KR20070030761A - R-Fe-B BASED THIN FILM MAGNET AND METHOD FOR PREPARATION THEREOF - Google Patents

Abstract

In the R-Fe-B type alloy containing 28-45 mass% of R elements (wherein R is one kind or two or more kinds of rare earth lanthanide elements), the grain size is 0.5 to 30 µm. An R-Fe-B thin film magnet having a complex structure with an R ₂ Fe ₁₄ B crystal and a grain boundary phase in which R elements are enriched at the boundary of the crystal. Magnetization of the thin film magnet was improved. In the physical film formation and / or subsequent heat treatment, the R-Fe-B-based thin film magnet can be produced by forming grain boundaries and enriched grains of R elements as it is heated to 700 to 1200 ° C. have.

R-Fe-B type, thin film magnet, magnetization, grain size

Description

R-Fe-B thin film magnet and its manufacturing method {R-Fe-B BASED THIN FILM MAGNET AND METHOD FOR PREPARATION THEREOF}

The present invention relates to a high-performance thin film magnet suitable for a micro machine, a sensor, and a small medical / information device, and a manufacturing method thereof.

Nd-Fe-B-based rare earth sintered magnets, mainly Nd as the rare earth element R, have high magnetic properties and are used in various fields besides VCM (Voice Coil Motor) and MRI (Magnetic Tomography). . These magnets have a size of several to several tens of millimeters on one side, but in a vibration motor for mobile phones, a cylindrical magnet having an outer diameter of 3 mm or less is used, and a smaller magnet is required in the field of micromachines and sensors. For example, a flat plate magnet having a thickness of 1 mm or less is produced by cutting or polishing a large block of sintered body in advance, but it is difficult to obtain a magnet of 0.5 mm or less due to problems of magnet strength and productivity.

On the other hand, thin film magnets having a small dimension can be manufactured by physical film forming methods such as sputtering and laser deposition, and the maximum energy energy of 200 kJ / m 3 or more has been reported as magnetic properties (eg For example, Non-Patent Document 1, Patent Document 1). According to these production methods, a magnetic alloy component is deposited on a substrate or a shaft in a vacuum or reduced pressure space, subjected to heat treatment, and the various conditions are controlled appropriately so that a high-performance film of about 200 kJ / m 3 is relatively simple compared with the sintering method. You can get it.

As a general example, the thickness of a thin film magnet formed on a substrate such as a flat plate or a shaft is in the range of several tens to several tens of micrometers, and is often from one tenth to one hundredth of the diameter of the four sides and the shaft of the flat plate. When the thin film is magnetized in the direction perpendicular to the flat surface or the circumferential surface of the thin film, the anti-magnetic field becomes very large and sufficient magnetization cannot be achieved, which makes it difficult to derive the original magnetic properties of the thin film magnet. . It is generally known that the size of the diamagnetic field depends on the ratio of the magnetization direction to the perpendicular direction thereof, and the larger the dimension of the magnetization direction (= film thickness direction) becomes.

On the other hand, from a viewpoint different from the problem of the above dimensional ratio, if a magnetic material that is easy to magnetize can be produced, it is possible to easily derive the characteristics of the thin film magnet, which is advantageous in the production of various application devices. Conventional Nd-Fe-B-based thin film magnets generally deposit 0.3 占 퐉 corresponding to a single magnetic domain particle diameter by depositing a magnetic component on a substrate in an atomic or ionized state and then subjecting it to heat treatment. is employed a method of generating a Nd ₂ Fe ₁₄ B crystal grains of less than (Patent Document 2, 3).

At this time, generally, it is a usual means to suppress the crystal grains and obtain desired magnetic properties (for example, Patent Document 4). However, few documents discuss crystal grain size and magnetization. In addition, when the crystal grains are grown to 0.3 µm or more, the inside of each crystal grain becomes a multi-sphere structure, and the coercive force decreases.

As a reference for the magnetomagnetic support, Fig. 1 (a) shows the supermagnetization curve and the potato curve of the general sintered magnet, and Fig. 1 (b) shows the supermagnetization curve and the potato curve of the thin film magnet of the conventional example. As can be clearly seen from Fig. 1 (a), when the sintered magnet is subjected to a magnetic field, the magnetization rises rapidly and shows sufficiently high magnetic properties even at a low magnetic field of about 0.4 MA / m.

On the other hand, in the case of the thin film magnet of the conventional example of FIG. 1 (b), the magnetization gradually increases at the origin, and no saturation tendency appears even in a magnetic field of 1.2 MA / m. This difference in magnetism is assumed to be due to the fact that the sintered magnet has a nucleus-type coercive force mechanism, and the thin film magnet of the prior art relies on the coercive force generator of the terminal sphere particle type.

Non Patent Literature 1: Journal of the Korean Society for Applied Magnetics, Vol. 27, No. 10, p. 1007, 2003

Patent Document 1: Japanese Patent Application Laid-Open No. 8-83713

Patent Document 2: Japanese Patent Application Laid-Open No. 11-288812

Patent Document 3: Japanese Patent Application Laid-Open No. 2001-217124

Patent Document 4: Japanese Patent Application Laid-Open No. 2001-274016

(Initiation of invention)

(Problem that invention tries to solve)

An object of the present invention is to improve magnetization of a thin film magnet.

(Means for solving the invention)

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching a composition and a crystal structure for the purpose of improving the magnetization of a thin film magnet, the present inventors succeeded in producing the thin film magnet which has the same nucleation-type coercive mechanism as a sintered magnet.

In other words, the present invention provides a (1) R-Fe-B-based alloy containing 28 to 45% by mass of the R element (wherein R is one kind or two or more kinds of rare earth lanthanide elements) physically formed In the R ₂ Fe ₁₄ B crystal having a grain size of 0.5 to 30 µm and a grain structure in which the R element is enriched at the boundary of the crystal; B type thin film magnet.

The present invention is also characterized in that (2) the C axis, which is an axis of easy magnetization of R ₂ Fe ₁₄ B crystals, is non-oriented or is oriented substantially perpendicular to the film surface. R-Fe-B thin film magnet of 1).

Moreover, this invention is (3) R-Fe-B type thin film magnet of said (1) or (2) whose film thickness is 0.2-400 micrometers.

Furthermore, the present invention provides (4) grain boundary phase in which grain growth and R element are enriched by heating to 700-1200 ° C. during the physical deposition of R-Fe-B alloy and / or subsequent heat treatment. The method for producing the R-Fe-B-based thin film magnet according to any one of (1) to (3), wherein the formation of the film is performed.

In the case where the crystal structure of the Nd-Fe-B-based thin film magnet is almost composed of R ₂ Fe ₁₄ B crystals and the grain size thereof is smaller than the terminal sphere particle size corresponding to 0.3 μm, the magnetization direction of each crystal grain is determined by the magnetic field. Since it rotates slowly with respect to size, it is difficult to make enough magnetization as shown by the supermagnetization curve of the thin film magnet of the conventional example of FIG.

In addition, since thin film magnets are often applied to minute devices, it is practically difficult to apply a large magnetic field to minute areas.

On the other hand, in the case of the magnet of the present invention, which is composed of a composite structure of R ₂ Fe ₁₄ B crystal whose crystal structure is larger than the particle size of the terminal sphere and the grain boundary phase of which R element is enriched, the magnetic field is described later. As can be estimated from the supermagnetization curve of the sample 2 of FIG. 3, a plurality of magnetic domains present in each crystal grain remove the adjacent magnetic domain walls and move in a small magnetic field. Sufficient magnetization similar to the sintered magnet is produced toward the surface. This difficulty and ease of magnetization is presumably because the thin film magnet of the prior art has a coercive force generating mechanism of the terminal sphere particle shape, while the thin film magnet of the present invention has a coercive force generating mechanism of the nucleus generation type.

(The best mode for carrying out the invention)

(Alloy system, crystal structure)

The thin film magnet to be used in the present invention is composed of an R-Fe-B-based alloy when the rare earth element is represented by R, and an Nd-Fe-B-based alloy is generally used. In actual alloy production, in order to improve the coercive force of a thin film magnet, addition of Pr, Dy, Tb, etc., as well as Nd as a R element, inexpensive Ce, etc. is performed. In addition, various transition metal elements such as Ti, V, Mo, and Cu, P, Si, and Al are added to appropriately control the crystallization temperature and grain size of the deposited alloy, or Co, Pd, and Pt are used to improve corrosion resistance. It is usual to add various transition metal elements such as these.

The total amount of rare earth elements R such as Nd, Pr, Dy, and Tb in the alloy is ₂₈ to 45 mass to form a composite structure of R ₂ Fe ₁₄ B crystals and grain boundary phase enriched by R elements. It is essential to set it as%, and it is more preferable to set it as 32-40 mass%. I.e., R element content in the alloy is required to be larger than the R ₂ Fe ₁₄ B composition. The grain boundary phase enriched by the R element contains at least 50 mass% of the R element and contains a small amount of Fe or other additives. It is assumed to be a phase similar to the RO ₂ or R ₂ O ₃ type oxide.

The amount of Nd in the stoichiometric composition of Nd ₂ Fe ₁₄ B using Nd as a representative example is 26.7% by mass, and in order to coexist a small amount of the grain boundary phase enriched by Nd, the element R in the alloy It is necessary to be at least 28 mass%. On the other hand, when the amount of R element increases, the ratio of grain boundary phase in the alloy increases, and the coercive force is improved, but the ratio of Nd ₂ Fe ₁₄ B crystals decreases, thereby reducing the magnetization remarkably, and thus high magnetic properties cannot be obtained. It is necessary to be 45 mass% or less.

As for the relationship between the Nd ₂ Fe ₁₄ B crystal and the Nd enrichment grain boundary in the alloy, the grain boundary of the latter is almost enclosed around the former grain as in the case of the sintered magnet. Cheap organization. When the ratio of the grain boundary is small, the thickness is as thin as about 10 nm, and since the grain is broken in part, it tends to be highly magnetized by low coercive force. It becomes several hundred nm-1 micrometer, and there exists a tendency for low magnetization with high coercive force.

As for the grain size, in general, the average size of the crystals is cut in many directions, but when the film thickness is thin, the average size of the crystals observed in the film surface is determined. I express it with a particle size. Specifically, the measurement method is observed by SEM (scanning electron microscope) or a high magnification metal microscope of a sample in which the Nd-Fe-B-based thin film formed on a flat substrate or on an axis surface is etched with alcohol nitrate. One line was drawn on the obtained image photograph, and the average value was computed by length measuring the grain size which is 200 micrometers long on the line, and made it the crystal grain size.

The particle size of the Nd ₂ Fe ₁₄ B crystal needs to be 0.5 to 30 µm, more preferably 3 to 15 µm, since the magnetization of the nucleus-type coercive mechanism increases rapidly with respect to the magnetic field. As described above, if the diameter is less than 0.5 µm, the size of the terminal sphere particle size is close, and the rise of the supermagnetization curve is gentle, making magnetization difficult. On the other hand, when the particle diameter exceeds 30 mu m, the number of magnetic domains present in one crystal becomes excessive, the magnetization is easily reversed, and the coercive force required even when a grain boundary phase is formed cannot be obtained.

In the R-Fe-B-based thin film magnet of the present invention, the C-axis, which is an axis of easy magnetization of the R ₂ Fe ₁₄ B crystal, is non-oriented or oriented substantially perpendicular to the film surface. In the present invention, magnetization is improved basically regardless of the orientation of the C axis. However, when the C axis is parallel to the membrane surface, the effect of the diamagnetic field is small and the effect of improving magnetization becomes small.

(Film thickness, film formation method, substrate)

When the thickness of the Nd-Fe-B-based film is in the range of 0.2 to 400 µm, the effects of the present invention can be sufficiently exhibited. If the particle size is smaller than 0.2 µm, the volume of Nd ₂ Fe ₁₄ B grains decreases, and even though a complex structure with the Nd enrichment boundary phase is formed, the grain shape of the terminal sphere is still dominant, resulting in good magnetization. I can't. On the other hand, when it exceeds 400 micrometers, the size and orientation of a crystal | crystallization will become large in the lower part and upper part of a film | membrane, and residual magnetization will fall. In addition, it is necessary to operate for a long time of about 1 day or more, and a thickness of more than 400 μm can be obtained relatively easily by a method of cutting and polishing a sintered magnet, so that the film thickness of more than 400 μm is the upper limit of the film thickness. Is 400 µm.

As the film forming method, various physical film forming methods such as plating, in which an alloy is deposited in a liquid, coating or spraying fine alloy powder particles or coating, or CVD, deposition, sputtering, ion plating, and laser deposition can be used. Can be. In particular, the physical film forming method is most preferable as the film forming method of the Nd-Fe-B-based thin film because a small amount of impurities are mixed and a high quality crystalline film can be obtained.

As a base material for forming a thin film, various metals, alloys, glass, silicon, ceramics, etc. can be selected and used. However, in order to obtain a desired crystal structure, it is necessary to perform the treatment at a high temperature, and of course, it is most preferable to select a high melting point metal such as Fe, Mo, Ti or the like as the ceramics and the metal substrate. In the case where the substrate has soft magnetic properties, metals or alloys such as Fe, magnetic stainless steel, and Ni are preferred because the semi-magnetic field of the thin film magnet is reduced. In addition, when the ceramic substrate is used, the resistance to high temperature treatment is sufficient, but the adhesion with the Nd-Fe-B film may be insufficient. As a countermeasure, usually, a base film such as Ti or Cr is provided for adhesion. Is usually performed, and even if the base film is a metal or an alloy, it may be effective.

(Heat treatment)

In the state formed by sputtering or the like, the Nd-Fe-B-based film is usually made of amorphous or fine crystals of several tens of nm. Therefore, conventionally, crystallization and crystal growth are promoted by low temperature heat treatment at 400-650 degreeC, and the crystal structure of less than 1 micrometer is obtained. In the present invention, firstly, it is necessary to produce larger crystal grains than before, and secondly, to carry out high temperature heat treatment at 700 to 1200 ° C in order to coexist Nd enriched grain boundary phase.

The role of this high temperature heat treatment is to promote grain growth of Nd ₂ Fe ₁₄ B crystals in the film and to produce Nd rich grain boundary phases around the crystals. This makes it possible to have a nucleus-type coercive mechanism of the present invention. Preferably, the high temperature heat treatment is followed by low temperature heat treatment at 500 to 600 ° C., whereby the Nd-rich grain boundary phase forms a structure that thinly and uniformly surrounds the crystal, resulting in an improvement in coercivity. There is.

Preferably, the substrate temperature in film-forming is 300-400 degreeC, for example, and it heats to 700-1200 degreeC after film-forming. Below 700 DEG C, it takes tens of hours to grow the desired grains, which is not appropriate, and it is very difficult to produce Nd enrichment grains. When the temperature is 700 ° C or higher, crystal growth progresses and Nd enrichment grains are formed through various reactions of Nd, Fe, and B. However, if it exceeds 1200 DEG C, a portion of the alloy is melted, which is inappropriate because the shape of the thin film collapses and oxidation proceeds remarkably.

Regarding the heat treatment time, in order to obtain a homogeneous crystal structure, unevenness of grain size and irregular grain boundary thickness of Nd-rich grains tends to occur in 10 minutes or less in any one of high temperature and low temperature heat treatment. On the other hand, since the volume of the thin film magnet is smaller than that of the sintered magnet, it is easy to obtain a desired crystal structure or grain boundary phase from tens of minutes to several tens of minutes, and the treatment for 1 hour or more leads to the progress of oxidation or increases the time beyond this. Even if it is used, since the influence on crystal structure is comparatively small, the treatment time of more than 10 minutes and less than 1 hour is preferable.

The heat treatment is preferably carried out in a vacuum or non-oxidizing atmosphere after film formation, and the heating method is a method of mounting a thin film sample in an electric furnace, a method of rapidly heating and cooling by infrared heating or laser irradiation, and a thin film. The joule heating method etc. which directly energize can be employ | adopted.

It is preferable to separate the film and heat treatment because it is easy to control the crystallinity and magnetic properties of the film.However, the substrate is heated to a high temperature during the sputtering process or the temperature during the film formation is increased by increasing the output during film formation. It is also possible to create the desired crystal structure by keeping it. In addition, since Nd-Fe-B-based films are easily rusted, it is common to form and use a corrosion-resistant protective film such as Ni or Ti after film formation or after heat treatment.

1 is a supermagnetization curve and a potato curve of a sintered magnet (a) and a thin film magnet (b) of a conventional example.

2 is a relationship diagram between the amount of Nd and (BH) max of the sample of the present invention and the comparative example sample.

3 is a magnetization curve and a potato curve of the sample (2) of the present invention and the comparative sample (4).

4 is a relationship diagram between the crystal grain size and (BH) max of the sample of the present invention and the comparative example sample.

5 is a relationship diagram between the film thickness of the sample of the present invention and the comparative example sample and (BH) max.

6 is a relationship diagram between the magnetic field and (BH) max of the sample 17 of the present invention and the sample 13 of the comparative example.

(Example 1)

Hereinafter, the present invention will be described in detail with reference to the following examples.

Nd-Fe-B alloy having a composition smaller than the Nd content of the target Nd-Fe-B alloy is melted and cast, and the inner and outer circumferences and the plane grinding are performed, and the outer diameter is 60 mm and the inner diameter 30 mm. And two annular alloys having a thickness of 20 mm were produced. In addition, eight through holes having a diameter of 6 mm were provided in the annular portion by electric discharge machining to prepare a target, and Nd rods having a purity of 99.5% with a diameter of 5.8 mm and a length of 20 mm were prepared for adjustment of alloy composition. In addition, a large number of steel plates having a purity of 99.9% having a length of 12 mm, a width of 5 mm, and a thickness of 0.3 mm were produced, and solvent degreasing and pickling were used as substrates. An Nd-Fe-B alloy was formed on the surface of this steel substrate by using a three-dimensional sputtering device in which the pair of targets were opposed to each other and a high frequency coil was disposed therebetween.

The actual film forming work was performed in the following order. A predetermined number of Nd rods are mounted in the through holes of the Nd-Fe-B alloy target provided in the sputtering apparatus, and the substrate is attached to a jig directly connected to the motor shaft in the apparatus, and placed in the middle of the high frequency coil. Set to be placed. After evacuating the inside of a sputter apparatus to 5x10 <^-5> Pa, Ar gas was introduce | transduced and the inside of the apparatus was kept at 1 Pa. Next, reverse sputtering was performed for 10 minutes by applying RF output 30W and DC output 3W to remove the oxide film on the surface of the steel substrate. Subsequently, 90 minutes of sputtering was performed while applying 150 W of RF output and 300 W of DC output while rotating the substrate at 6 rpm to form an Nd-Fe-B film having a thickness of 15 µm on both sides of the substrate. Subsequently, the same sputter was repeated by changing the number of Nd rods to produce an Nd-Fe-B film having a total of six alloy compositions.

Next, six film-formed substrates were cut in half in the longitudinal direction, and one of them was mounted in an electric furnace installed in a glove box, and the first of the Ar atmospheres kept at an oxygen concentration of 2 ppm or less at 850 ° C. 20 minutes, the second was heat-treated twice for 30 minutes at 600 ℃. The sample obtained here was made into sample (1)-(4) of this invention and comparative sample (1)-(2) according to Nd composition. The other one was heat-treated only once at 600 ° C for 30 minutes to obtain Comparative Example Samples (3) to (8).

As a representative example, for the sample (2) and the comparative example (4) of the present invention in which the Nd content is the same and the highest (BH) max value is obtained, a scanning electron microscope equipped with an energy dispersive mass spectrometer (EDX) ( SEM) was used to observe the crystal structure. The crystal grain size of the sample (2) of the present invention obtained by measuring the length in the observation image was 3 to 4 µm, and in secondary electron image observation, the thickness in which Nd and O were distributed at high concentrations between the crystal grains was 0.2. A grain boundary image of less than or equal to μm was found. On the other hand, the crystal grain size of the comparative example sample 4 was 0.2 micrometer or less, and the clear grain boundary phase could not be confirmed.

In addition, in order to investigate the C-axis direction, which is an axis of easy magnetization of the Nd-Fe-B crystal, magnetic samples in the two directions, vertical and horizontal, with respect to the film formation surface were subjected to the sample 2 and the comparative example 4 of the present invention. Carried out. As a result, it is assumed that the C-axis is oriented in the vertical direction to the film plane, as is apparent from the fact that the residual magnetization of the former sample is 1.6 times when measured in the vertical direction compared to the horizontal. As a result of measuring the X-ray diffraction pattern of this sample, the above-described C-axis orientation was reconfirmed because the diffraction line intensity of the (006) plane due to the Nd ₂ Fe ₁₄ B crystal was remarkable. On the other hand, there was a difference in the residual magnetization degree direction of the latter sample, which was 1.25 times when measured in the vertical direction compared to the horizontal, but the crystal grains were too small so that the orientation of the C-axis fell slightly compared with the electronic sample.

The magnetic properties of each sample were measured using a vibratory sample magnetometer, and the cases where the magnetic field was applied at 1.2 MA / m and 2.4 MA / m in the direction perpendicular to the membrane surface were measured. Next, the Fe substrate before the film-forming which heat-processed at the said temperature was measured, and the magnetic property of the Nd-Fe-B film was calculated | required after subtracting a measured value. In addition, some samples measured the supermagnetization curve further, and did not consider the correction of the semimagnetic field coefficient in any case.

In the alloy composition analysis of the thin film, in the commonly used ICP analysis method, an error due to elution of the Fe substrate occurs when acid dissolving the film, so the Nd content in the film was calculated by EPMA analysis. As a result, the Nd mass% of the comparative sample (1) was 25.7, the inventive sample (1) was 29.4, the inventive sample (2) was 34.5, the inventive sample (3) was 39.2, and the inventive sample (4) was 44.1 and Comparative Example Sample (2) were 47.8. In Comparative Examples samples (3) to (8), in which the heat treatment conditions were different from those described above, a value corresponding to the mass% result was used because there was no change in the Nd mass% due to the difference in heat treatment. Table 1 summarizes the Nd mass and heat treatment conditions.

Nd composition (mass%) Heat treatment temperature (℃) Comparative Example Sample (1) 25.7 850 Invention Sample (1) 29.4 850 Invention Sample (2) 34.5 850 Sample of Invention (3) 39.2 850 Sample of Invention (4) 44.1 850 Comparative Example Sample (2) 47.8 850 Comparative Example Sample (3) 25.7 600 Comparative Example Sample (4) 29.4 600 Comparative Sample (5) 34.5 600 Comparative Example Sample (6) 39.2 600 Comparative Example Sample (7) 44.1 600 Comparative Example Sample (8) 47.8 600

2, the maximum energy product (BH) max of the sample (1)-(4) of this invention and the sample (1)-(8) of a comparative example is shown. Here, the thing measured by adding the low magnetic field of 1.2MA / m was set to (BH) max / 1.2, and the thing which added the high magnetic field of 2.4MA / m was described as (BH) max / 2.4.

As is apparent from Fig. 2, (BH) max depends on the amount of Nd in all the samples, and the maximum energy product (BH) in the samples (1) to (4) of the present invention in which the Nd mass is 28% or more and 45% or less. A high value of at least about 150 kJ / m 3 was obtained with) max / 1.2 and (BH) max / 2.4. In addition, it has been found that the difference between the (BH) max quantum is small and relatively high characteristics can be obtained by a low magnetization magnetic field. Comparative Example Sample (1) having too low Nd mass% had a low coercive force because a precipitate of αFe was confirmed in the crystal structure, so that a high (BH) max was not obtained, and Comparative Example Sample (2) having too much Nd mass%. The residual magnetization was remarkably lowered and a high (BH) max could not be obtained.

On the other hand, in Comparative Samples (3) to (8), the difference between (BH) max / 1.2 and (BH) max / 2.4 is large so that a high value cannot be obtained unless the magnetization magnetic field is enlarged. In this case, a value of 150 kJ / m 3 could be obtained only when a high magnetic field was applied. This is because, as shown in the supermagnetization curve and the potato curve of the sample (2) and the comparative sample (4) of the present invention of FIG. 3, the former has a rapid increase in magnetization, whereas the latter is gentle. Organizational differences are presumed to be the cause.

(Example 2)

In the front chamber of the three-dimensional sputtering apparatus, three Nd rods were attached to the pair of Nd-Fe-B alloy targets produced in Example 1, and Ti targets having the same dimensions were mounted in the rear chamber. did. As the substrate, alumina having a surface polish of an outer diameter of 10 mm, an inner diameter of 0.8 mm, and a thickness of 0.2 mm was used. The alumina substrate was attached to the tungsten wire having a corrugation process having a diameter of 0.5 mm and a length of 60 mm directly attached to the jig directly attached to the motor shaft.

After evacuating the inside of the sputter apparatus, Ar gas was introduced to maintain the inside of the apparatus at 1 Pa, and the substrate was rotated at 6 rpm. Initially, the RF output 100W and the DC output 10W were applied for 10 minutes of reverse sputtering, followed by the RF 100W and DC 150W for 10 minutes of sputtering to form a base film of Ti on both sides of the substrate. . Subsequently, the Ti film-forming substrate was transferred to the entire chamber of the apparatus, RF 200W and DC 400W were applied to sputter for 80 minutes, and Nd-Fe-B films were formed on both surfaces of the substrate. Furthermore, these substrates were mounted in an electric furnace placed in an Ar gas atmosphere, heated at 600 to 1250 ° C. for 30 minutes, cooled, and various samples having a difference in crystal grain size due to a difference in heat treatment temperature, that is, a sample of the present invention. (5)-(9) and Comparative Example Samples (9)-(10) were used.

The thickness of each film formed into a film was masked on a part of the substrate in advance to form a film under the same sputtering conditions, and measured by surface roughness measurement. As a result, the Ti film was 0.15 µm and the Nd-Fe-B film was 20 µm. In addition, the amount of Nd in the Nd-Fe-B film was 33.2 mass%. The samples after heat treatment were all observed using an SEM apparatus equipped with an EDX analysis function, and the Nd ₂ Fe ₁₄ B crystal grain size was obtained from the image. According to the secondary electron image observation, in the samples (5) to (9) of the present invention, grain boundaries having a thickness of approximately 0.1 µm in which Nd and O were distributed at high concentrations between the crystal grains were confirmed. On the other hand, in the comparative samples (9) to (10), no clear grain boundary phase was found.

Table 2 shows the values of residual magnetization Br / 1.2 and coercive force Hcj / 1.2 when 1.2 MA / m of low magnetic field is applied to the heat treatment temperature, crystal grain size, and film surface of each sample.

Sample Name Heat treatment temperature (℃) Grain size (㎛) Br / 1.2 (T) Hcj / 1.2 (MA / m) Comparative Example Sample (9) 600 0.2 0.58 1.18 Sample of the Invention (5) 700 0.7 0.83 1.22 Invention Sample (6) 800 3.1 1.03 1.15 Invention Sample (7) 900 9.2 1.18 1.12 Sample of Invention (8) 1000 18 1.19 0.93 Invention Sample (9) 1200 28 1.16 0.74 Comparative Example Sample (10) 1250 35 0.87 0.38

As clearly shown in Table 2, when the heat treatment temperature is 700 ° C or higher, a grain size exceeding 0.3 µm of the terminal sphere particle diameter is obtained, and as the temperature becomes high, the crystal grows and the grain size increases. Comparative Example Sample 9 had a small grain size and a large coercive force, but had a low magnetization, resulting in low residual magnetization. Comparative Example Sample 10 had an excessively grain size, so the coercive force was remarkably lowered, resulting in a decrease in residual magnetization. Furthermore, the alloy component was partially melted and the surface of the film was uneven.

4 shows the relationship between the crystal grain size of each sample and (BH) max / 1.2 and (BH) max / 2.4. As shown in Fig. 4, as the grain size increases, the value of (BH) max / 1.2 becomes closer to the value of (BH) max / 2.4, that is, the magnetism is improved. Moreover, (BH) max / 2.4 is 150 kJ / m <3> or more in the sample (5)-(9) of this invention which has a grain size of 0.7-27 micrometers, 200 kJ / m <3> or more in (6)-(8), and a maximum of 245 kJ / m <3>. As a result, high maximum energy gain was obtained.

(Example 3)

Two Nd rods and one Dy rod were attached to a pair of Nd-Fe-B alloy targets, and two Fe substrates used in Example 1 were fixed to the jig and adhered to the sputtering apparatus. The inside of the device is kept at 0.5 Pa, the substrate is rotated at 6 rpm, and the RF output 30W and the DC output 4W are first applied for 10 minutes reverse sputtering, and the RF 200W and DC 500W are applied to the sputter for 0.5 minutes to 24 hours. The Nd-Dy-Fe-B film was formed on one surface of the two substrates. One substrate was used for film thickness measurement and the other substrate was used for heat treatment. The heat treatment rapidly heated these substrates to 820 degreeC by infrared-heating in vacuum, hold | maintained for 10 minutes, and cooled. The obtained sample was made into the comparative example sample 11 of 0.15 micrometer, the sample 10 of this invention (10)-374 micrometers of this invention sample, and the comparative example sample 12 of 455 micrometers, respectively, according to the film thickness.

The composition analysis of each sample showed that the Nd content in the Nd-Dy-Fe-B film was 29.8 mass%, the Dy was 4.3 mass%, and the total rare earth amount was 34.1 mass%. In addition, all the crystal grain diameters were the range of 5-8 micrometers. From the secondary electron image observation, the grain boundary phase whose thickness in which Nd and O were distributed in high concentration between each crystal grain in all samples was 0.2 micrometer or less was confirmed.

5 shows the relationship between the film thickness of each sample and (BH) max / 1.2 and (BH) max / 2.4. As can be clearly seen from Fig. 5, the comparative example sample 11 having a film thickness of 0.15 占 퐉 is so thin that the crystal volume is so small that the behavior of the terminal sphere coercive force mechanism becomes dominant, resulting in poor magnetization. The difference between (BH) max / 1.2 and (BH) max / 2.4 is large. Moreover, the sample 12 of the comparative example showed the tendency for (BH) max to fall because the film | membrane was too thick, and the disorder of the vertical orientation of a crystal | crystallization became large. Therefore, it was evident that it was appropriate to set the film thickness to 0.2 to 400 mu m to obtain high energy.

(Example 4)

The target was the same as Example 3, and the base material used the axis | shaft of the SUS420 type stainless steel product of diameter 0.3mm and length 12mm. While maintaining the inside of the apparatus at 1 Pa, while rotating the substrate at 10 rpm, the RF output 20 W and the DC output 2 W were applied for 10 minutes of reverse sputtering, and the RF 200 W and DC 500 W were applied for 4 hours to sputter the surface of the substrate shaft. Two 46-micrometer Nd-Dy-Fe-B films were formed. Subsequently, the shaft formed into a film was mounted in the electric furnace, one side was hold | maintained at 800 degreeC, and the other was hold | maintained for 30 minutes at 550 degreeC, and the former was made into the sample 17 of this invention, and the latter was made into the comparative sample 13.

As a result of composition analysis of each sample, the amount of Nd in the Nd-Dy-Fe-B film was 30.6 mass%, the Dy was 4.4 mass%, and the total rare earth amount was 35.0 mass%. Moreover, the grain size of the sample 17 of this invention was 3-7 micrometers, The grain boundary phase whose thickness which distributed Nd and O in high concentration between each crystal grain was 0.2 micrometer or less was confirmed from secondary electron image observation. On the other hand, in the sample 13 of Comparative Example, the crystal grain size was about 0.2 µm, and no clear grain boundary phase was found.

The magnetic properties were measured by adding a magnetic field of 0.8 to 2.4 MA / m in the direction perpendicular to the film-forming axis, and excluding Nd-Dy-Fe after removing the properties of the sample obtained by heat-treating the axis before film formation at the same temperature as in Example 1. The magnetic properties of the -B film were obtained. In addition, since the value of residual magnetization was the same level when the result measured by applying a magnetic field in the direction parallel to an axis was compared with the said result, it is guessed that the film | membrane of the equilateral direction was obtained magnetically in this example sample.

6, the relationship of the maximum energy product with respect to a magnetic field is shown with respect to the sample 17 of this invention, and the comparative example sample 13. In FIG. As apparent from FIG. 6, the sample 17 of the present invention had a small maximum difference in energy with respect to the magnitude of the magnetic field compared to the sample 13 of the comparative example, indicating that a high value was obtained at a low magnetic field.

In R-Fe-B thin film magnets having controlled R content and grain size, a complex structure of R ₂ Fe ₁₄ B crystals and grain boundaries of R elements is formed to form a conventional structure. Compared with thin film magnets, thin film magnets with superior magnetism could be manufactured. As a result, it is possible to sufficiently magnetize micromachines, sensors, and small sized thin-film magnets for medical and information equipment, which are difficult to generate a strong magnetic field in a narrow space, thereby contributing to the improvement of high performance of various devices.

Claims (4)

In the R-Fe-B type alloy containing 28-45 mass% of R elements (wherein R is one kind or two or more kinds of rare earth lanthanide elements), the grain size is 0.5 to 30 µm. An R-Fe-B thin film magnet having a complex structure with an R ₂ Fe ₁₄ B crystal and a grain boundary phase in which R elements are enriched at the boundary of the crystal. The R-Fe-B-based thin film magnet according to claim 1, wherein the C axis, which is an axis of easy magnetization of the R ₂ Fe ₁₄ B crystal, is non-oriented or oriented almost perpendicular to the film plane. The R-Fe-B-based thin film magnet according to claim 1 or 2, wherein the film thickness is 0.2 to 400 µm. It is characterized by grain growth and the formation of grain boundary phases in which R elements are enriched by heating to 700 to 1200 ° C. during the physical deposition and / or subsequent heat treatment of the R-Fe-B alloy. The manufacturing method of the R-Fe-B type thin film magnet in any one of Claims 1-3.

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