si substrate.
According to the D method, Ar was used as a plasma forming gas and SiH ₄ / C ₂ H ₄ = 1.15 as a reaction gas at a gas flow rate of 5
A SiC thin film was formed under the conditions of 0 sccm and a substrate temperature of 700 ° C. The relationship between the film thickness of each thin film and the stress is shown in FIG. SiO ₂ formed by sputtering becomes compressive stress, and E
SiC formed by CR plasma CVD became tensile stress. 2.3 × 10 for each 1000 Å
^The stress was proportional to the film thickness at an increasing rate of ⁸ , 1.6 × 10 ⁸ Pa.

A Fe50Rh50 alloy thin film, that is, a thin film having a composition of Fe and Rh of 1: 1 is Ar gas pressure 3 × 1.
2 on a quartz substrate by sputtering at 0 ^-1 Pa and power of 150 W
The single layer thin film formed at 000Å and annealed at 1000 ° C showed a magnetic phase transition at 50 ° C. On top of this thin film, the SiO ₂ and SiC were respectively subjected to the same conditions as the stress measurement,
Overcoating was performed by changing the film thickness. As a result, F
The phase transition temperature of the e50Rh50 thin film was as shown in FIG. Reflecting the stress amount of the overcoat thin film alone, S
It can be seen that the transition point changes to the high temperature side with the compressive stress of the iO ₂ film and to the low temperature side with the tensile stress of the SiC film.
The change with film thickness is also shown in a linear relationship.

As described above, the stress at the time of depositing the overcoat can be utilized to control the phase transition temperature of the Fe-Rh-based thin film that has been previously formed. It can be seen that it can be changed to both the high temperature side and the high temperature side. Similar effects were confirmed for the SiN thin film formed by sputtering as shown in FIGS. 6 and 7. The overcoat thin film is not limited to the above thin film, and is not particularly limited as long as it is non-magnetic. 6 and 7, Δ is a graph showing results of SiC, ◯ is SiO ₂ and □ is a graph showing results of SiN.

[0022]

Example 2 Similar to Example 1, a sputtered and annealed Fe50Rh50 alloy thin film (film thickness 2000Å)
Then, SiO ₂ was formed with a structure as shown in FIG. 3 with a gradient in film thickness. The conditions for producing SiO ₂ are the same as in Example 1, but a shutter is provided between the substrate and the target, the shutter is moved at a constant speed, and the film thickness to be deposited is changed.
The film thickness gradient is from 0 to 4000 Å. FIG. 8 shows the change in magnetization with temperature after overcoating. By providing a film thickness gradient of the overcoat thin film, 4
A linear increase in magnetization was observed from 0 ° C to 100 ° C. If this linearity is used, it was impossible before.
It is possible to form an actuator or the like in which the temperature is monitored by detecting a continuous change in magnetization and the magnitude of force is controlled.

[0023]

Example 3 A thin film having a composition of Fe49Rh50Pd1 was formed by sputtering under the same conditions as in 2000Å Example 1 and annealed. This thin film had a magnetic phase transition at 40 ° C.
Six pieces of the same thin film were cut along with the substrate into 0.5 mm square pieces. Each has the same phase transition temperature as before cutting. The SiO ₂ overcoat was applied to each of these pieces by changing the film thickness. That is, the film thickness is 0 to 800Å
The film thickness was increased in steps. FIG. 9 shows the temperature change of each magnetization.

A photo-detection type temperature sensor having the above-mentioned structure was manufactured. In this figure, Fe
In this case, the Rh alloy thin film 41 was prepared by arranging the small pieces and fixing them on the slide glass. The permanent magnet 43 has NdFeB (B
r: 1.5 T), He was used for light irradiation without using a fiber.
It was detected by a photomul using Ne (wavelength 630 nm).
A heater and a thermocouple were arranged on the back surface of the magnetic film assembly corresponding to the probe of the sensor having the above-mentioned configuration, and the light intensity when the temperature was raised was measured.

As a result, as shown in FIG. 10, an optical output corresponding to the change in magnetization of each small piece was obtained, which showed its usefulness as a sensor. In this example, small pieces having different overcoat film thicknesses are assembled and combined with a magnet, but it goes without saying that the magnet and the probe can be integrally formed by a thin film process.

[0026]

As described above, by using the temperature-sensitive magnetic thin film and the method for producing the same according to the present invention, a temperature-sensitive magnetic thin film capable of controlling a designated temperature arbitrarily and precisely can be easily produced and thinned. The advantages are that it is possible to realize a method of manufacturing a temperature-sensitive magnetic thin film that can be easily processed and can correct the temperature-sensitive setting, and a thin-film temperature sensor that remotely detects the temperature of a minute region with light accurately.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an example of the present invention.

FIG. 2 is a diagram showing changes in magnetization-temperature characteristics due to overcoating.

FIG. 3 is a configuration diagram of another specific example of the present invention.

FIG. 4 is a schematic view of an example of a photo-detecting thin film detection sensor of the present invention.

FIG. 5 is an enlarged view of an alloy thin film.

FIG. 6 is a diagram showing the relationship between overcoat film thickness and stress in Example 1.

FIG. 7 is a graph showing the relationship between the overcoat film thickness and the magnetic phase transition temperature in Example 1.

FIG. 8 is a diagram showing temperature change of magnetization of a thin film after overcoating in Example 2.

FIG. 9 is a diagram showing temperature change of magnetization of a thin film after overcoating in Example 3.

FIG. 10 is a diagram showing a light detection intensity corresponding to a temperature change in the third embodiment.

[Explanation of symbols]

 1 Substrate 2 Fe-Rh-based alloy thin film 3 Overcoat thin film 41 Fe-Rh-based alloy thin film 42 Substrate 43 Permanent magnet 44 Yoke 45 Light emitting element 46 Optical fiber 47 Polarizer 48 Analyzer 49 Fiber 410 Light receiving element 411 Thin film portion

Claims (5)

[Claims] 1. A non-magnetic film having a partially different thickness on a thin film of an Fe-Rh-based alloy having a cesium chloride crystal structure containing 5 atm% or less of an element selected from Pd, Pt, Ir, Ru and Os. A temperature-sensitive magnetic thin film, which is formed by depositing a thin film of. 2. The non-magnetic thin film is made of SiO ₂ , SiC,
The temperature-sensitive magnetic thin film according to claim 1, which is one or more selected from SiN. 3. An Fe—Rh-based alloy thin film having a cesium chloride crystal structure containing an element selected from Pd, Pt, Ir, Ru and Os in an amount of 5 atm% or less, and a non-magnetic thin film on the alloy thin film. A method for producing a temperature-sensitive magnetic thin film, which comprises depositing non-uniformly. 4. The non-magnetic thin film is made of SiO ₂ , SiC,
The method for producing a temperature-sensitive magnetic thin film according to claim 3, wherein the temperature-sensitive magnetic thin film is at least one selected from SiN. 5. A non-magnetic film having a partially different thickness on a thin film of an Fe—Rh-based alloy having a cesium chloride crystal structure, containing 5 atm% or less of an element selected from Pd, Pt, Ir, Ru and Os. A temperature-sensitive magnetic thin film formed by depositing a thin film of, a means for injecting linearly polarized light into the temperature-sensitive magnetic thin film, and means for detecting reflected light from the temperature-sensitive magnetic thin film of the linearly polarized light,
A photodetection type thin film temperature sensor, comprising a magnetomotive force source for applying a magnetic field in a direction substantially parallel to the surface of the temperature-sensitive magnetic thin film.