Nano-granular bulk member and method for manufacturing the same

Abstract

To provide a bulk member having the same magnetic property as that of a thin film having a nano-granular structure, and a method for manufacturing the bulk member.SOLUTION: A nano-granular bulk member 1 has a nano-granular structure in which nano magnetic particles 11 made of at least one type of element selected from Fe, Co, and Ni are dispersed in a matrix 10 including a fluorine compound, an oxygen compound, or a nitrogen compound of at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi, and a rare-earth element. The volume occupation rate of the nano-magnetic particles 11 is in the range of 10-70%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bulk member having a nanogranular structure and a method for producing the same. [Background technology]

[0002] The present applicant has proposed a magnetic thin film having a nanogranular structure in which nanometer-sized metal particles are dispersed in an insulating matrix (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6619216 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the reality is that the range of applications for thin films is limited.

[0005] An object of the present invention is to provide a bulk member having magnetic properties similar to those of a thin film having a nanogranular structure, and a method for producing the same. [Means for solving the problem]

[0006] The nanogranular bulk member of the present invention comprises: It has a nanogranular structure in which nanomagnetic particles made of one or more elements selected from Fe, Co, and Ni are dispersed in a matrix containing a fluorine compound, oxygen compound, or nitrogen compound of at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi, and rare earth elements, The volume occupancy rate of the nanomagnetic particles is in the range of 10 to 70%.

[0007] The method for producing a nanogranular bulk member of the present invention includes the steps of: a step of preparing a thin film having a nanogranular structure in which nanomagnetic particles made of one or more elements selected from the group consisting of Fe, Co, and Ni are dispersed in a matrix made of a fluorine compound, oxygen compound, or nitrogen compound of at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi, and rare earth elements; At least one of the steps of: preparing first magnetic particles having the nanogranular structure by pulverizing the thin film; and extracting second magnetic particles composed of the nanomagnetic particles and a protective film derived from the matrix by dissolving the thin film in water. and pressing at least one of the first magnetic particles and the second magnetic particles into a molded shape. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a nanogranular bulk member according to one embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating the configuration of a first magnetic particle. [Figure 3] FIG. 3 is a diagram illustrating the configuration of a second magnetic particle. [Figure 4] FIG. 2 is an explanatory diagram of the structure of a mixed particle of first magnetic particles and second magnetic particles. [Figure 5] FIG. 1 is an explanatory diagram of the relationship between the magnetic metal content and the average particle size of nanomagnetic particles. [Figure 6A] FIG. 1 is an explanatory diagram of the relationship between the magnetic metal content and the particle size distribution of nanomagnetic particles. [Figure 6B] FIG. 1 is an explanatory diagram of the relationship between the magnetic metal content and the particle size distribution of nanomagnetic particles. [Figure 7] FIG. 10 is an explanatory diagram of the relationship between the temperature of the substrate and the particle size distribution of the nanomagnetic particles. [Figure 8] FIG. 3 is an explanatory diagram showing the magnetization curves of the nanogranular thin film and the second magnetic particles. [Figure 9] FIG. 1 is an explanatory diagram of frequency characteristics of complex permeability of a bulk member (sample 1). [Figure 10]FIG. 10 is an explanatory diagram of the frequency characteristics of the complex permeability of a bulk member (sample 2). DETAILED DESCRIPTION OF THE INVENTION

[0009] (Structure of nanogranular bulk material) A nanogranular bulk member 1 according to one embodiment of the present invention, shown schematically in Figure 1, has a nanogranular structure in which nanomagnetic particles 11 are dispersed in a matrix 10. The term "bulk member" refers to a member whose width and height (thickness) each exceed the standard thickness range of a nanogranular thin film, for example, approximately 0.3 to 5 µm.

[0010] The matrix 10 is made of a fluorine compound, an oxygen compound or a nitrogen compound of at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi and rare earth elements.

[0011] The nanomagnetic particles 11 are made of a magnetic metal or its alloy. At least one ferromagnetic metal selected from Fe, Co, Ni, and Gd is used as the magnetic metal. Additionally or alternatively, at least one diamagnetic metal selected from Au, Ag, Cu, and Zn may be used as the magnetic metal. Examples of magnetic metal alloys include Fe-Pt alloys, Fe-Pd alloys, Co-Pt alloys, Co-Pd alloys, silicon steel (Fe-Sn alloys), permalloy (Ni-Fe alloys), sendust (Fe-Si-Al alloys), permendur (Fe-Co alloys), and soft ferrites, as well as alnico (Al-Ni-Co alloys), ferrite, samarium cobalt (Sm-Co alloys), neodymium iron boron (Nd-Fe-B alloys), and samarium iron nitrogen (Sm-Fe-N alloys), which are used to make magnets. The particle size of the nanomagnetic particles 11 is, for example, in the range of 1 to 50 nm or 1 to 20 nm. The volume occupancy rate of the nanomagnetic particles 11 is in the range of 10 to 70%.

[0012] (Method for producing nanogranular bulk materials) To fabricate the nanogranular bulk component shown in FIG. 1, a nanogranular thin film is first fabricated (STEP 1). The nanogranular thin film is fabricated, for example, by sputtering or RF sputtering (see, for example, Patent Document 1). Sputtering is performed using a composite target in which chips of a water-soluble (deliquescent) fluorine compound, or an oxygen compound or a nitrogen compound are evenly arranged on a disk of a magnetic metal or its alloy, or a target consisting of a magnetic metal or its alloy and a water-soluble (deliquescent) fluorine compound, or an oxygen compound or a nitrogen compound. Ar gas is used for sputtering. The film thickness of the nanogranular thin film is adjusted by adjusting the film formation time, and is typically approximately 0.3 to 5 μm thick. The substrate is indirectly water-cooled or maintained at a temperature ranging from 100 to 800°C. The sputtering pressure during film formation is controlled to fall within the range of 1 to 60 mTorr. The sputtering power is controlled to fall within the range of 50 to 350 W.

[0013] This results in the production of a nanogranular thin film having a nanogranular structure in which nanomagnetic particles 11 primarily composed of L are uniformly dispersed in a matrix 10 primarily composed of a fluoride of M (see Figure 1). The nanogranular thin film has a composition expressed as LMF, LMO, or LMN, where L is one or more elements selected from Fe, Co, and Ni; M is at least one element selected from Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi, and rare earth elements; F is fluorine; O is oxygen; and N is nitrogen. The atomic ratio of M is in the range of 0.10 to 0.40, the atomic ratio of F, O, or N is in the range of 0.20 to 0.70, and the total atomic ratio of M and F, O, or N is in the range of 0.30 to 0.60.

[0014] The particle size of the nanomagnetic particles 11 is, for example, in the range of 1 to 50 nm or 1 to 20 nm. The particle size distribution of the nanomagnetic particles 11 can be adjusted by changing the film formation conditions and / or the film formation composition.

[0015] Figure 5 shows the relationship between the content of the magnetic metals Fe and Co in an Fe-Co-Mg-F nanogranular structure material and the average particle size of the nanomagnetic particles 11. As can be seen from Figure 5, as the content of Fe and Co changes from approximately 10 at% to approximately 70 at%, the average particle size of the nanomagnetic particles 11 changes linearly from approximately 2 nm to approximately 8 nm. In this way, the average particle size of the nanomagnetic particles 11 can be adjusted by adjusting the content of the magnetic metal or alloy in the nanogranular thin film.

[0016] FIG. 6A shows the particle size distribution of nanomagnetic particles 11 when the content of magnetic metals Fe and Co in an Fe-Co-Mg-F nanogranular thin film is 24 at %. FIG. 6B shows the particle size distribution of nanomagnetic particles 11 when the content of magnetic metals Fe and Co in an Fe-Co-Mg-F nanogranular thin film is 30 at %. Comparing FIGS. 6A and 6B reveals that the particle size distribution of nanomagnetic particles 11 (such as the maximum particle size frequency and variance) changes as the content of Fe and Co changes. Thus, the particle size distribution of nanomagnetic particles 11 can be adjusted by adjusting the content of the magnetic metal or alloy in the nanogranular thin film.

[0017] Figure 7 shows the relationship between the substrate temperature and the average particle size of the nanomagnetic particles 11 when an Fe-Co-Al-F nanogranular thin film is fabricated by sputtering. As can be seen from Figure 7, as the substrate temperature changes from approximately 20°C to approximately 610°C, the average particle size of the nanomagnetic particles 11 changes exponentially from approximately 3 nm to approximately 20 nm. In this way, the average particle size of the nanomagnetic particles 11 in the nanogranular structure material can be adjusted by adjusting the film formation conditions, such as the substrate temperature.

[0018] (Preparation of first magnetic particles) A nanogranular thin film is formed on a substrate coated with resist as described above, and the nanogranular thin film is then immersed in an organic solvent together with the substrate, and the nanogranular thin film is separated from the substrate. The nanogranular thin film is then appropriately dried and pulverized to produce first magnetic particles PM1 with a particle size of 0.1 to 5 μm (STEP 2-1). The pulverization process produces first magnetic particles PM1 of a nanogranular thin film containing a matrix of oxygen and nitrogen compounds that do not exhibit deliquescent properties. As shown in FIG. 2, the first magnetic particles PM1 have a nanogranular structure in which nanomagnetic particles 11 are dispersed in a matrix 10.

[0019] (Preparation of second magnetic particles) The nanogranular thin film is dissolved in water, thereby extracting or producing second magnetic particles PM2 (STEP 2-2). The matrix 10 constituting the nanogranular thin film is made of a fluorine compound and is therefore soluble in water. Meanwhile, the fluorine compounds present around the nanomagnetic particles 11 constituting the nanogranular thin film are bound to the magnetic metal or alloy constituting the nanomagnetic particles 11 by electromagnetic force or intermolecular force. Therefore, as shown schematically in Figure 3, second magnetic particles PM2 are extracted, each composed of the nanomagnetic particles 11 and a protective film 12 derived from the matrix 10. The protective film 12 is made of a fluorine compound of at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, and Ba. The thickness of the protective film 12 is presumed to be at the molecular level.

[0020] For example, the second magnetic particles PM2 are extracted by filtering an aqueous solution of the nanogranular thin film, and the filtrate is dried to obtain the second magnetic particles PM2. The aqueous solution of the Fe-Co-Ba-F nanogranular thin film is initially colorless and transparent, but gradually takes on a yellowish tint, and finally, the second magnetic particles PM2 aggregate, turning the aggregates brown.

[0021] In Figure 8, the magnetization curve of the Fe-Co-Ba-F nanogranular thin film is shown by the dashed line, and the magnetization curve of the second magnetic particle PM2 extracted by dissolving the nanogranular thin film in water is shown by the solid line. Figure 8 shows that the second magnetic particle PM2 exhibits magnetic properties similar to those of the nanogranular thin film. This confirms that the nanomagnetic particle 11 is not oxidized and is entirely covered with a protective film 12 made of a fluorine compound to prevent contact with water.

[0022] (Press molding) The first magnetic particles PM1 and / or the second magnetic particles PM2 are pressed into a mold device to produce a nanogranular bulk member 1 of a specified shape (STEP 3). Depending on the application, the nanogranular bulk member 1 may be molded into various plate shapes such as annular plates, triangular plates, rectangular plates, regular polygonal plates, and trapezoidal plates, or may be molded into various three-dimensional shapes such as cones, truncated cones, rectangular parallelepipeds, and regular polyhedra.

[0023] In the nanogranular bulk member 1 shown in FIG. 2, which is produced using only the first magnetic particles PM1, the volume occupancy of the nanomagnetic particles 11 is in the range of 10 to 60%. In this case, the average spacing between the nanomagnetic particles 11 is in the range of 0.2 to 10 nm. In this case, the step of producing the second magnetic particles PM2 (STEP 2-2) may be omitted. When PM1 is produced using an oxygen compound and a nitrogen compound that are not deliquescent, the step of producing the second magnetic particles PM2 (STEP 2-2) may be omitted as long as the nanomagnetic particles 11 are in the above range.

[0024] 3, the nanogranular bulk member 1 produced using only the second magnetic particles PM2 has a volume occupancy rate of the nanomagnetic particles 11 in the range of 30 to 70%. In this case, the average spacing between the nanomagnetic particles 11 is in the range of 0.2 to 10 nm. In this case, the step of producing the first magnetic particles PM1 (STEP 2-1) may be omitted.

[0025] In the nanogranular bulk member 1 produced using mixed particles of first magnetic particles PM1 and second magnetic particles PM2 shown in Figure 4, the volume occupancy of the nanomagnetic particles 11 is in the range of 10 to 60%. In this case, the average spacing between the nanomagnetic particles 11 is in the range of 0.2 to 10 nm. By preparing multiple mixed particles with different mixing ratios of the first magnetic particles PM1 and the second magnetic particles PM2 and sequentially stacking and press-molding them in an order appropriate for the application, a nanogranular bulk member 1 is produced having a layered structure in which the volume occupancy of the nanomagnetic particles 11 in each layer, and therefore the magnetic properties, change regularly in the stacking direction (specified direction).

[0026] (Performance evaluation) The nanogranular bulk member 1 was formed in the shape of a roughly circular ring plate with an outer diameter of 20 mm, an inner diameter of 14 mm, and a thickness of 1 mm. Figure 9 shows the measurement results of the frequency dependence of the complex permeability of the nanogranular bulk member 1 (Sample 1), in which the magnetic metals Fe and Co in the Fe-Co-Mg-F nanogranular thin film are contained in an amount of 14 to 20 at%. Figure 10 shows the measurement results of the frequency dependence of the complex permeability of the nanogranular bulk member 1 (Sample 2), in which the magnetic metals Fe and Co in the Fe-Co-Mg-F nanogranular thin film are contained in an amount of 24 to 31 at%. Figures 9 and 10 show that the complex permeability μ' of Sample 1 and Sample 2 is maintained high from the MHz to GHz bands, and that the magnetic loss μ" is small, at 1 or less, and that the ferromagnetic resonance frequency exceeds 1 GHz of the measured magnetic field.

[0027] (Application) The nanogranular bulk material 1 of the present invention is a highly useful material that can be applied to electromagnetic wave shielding materials, medical magnetic beads, electromagnetic noise absorbers, high-frequency magnetic materials, magnetic yokes, magnetic cores, high-density recording magnetic media, biomolecule labeling materials, drug carriers, nanoscale electronics, permanent magnet materials, electromagnetic shielding materials, and superparamagnetic materials, etc. [Explanation of symbols]

[0028] 1. Nanogranular bulk materials 10. The Matrix 11. Nanomagnetic particles 12‥Protective film PM1‥1st magnetic particle PM2‥Second magnetic particle.

Claims

1. A nanogranular structure in which nanomagnetic particles composed of one or more elements selected from Fe, Co, and Ni are dispersed in a matrix containing a fluorine compound, an oxygen compound, or a nitrogen compound of at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi, and rare earth elements, wherein the volume occupancy of the nanomagnetic particles is in the range of 10 to 70%, a nanogranular bulk member.

2. In the nanogranular bulk member according to Claim 1, there exists a region where the volume occupancy of the nanomagnetic particles is in the range of 10 to 60%, a nanogranular bulk member.

3. In the nanogranular bulk member according to Claim 1, there exists a region where the volume occupancy of the nanomagnetic particles is in the range of 30 to 70%, a nanogranular bulk member.

4. In the nanogranular bulk member according to Claim 2 or 3, the nanogranular bulk member is configured such that the volume occupancy of the nanomagnetic particles changes regularly with respect to the specified direction. a nanogranular bulk member.

5. A step of producing a thin film having a nanogranular structure in which nanomagnetic particles composed of one or more elements selected from Fe, Co, and Ni are dispersed in a matrix composed of a fluorine compound, an oxygen compound, or a nitrogen compound of at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi, and rare earth elements, a step of producing the first magnetic particles having the nanogranular structure by pulverizing the thin film, and a step of extracting the second magnetic particles composed of the nanomagnetic particles and a protective film derived from the matrix by dissolving the thin film in water, at least one of the steps, including a step of press-molding at least one of the first magnetic particles and the second magnetic particles. A method for producing a nanogranular bulk member.

6. In the method for producing a nanogranular bulk member according to Claim 5, a method for producing a nanogranular bulk member including a step of press-molding a mixed particle of the first magnetic particles and the second magnetic particles.

7. In the method for producing a nanogranular bulk member according to Claim 6, including a step of sequentially press-molding each of the mixed particles having different mixing ratios of the first magnetic particles and the second magnetic particles in the specified direction. Method for producing a nanogranular bulk member.

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