MATERIAL WITH NANOGRANULAR STRUCTURE AND METHOD FOR PRODUCING IT

Abstract

Material with nanogranular structure, comprising: a matrix formed from a fluorine compound with a composition represented by MF, and Metal oxide nanoparticles dispersed in the matrix and having a composition represented by LO, wherein the material with nanogranular structure has a composition represented by LMFO, wherein L is at least one element selected from the group consisting of Fe, Co and Ni, M is at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi and rare earth elements, F is fluorine, O is oxygen and an atomic fraction of L is within a range of 0.03 to 0.50, an atomic fraction of M is within a range of 0.03 to 0.30, an atomic fraction of F is within a range of 0.06 to 0.65 and an atomic fraction of O is within a range of 0.04 to 0.50, and where an absolute value of a Faraday rotation angle for light in a wavelength range of 1350 to 1650 [nm] lies within a range of 0.1 [degrees / µm] or more and where the light transmittance for light in a wavelength range of 1000 to 1675 [nm] is in the range of 40 [% / µm] or more.

Description

Technical area

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

[0002] The applicant of the present application has proposed a magnetic thin film having a nanogranular structure in which nanometer-sized metal particles are dispersed in an insulator matrix (see Patent Literature 1).

[0003] The document JP 2021 - 27 222 A further discloses a magneto-optical thin film comprising an insulating matrix and metal particles dispersed therein, which contain at least one of the elements Fe, Co and Ni and which are represented by the composition formula Fe a Co b Ni c M w N x O y F zwherein M is at least one element selected from a group consisting of B, Mg, Al, Si, Ti, Y, Zr, Nb, Hf, In, Sn, Zn and Ta, wherein the metal particles have an average particle diameter in a range of 3.0-20.0 [nm], wherein the average particle spacing is in a range of 0.5-2.0 [nm], and wherein the aspect ratio is in a range of 1.0-1.2. List of cited literaturePatent literature

[0004] Patent Literature 1: Japanese Patent No. JP 6 619 216 B2 Summary of the inventionTechnical problem

[0005] The object of the present invention is to provide a novel material with a nanogranular structure having magneto-optical properties different from those of existing materials with a nanogranular structure, and a method for producing the same. Solution to the problem

[0006] The nanogranular structure material of the present invention comprises: a matrix formed from a fluorine compound having a composition represented by MF; and Metal oxide nanoparticles dispersed in the matrix and having a composition represented by LO, wherein the material with nanogranular structure has a composition represented by LMFO, wherein L is at least one element selected from the group consisting of Fe, Co and Ni, M is at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi and rare earth elements, F is fluorine, O is oxygen and the atomic fraction of L is in the range of 0.03 to 0.50, the atomic fraction of M is in the range of 0.03 to 0.30, the atomic fraction of F is in the range of 0.06 to 0.65 and the atomic fraction of O is in the range of 0.04 to 0.50, wherein an absolute value of a Faraday rotation angle for light in a wavelength range of 1350 to 1650 [nm] is within a range of 0.1 [degree / µm] or more, and wherein a light transmittance for light in a wavelength range of 1000 to 1675 [nm] is in a range of 40 [% / µm] or more.

[0007] A method for producing the nanogranular structure material of the present invention comprises a step of preparing a primary nanogranular structure material comprising a matrix having a composition represented by MF and metal nanoparticles having a composition represented by L dispersed in the matrix by a sputtering method, and a step of heat-treating a primary nanogranular structure material formed of a matrix having a composition represented by MF and metal nanoparticles having a composition represented by L dispersed in the matrix in a temperature range of 300 to 800°C in an oxygen-containing atmosphere to produce the nanogranular structure material as a secondary nanogranular structure material. Short description of the drawings Fig.1 shows a schematic representation of a material with a nanogranular structure as an embodiment of the present invention. Fig. Figure 2 shows an illustrative view of the manufacturing conditions for the nanogranular structure material of the example. Fig. Figure 3 shows an illustrative view of the XRD analysis results of each sample of the material with nanogranular structure. Fig. Figure 4 shows an illustrative view of the wavelength dependence of the light transmittance of each sample of the material with nanogranular structure. Fig. Figure 5 shows an illustrative view of the wavelength dependence of the Faraday rotation angle of the nanogranular structure material of the example. Description of the embodiments (configuration of the material with nanogranular structure)

[0008] A material having a nanogranular structure (secondary material having a nanogranular structure) as an embodiment of the present invention, which is described in Fig. 1 is a material with a nanogranular structure in which metal oxide nanoparticles 11 are dispersed in a matrix 12 consisting of a fluorine compound. A material with a nanogranular structure has, for example, a composition represented by LMFO, where L is one or more elements selected from Fe, Co, and Ni, M is at least one or more elements selected from Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi, and rare earth elements, F is fluorine, and O is oxygen.

[0009] The atomic fraction of L ranges from 0.03 to 0.50, the atomic fraction of M ranges from 0.03 to 0.30, the atomic fraction of F ranges from 0.06 to 0.65, and the atomic fraction of O ranges from 0.04 to 0.50. The total atomic fraction of L and O ranges from 0.07 to 0.88. The total atomic fraction of M and F ranges from 0.12 to 0.93. The metal oxide nanoparticles 11 have a composition mainly represented by L O. The matrix 12 is mainly composed of a fluorine compound with a composition represented by M F. The total atomic fraction of L, M, F, and O is one.

[0010] The light transmittance of the material with nanogranular structure for light in the wavelength range of 1000 to 1675 [nm] is in the range of 40% or more at an optical path length of 1 µm.

[0011] The Faraday rotation angle of the material with nanogranular structure for light in the wavelength range of 500 to 680 and 720 to 1000 [nm] in the visible light range is within 0.1 [degree / µm] or more in absolute value.

[0012] The Faraday rotation angle of the nanogranular structure material for light in the wavelength range of 1350 to 1650 [nm], which is the wavelength band for optical communication, is within a range of 0.1 [degree / µm] or more in absolute value. (Process for producing the material with nanogranular structure)

[0013] A process for producing a material with a nanogranular structure with the Fig.1 is described. First, a primary material with a nanogranular structure is prepared (STEP 1). The primary material with a nanogranular structure is prepared, for example, by a sputtering method or an RF sputtering method (see, for example, Patent Literature 1). Sputtering is performed by using a composite target in which chips of a fluorine compound are uniformly arranged on a disk of a magnetic metal or an alloy thereof, or by simultaneously using a target of a magnetic metal or an alloy thereof with a target made of a fluorine compound. Ar gas is used for sputtering deposition. The film thickness of the material with a nanogranular structure is controlled by adjusting the deposition time, and the film is formed to a thickness of, for example, about 0.3 to 5 μm.A substrate is cooled indirectly with water or maintained at any temperature within the temperature range of 100 to 800 °C. The sputtering pressure during deposition is adjusted to be in the range of 0.13 to 8.0 N / m. 2 (1 to 60 mTorr). The sputtering power is adjusted to be in the range of 50 to 350 W.

[0014] In this way, a primary material with a nanogranular structure in which magnetic metal nanoparticles are dispersed in a matrix formed from a fluorine compound is prepared. For example, a primary material with a nanogranular structure has a composition represented by LMF, where L is one or more elements selected from Fe, Co, and Ni, M is at least one or more elements selected from Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi, and rare earth elements, and F is fluorine. The atomic fraction of M is in the range of 0.01 to 0.40, the atomic fraction of F is in the range of 0.02 to 0.70, and the total atomic fraction of M and F is in the range of 0.03 to 0.97.The primary nanogranular structure material has a nanogranular structure in which metal nanoparticles with the composition represented by L are uniformly distributed in a matrix formed from a fluoride with a composition represented by MF.

[0015] The particle size of the metal nanoparticles is, for example, in the range of 1 to 50 nm or in the range of 1 to 20 nm. The particle size distribution of the metal nanoparticles (and thus the particle size distribution of the metal oxide nanoparticles 11 in the secondary material with nanogranular structure) can be adjusted by changing the deposition conditions and / or the deposition composition.

[0016] The primary material with nanogranular structure is heat-treated in an oxygen-containing atmosphere in a temperature range of 300 to 800 [°C] to produce a secondary material with nanogranular structure (STEP 2). (Example and comparative examples)(Sample 1 (Comparative Example 1))

[0017] Fe and Co were selected as L, Ba was selected as M, and a primary material with nanogranular structure represented by Fe 44 Co 32 Ba 13 F 11 , was prepared as Sample 1. (Sample 2 (Comparative Example 2))

[0018] As indicated by the dotted line in Fig. 2, Sample 1 was gradually heated from about 50°C to about 600°C over about 3 hours under vacuum, heat-treated at about 600°C for about 1 hour, and then gradually cooled to about 80°C over about 4 hours to prepare Sample 2. The composition of Sample 2 was determined by Fe 44 Co 32 Ba 13 F 11 shown. (Sample 3 (Example))

[0019] In an atmosphere of a gas mixture of Ar gas and O2 gas (the partial pressure of O2 gas was about 1% of the gas mixture), Sample 1 was placed in a position indicated by the dashed line in Fig. 2 to produce sample 3 as a secondary material with a nanogranular structure, which contains the Fe 23 Co 17 Ba3F6O 46 The pressure of the gas mixture of Ar gas and O2 gas was set to about 8.0 N / m 2 (30 [mTorr]) as shown by the solid line in Fig. 2 is shown.

[0020] The upper part of Fig. 3 shows the result of XRD analysis of sample 1 (primary material with nanogranular structure), and the lower part of Fig. Figure 3 shows the result of the XRD analysis of sample 3 (secondary material with nanogranular structure). Fig.Figure 3 shows that the peak derived from Fe and Co, which represent the metal nanoparticles present in Sample 1, is absent in Sample 3, and instead, a peak derived from CoFe2O4, which represents the metal oxide nanoparticles, is present. This means that the primary material with a nanogranular structure was heat-treated in an oxygen-containing atmosphere, thereby oxidizing the metal nanoparticles contained in the primary material with a nanogranular structure and converting them into metal oxide (composite metal oxide) nanoparticles in the secondary material with a nanogranular structure.

[0021] Out of Fig.3 shows that the height of the peak originating from BaF2, which forms the matrix present in Sample 1, is lower in Sample 3. This means that the primary material with a nanogranular structure was heat-treated in an oxygen-containing atmosphere, which degraded the matrix constituting the primary material with a nanogranular structure and transformed it into the matrix of the secondary material with a nanogranular structure.

[0022] In Fig. 4, the wavelength dependence of the light transmittance (optical path length of 1 µm) of sample 1 is shown by a dashed line and the wavelength dependence of the light transmittance of sample 3 is shown by a solid line. Fig.4, with respect to light in the wavelength range for optical communication of 1000 to 1675 [nm], the light transmittance of Sample 1 is 0.5 to 1.0% (optical path length of 1 µm), while the light transmittance of Sample 3 is 58 to 81% (optical path length of 1 µm), which is significantly higher than that of Sample 1.

[0023] Fig. 5 shows the wavelength dependence of the Faraday rotation angle θ F of sample 3 when the magnetic field applied to sample 3 is 796 kA / m (10 [kOe]). Fig. 5 shows that the Faraday rotation angle θ FSample 3 shows the following: a tendency to gradually increase as the wavelength increases from λ = 400 [nm]; a tendency to gradually decrease after showing a maximum value of about 2.5 [degrees / µm] at λ = about 530 [nm]; a tendency to gradually decrease after changing from a positive value to a negative value at λ = about 700 [nm]; a tendency to gradually increase after showing a minimum value of about -1.5 [degrees / µm] at λ = about 750 to 800 [nm]; a tendency to gradually decrease after showing a maximum value of about 0 [degrees / µm] at λ = about 1300 [nm]; a tendency to gradually increase after showing a minimum value of about -1.0 [degrees / µm] at λ = about 1480 [nm]; and a tendency to gradually increase after changing from a negative value to a positive value at λ = approximately 1650 [nm].

[0024] The absolute value of the Faraday rotation angle of the nanogranular structure material for light in the wavelength range of 500 to 680 and 720 to 1000 [nm] in the visible light range is within 0.1 [degree / µm] or more. Furthermore, the absolute value of the Faraday rotation angle of the nanogranular structure material for light in the wavelength range of 1350 to 1650 [nm], the wavelength band of optical communication, is within 0.1 [degree / µm] or more.

[0025] Table 1 summarizes the heat treatment conditions for each of samples 1 to 3, the Faraday rotation angle, and the light transmittance at a wavelength λ = 1550 [nm] at an optical path length of 1 µm. [Table 1] Treatment after deposition Faraday rotation angle at 1550 nm Light transmittance at 1550 nm Sample 1 No (as secluded) 4 (degrees / µm) 0,9% Sample 2 600°C×1h (under vacuum) 5.1 (degrees / µm) 1% Sample 3 600°C×1h (Ar+1 % O (8,0 N / m 2 [30 mTorr])) -0.9 (degrees / µm) 80% Sample 4 Fe8Co5Ba 13 F 46 O 28 -0.13 (degrees / µm) 80% Sample 5 Fe 17 What 12 Ca 19 Ba4F 13 ABOUT 39 -0.72 (degrees / µm) 74% Sample 6 <h2 style=";text-align:left;direction:ltr">Fe<h2 style=";text-align:left;direction:ltr"> 10 <h2 style=";text-align:left;direction:ltr"> Co7Ba8Ca7Y5F<h2 style=";text-align:left;direction:ltr"> 23 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 40 -0.50 (degrees / µm) 70% Sample 7 Fe9Co8Al 13 Ba5F 38 O 27 -0.40 (degrees / µm) 75% Sample 8 Feb 14 Co 10 Li3Mg 12 F 25 O 36 -0.75 (degrees / µm) 47% Sample 9 Feb 12 Co 10 Ni5BeBa 10 F 22 O 36 -0.67 (degrees / µm) 70% Sample 10 <h2 style=";text-align:left;direction:ltr">Fe<h2 style=";text-align:left;direction:ltr"> 16 <h2 style=";text-align:left;direction:ltr"> Co<h2 style=";text-align:left;direction:ltr"> 11 <h2 style=";text-align:left;direction:ltr"> Ba9Si3F<h2 style=";text-align:left;direction:ltr"> 23 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 39 -0.91 (degrees / µm) 55% Sample 11 Feb 19 Co 15 Ba 10 Sr4Bi4F 38 O 10 -1.0 (degrees / µm) 41% (Application)

[0026] Magneto-optical materials exhibiting the Faraday effect are widely used in optical isolators. The nanogranular structure material according to the present invention is a thin-film material with a thickness on the submicrometer order and exhibits a large Faraday effect at a small size. The use of the present material enables the miniaturization and integration of optical isolators and allows application in optical integrated circuits and the like. List of reference symbols 11 metal oxide nanoparticles, 12 Matrix

Claims

[1] Material with nanogranular structure, comprising: a matrix formed from a fluorine compound having a composition represented by MF, and Metal oxide nanoparticles dispersed in the matrix and having a composition represented by LO, wherein the material with nanogranular structure has a composition represented by LMFO, wherein L is at least one element selected from the group consisting of Fe, Co and Ni, M is at least one element selected from the group consisting of Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi and rare earth elements, F is fluorine, O is oxygen and an atomic fraction of L is within a range of 0.03 to 0.50, an atomic fraction of M is within a range of 0.03 to 0.30, an atomic fraction of F is within a range of 0.06 to 0.65 and an atomic fraction of O is within a range of 0.04 to 0.50, and wherein an absolute value of a Faraday rotation angle for light in a wavelength range of 1350 to 1650 [nm] is within a range of 0.1 [degree / µm] or more, and wherein a light transmittance for light in a wavelength range of 1000 to 1675 [nm] is in a range of 40 [% / µm] or more. [2] The nanogranular structure material according to claim 1, wherein an absolute value of a Faraday rotation angle for light in a wavelength range of 500 to 680 [nm] and 720 to 1000 [nm] is within a range of 0.1 [degree / µm] or more. [3] The nanogranular structure material according to claim 1 or 2, wherein the atomic fraction of L is within a range of 0.13 to 0.40, the atomic fraction of M is within a range of 0.08 to 0.20, the atomic fraction of F is within a range of 0.06 to 0.46, and the atomic fraction of O is within a range of 0.1 to 0.

46. [4] A method for producing a nanogranular structure material, comprising a step of preparing a primary nanogranular structure material comprising a matrix having a composition represented by MF and metal nanoparticles having a composition represented by L dispersed in the matrix by a sputtering method, and a step of heat-treating the primary nanogranular structure material in a temperature range of 300 to 800 [°C] in an oxygen-containing atmosphere to produce the nanogranular structure material according to any one of claims 1 to 3 as a secondary nanogranular structure material. [5] A method for producing a material having a nanogranular structure according to claim 4, the method comprising: a first step in which not only the temperature of a substrate is controlled to a first temperature in a range of 300 to 800 [°C], but also the atmospheric pressure of the substrate is controlled to 1.0 × 10 4 [N / m 2 ] or less controlled; and a second step of applying a composite target or a plurality of individual targets of an insulating material consisting of F and at least one element selected from Li, Be, Mg, Al, Si, Ca, Sr, Ba, Bi and rare earth elements, together with a metal consisting of at least one element of Fe, Co and Ni, while controlling a temperature of a substrate to a second temperature within a range of 300 to 800 [°C], setting an atmosphere of the substrate to a non-oxidizing atmosphere and setting an atmospheric pressure of the substrate to a range of 0.1 to 10 [N / m 2] to deposit the primary material with nanogranular structure on the substrate.

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