研究者詳細 - 竹澤　昌晃

論文 - 竹澤　昌晃

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Magnetic Domain Observation of Milled Nanocrystalline Alloy Powder 査読有り国際誌

Takezawa M., Nagaki T., Motozuka S., Sasaki I., Ando Y., Narahara H., Mori N., Shikayama T., Mukai S., Maeda S., Sakima S., Ishii T.

IEEE Transactions on Magnetics ( IEEE ) 59 ( 11 ) 2023年06月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Fe-based nanocrystalline alloys have high magnetic flux density and low loss. Therefore, in this study, the magnetic domain structure of the ball-milled magnetic powders of these nanocrystalline alloys was observed using a Kerr effect microscope. The effect of strain removal heat treatment on the magnetic properties of the powder was also investigated by observing and comparing the magnetic domain structure of the milled powder before and after heat treatment during the preparation process of the nanocrystalline-milled powder. Our findings showed that the strain removal heat treatment changed the size and shape of the magnetic domains to a simple structure. In addition, the domain wall motion was found to be sensitive to the magnetic field, resulting in soft magnetic properties.

DOI： 10.1109/TMAG.2023.3283211

Scopus

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Observation of Magnetic Domains in Amorphous MagneticWires with a Diameter of 10 μm Used in GSR Sensors 査読有り国際誌

M. Takezawa, Y. Harada, Y. Honkura, and S. Honkura

Sensors 23 ( 7 ) 3506-1 - 3506-9 2023年03月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The core of a Gigahertz Spin Rotation (GSR) sensor, a compact and highly sensitive magnetic sensor, is composed of Co–Fe-based amorphous magnetic wire with a diameter of 10 μm. Observations of the magnetic domain structure showed that this magnetic wire has unusual magnetic noise characteristics. Bamboo-shaped magnetic domains a few hundred micrometers in width were observed to form inside the wire, and smaller domains a few micrometers across were observed to form inside these larger domains. The magnetic domain pattern changed abruptly when an external magnetic field was applied to the wire. Herein is shown how these changes may be a source of magnetic noise in the wire.

DOI： 10.3390/s23073506

Scopus

PubMed

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Magnetic Domain Observation of Milled Nanocrystalline Alloy Powder 査読有り国際誌

Takezawa M., Nagaki T., Motozuka S., Sasaki I., Ando Y., Narahara H., Mori N., Shikayama T., Mukai S., Maeda S., Sakima S., Ishii T.

2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023 - Proceedings 2023年01月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Fe-based nanocrystalline alloys have high magnetic flux density and low loss. So, in this study, the magnetic domain structure of ball-milled magnetic powders of these nanocrystalline alloys was observed using a Kerr effect microscope. The effect of strain removal heat treatment on the magnetic properties of the powder was also investigated by observing and comparing the magnetic domain structure of the milled powder before and after heat treatment during the preparation process of the nanocrystalline milled powder. Our findings showed that the strain removal heat treatment changed the size and shape of the magnetic domains to a simple structure. In addition, the magnetic wall motion was found to occur quickly, resulting in soft magnetic properties.

DOI： 10.1109/INTERMAGShortPapers58606.2023.10228715

Scopus

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Realization of logic operations via spin-orbit torque driven perpendicular magnetization switching in a heavy metal/ferrimagnet bilayer 査読有り

Jacob Mathew A., Gao Y., Wang J., Mohammadi M., Awano H., Takezawa M., Asada H., Fukuma Y.

Journal of Applied Physics 135 ( 21 ) 2024年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

Programmable and non-volatile spin-based logic devices have attracted significant interest for use in logic circuits. Realization of logic operations via spin-orbit torque (SOT) driven magnetization switching could be a crucial step in the direction of building logic-in-memory architectures. In this work, we demonstrate experimentally, the realization of four logic operations in a heavy metal/ferrimagnet bilayer structure via SOT switching. We also propose a general scheme for choosing input parameters to achieve programmable logic operations. The bulk and tunable perpendicular magnetic anisotropy and relatively lower saturation magnetization in ferrimagnets are found to make them more energy efficient in performing logic operations, as compared to conventional ferromagnets. Thus, ferrimagnets are promising candidates for use in logic-in-memory architectures, leading to the realization of user-friendly spin logic devices in the future.

DOI： 10.1063/5.0209089

Scopus

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Effect of Mn doping on magnetic properties, magnetic domain structures and microstructures of 2-17 type Sm-Co magnets 査読有り国際誌

Machida H., Fujiwara T., Fujimoto C., Kanamori Y., Inoue K., Takezawa M.

IEEE Transactions on Magnetics 59 ( 11 ) 2023年06月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

Magnetic properties, magnetic domain structures and microstructures of Sm(Fe0.328Cu0.055Zr0.017MnxCobal)7.65 (x=0.005, 0.010) were investigated. Even with Mn content increased, magnetic properties didn’t deteriorate, remanent magnetic flux density, <italic>B</italic>r, maximum energy product, [<italic>BH</italic>]m and squareness, <italic>H</italic>k/<italic>H</italic>cj (<italic>H</italic>k is a reverse magnetic field value when magnetization becomes 90 % of <italic>B</italic>r), exceeded 12 kG, 33.5 MGOe and 70 %, respectively in both samples. However, a mechanism of magnetic reversal was different, reverse magnetic domains were easy to propagate from grain boundaries in x=0.005, grain interior in x=0.010, respectively. In microstructures, Cu concentration increased in grain boundaries, and cell size enlarged with an increase in Mn content. Because microstructures were formed properly and its size was enlarged, which produce strong pinning force, and negative effects by doping non-ferromagnetic element Mn was compensated.

DOI： 10.1109/TMAG.2023.3282679

Scopus

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Microstructure and Magnetic Characterization on Ball-milled Fe-based Nanocrystalline Alloy Sheet 査読有り国際誌

Nagata S., Horibe Y., Hiramoto S., Narahara H., Mori N., Sasaki I., Takezawa M., Ando Y., Shikayama T., Mukai S., Maeda S., Sakima S., Ishii T., Motozuka S.

2023 IEEE International Magnetic Conference - Short Papers, INTERMAG Short Papers 2023 - Proceedings 2023年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

To realize the effective utilization of the end material and its application to a soft magnetic composite, Fe-based nanocrystalline alloy sheets were ball-milled, and platelet particles were obtained, in this work. Instrumental analyses revealed that although a micro strain was introduced into the nanocrystalline α-Fe grains in the achieved alloy powder, almost no changes were found in the amorphous part filled among the grains. The ball-milling treatment greatly increased the coercive force of the pulverized nanocrystalline sheet. Although the coercive force of the alloy powder decreased after the heat treatment, the coercive force remained to be approximately 10 times higher than that of the heat-treated alloy sheet without the ball-milling treatment, even after the heat treatment. The magnetic process of the ball-milled and heat treated nanocrystalline alloy powder will be discussed in detail in the conference based on the obtained results and Lorentz transmission electron microscopy.

DOI： 10.1109/INTERMAGShortPapers58606.2023.10228768

Scopus

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Microstructure and Magnetic Characterization on Ball-Milled Fe-Based Nanocrystalline Alloy Sheet 査読有り国際誌

Nagata S., Horibe Y., Hiramoto S., Narahara H., Mori N., Sasaki I., Takezawa M., Ando Y., Shikayama T., Mukai S., Maeda S., Sakima S., Ishii T., Motozuka S.

Digests of the Intermag Conference 2023-May 2023年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In this work, ball-milled iron (Fe)-based nanocrystalline alloy sheets and obtaining platelet particles are used to effectively utilize the end material and apply it to a soft magnetic composite. The instrumental analysis results reveal that, although a microstrain is introduced into the nanocrystalline α-Fe grains in the achieved alloy powder, the amorphous part filled among the grains experiences almost no change. The ball-milling treatment greatly increases the coercive force of the pulverized nanocrystalline sheet. Although the coercive force of the alloy powder decreases after the heat treatment, it remained approximately 10 times higher than that of the heat-Treated alloy sheet without the ball-milling treatment, even after the heat treatment. The magnetic process of the ball-milled and post-Annealed nanocrystalline alloy powder is discussed based on the results of the synchrotron radiation X-ray analysis and transmission electron microscopy with the Lorentz technique.

DOI： 10.1109/INTERMAG50591.2023.10265082

Scopus

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Recent topics of magnetic domain observation technique of nano-scaled magnetic materials 査読有り

Takezawa M.

IEEJ Transactions on Fundamentals and Materials ( 一般社団法人電気学会 ) 141 ( 2 ) 112 - 117 2021年02月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Recent topics of magnetic domain observation technique of nano-scaled magnetic materials were summarized and reported. Magnetic properties of nano-scaled magnetic materials are highly dependent on the magnetic domain structure inside their magnetic materials. Therefore, an observation technique of the magnetic domain structure of magnetic materials is an extremely important field of technology to improve the performance of various devices. Spatial resolution of the domain observation and the observation technique in high magnetic fields were described.

DOI： 10.1541/ieejfms.141.112

Scopus

CiNii Article

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Influence of oxygen or carbon impurities on domain structure of Sm-Co magnets 査読有り

Takezawa M., Sakakura K., Tanaka J., Machida H., Fujiwara T.

IEEJ Transactions on Fundamentals and Materials ( 一般社団法人電気学会 ) 141 ( 2 ) 133 - 138 2021年02月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Magnetic domain structure changes during a demagnetization process of 2-17 type Sm-Co magnets with different amounts of carbon and oxygen were observed using a Kerr effect microscope. Moreover, the effects of the excess carbon and excess oxygen compositions on the demagnetization process of the magnets were investigated. As a result, it is found that in the Sm-Co magnets with high carbon and oxygen composition, the nucleation of reversal magnetic domains inside grains during the demagnetization process easily occurs at a lower demagnetization field strength. The nucleation of the reversal magnetic domain in grains causes a decrease in a squareness ratio of a demagnetization curve.

DOI： 10.1541/ieejfms.141.133

Scopus

CiNii Article

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Preface to special issue on “recent topics and future prospect of analysis and creation of structure in nano-scaled magnetic materials”. 査読有り

Takezawa M.

IEEJ Transactions on Fundamentals and Materials 141 ( 2 ) 2021年02月

軟X線ナノビーム走査型XMCDによるNd-Fe-B系焼結磁石の結晶方位と磁区構造の関係解析

槙智仁, 古澤大介, 西内武司, 竹澤昌晃

SPring-8/SACLA利用研究成果集 ( 公益財団法人高輝度光科学研究センター ) 9 ( 1 ) 80 - 82 2021年01月

記述言語：日本語掲載種別：研究論文（大学，研究機関等紀要）

Nd-Fe-B 系焼結磁石において結晶方位と磁区構造の関係を明らかにすることを目的とし、配向方向に平行な面において電子線後方散乱回折（EBSD）と BL25SU の軟X線磁気円二色性（MCD）顕微鏡装置による磁区観察を同位置で行った。熱消磁状態では多くの領域において多磁区粒子となっており、磁区は隣接する粒子をまたがって連続する場合が多いことがわかった。また、観察面に対し平行な磁場中で明瞭な磁区構造変化を得ることに成功した。その結果、粒子の磁化容易方向と印加磁場の角度差が大きい場合には磁壁移動が妨げられる可能性があることを示した。

DOI： 10.18957/rr.9.1.80

CiNii Article

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軟磁性金属粉末における磁区の変化挙動が磁気特性におよぼす影響査読有り

佐藤誉将 , 深瀬美紀子 , 竹澤昌晃

電気製鋼 : 大同特殊鋼技報 ( 大同特殊鋼 ) 91 ( 1 ) 13 - 18 2020年07月

記述言語：日本語掲載種別：研究論文（学術雑誌）

Soft magnetic powder cores are used for choke coils, used in DC-DC converters, noise filters, etc. However, the increase of core loss during high frequency driving needs to be improved. Since core loss is related to magnetic domain motion, it is important to observe magnetic domains clearly to understand how to decrease core loss.In this study, the relation between core loss and the magnetic domain motions in various Fe-Si alloy powders has been investigated by observing magnetic domains with a Kerr effect microscope.We concluded as follows:(1) Grain boundaries, vacancies and precipitates prevent the motion of domain walls as pinning sites.(2) The patterns of magnetic domains vary with internal strain, crystal orientation, or segregation in the powders. Change rate of luminance value decreases in powder with complex magnetic domains.(3) Hysteresis loss decreases with increase of change rate of luminance value which quantifies the ease of domain wall motion. Therefore, it is important to relax the strain induced by solidification or to homogenize the segregation so that domain walls can easily move.

Magnetic properties and microstructures of high heat-resistance Sm-Co magnets with high Fe and low Zr content 査読有り

Machida H., Fujiwara T., Fujimoto C., Kanamori Y., Sakakura K., Takezawa M.

AIP Advances 9 ( 12 ) 2019年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2019 Author(s). The magnetic properties and microstructures of 2-17 type Sm-Co magnets with high Fe and low Zr content were investigated. The developed magnet achieved maximum energy product, [BH]m of 34.5 MGOe, intrinsic coercivity, Hcj of 21.3 kOe and squareness of 73.3% at 25 °C. Temperature coefficients of remanent magnetic flux density, Br and Hcj were 0.034%/K and 0.28%/K respectively, which values were almost as same as the conventional Sm-Co magnets. Moreover, the developed magnets had high magnetization orientation. For XRD, it was found that Zr was preferentially substituted by Co-Co pair, this made interaction between Co and Co stronger, so that heat resistance was maintained. Magnetic domain structures were observed with a Kerr effect microscope, and then it was observed that the developed magnet had strong pinning force. In the microstructures, the developed magnet had 200∼500 nm cell size with Fe and Cu separated clearly. This led to large gap of domain wall energy which produces strong pinning force. Because the developed magnet had high magnetization orientation and large gap of domain wall energy, we achieved high magnetic properties and high heat resistance on the developed magnet.

DOI： 10.1063/1.5129805

Scopus

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Magnetic Domain Structures and Magnetic Properties of Lightly Nd-Doped Sm-Co Magnets with High Squareness and High Heat Resistance 査読有り

Machida H., Fujiwara T., Fujimoto C., Kanamori Y., Tanaka J., Takezawa M.

IEEE Transactions on Magnetics 55 ( 2 ) 2019年02月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 1965-2012 IEEE. The relationship between magnetic domain structures and magnetic properties of Nd-doped Sm(Fe, Cu, Zr, Co)7.5 was investigated. In the preparation process, slow cooling between sintering and solution treatment was employed to promote homogenization of microstructures. The developed magnet achieved a maximum energy product, [BH]m, of 33.8 MGOe and coercivity, Hcb, of 11.2 kOe at 25 °C, respectively. Moreover, B-H line at 150 °C was linear, which means that irreversible demagnetization does not occur even at 150 °C. Temperature coefficients of remanent magnetic flux density, Br, and intrinsic coercivity, Hcj, were 0.035%/K and 0.24%/K, respectively, as usual the conventional Sm-Co magnet. Magnetic domain structures were observed with a Kerr effect microscope with a magnetic field applied from 0 to-20 kOe, and then reverse magnetic domains were generated evenly from grain boundaries. Microstructures referred to as 'cell structures' were observed with a scanning transmission electron microscope. Fe and Cu were separated to 2-17 and 1-5 phases, respectively. Moreover, without producing impurity phases, Nd showed the same composition behavior with Sm in a cell structure.

DOI： 10.1109/TMAG.2018.2868969

Scopus

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研究調査委員会レポート：ナノスケール磁性体の構造・組織解析と創製調査専門委員会

竹澤昌晃

電気学会論文誌．　Ａ ( 一般社団法人電気学会 ) 139 ( 10 ) NL10_5 - NL10_5 2019年01月

Magnetic properties and crystal structure of high-purity Fe-(6,6.5,7) mass%Si alloys 査読有り

Matsuyama K., Sasaki I., Nakagawa S., Era H., Takezawa M., Horibe Y., Hata S., Kaidou C., Ogawa T., Kubo S.

2018 IEEE International Magnetic Conference, INTERMAG 2018 2018年10月

Change in Magnetic Domain Structure of Nd-Fe-B Sintered Magnets by Compressive Stress 査読有り

Takezawa M., Morimoto Y., Ejima J., Nakano Y., Araki T.

Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) 203 ( 1 ) 9 - 17 2018年04月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 Wiley Periodicals, Inc. To clarify the relationship between compressive stresses and demagnetization of Nd-Fe-B sintered magnets, we have examined the change in domain configuration by compressive stresses using a Kerr microscope. The magnetic domains of five kinds of Nd-Fe-B sintered magnets have been observed. The magnets have a coercivity of 0.8 MA/m to 1.4 MA/m and residual magnetic flux density of 1.3 T to 1.5 T. Irreversible demagnetization of Nd-Fe-B magnets with a low coercivity of 0.875 MA/m and high residual magnetic flux density of 1.41 T to 1.47 T have occurred from applying a compressive stress of 100 MPa. The compression-affected area is approximately 0.14%. The stress more than 50 MPa is needed to demagnetize Nd-Fe-B magnets. The amount of irreversible demagnetization depends upon the intensity of the compressive stress as well as the residual magnetic flux and coercive force of the magnets.

DOI： 10.1002/eej.23058

Scopus

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Influence of Misorientation Angle Between Adjacent Grains on Magnetization Reversal in Nd-Fe-B-Based Sintered Magnet 査読有り

T. Maki, R. Uchikoshi, R. Ishii, M. Natsumeda, T. Nishiuchi, M. Takezawa

Journal of the Magnetics Society of Japan 42 ( 2 ) 24 - 29 2018年03月

コールドクルーシブル溶解法で溶製した高純度Fe-3 mass%Si合金の磁気特性と機械的特性査読有り

中川翔太, 渡辺稜介, 佐々木巌, 竹澤昌晃, 堀部陽一, 波多聰, 開道力, 小川俊文, 恵良秀則

日本金属学会誌 82 ( 12 ) 476 - 483 2018年01月

記述言語：日本語掲載種別：研究論文（学術雑誌）

Magnetic properties and mechanical properties of high purity Fe-3 mass%Si alloy by cold crucible levitation melting was investigated. The raw material of the alloy made from electrolytic iron and pure silicon with a purity of 99.99 mass% and 99.999 mass% in amount of impurities excluding Fe and Si were suppressed to 90 ppm or less. In the magnetic property, the iron loss of the alloy was reduced to a third of 35H210, a silicon steel sheet of the same Si composition commercially. This reduction shows the effect of high purity. In the magnetic domain observation, the equal behavior as magnetic properties was observed. In mechanical property, it proved that the high purity Fe-3 mass%Si alloy was easy to draw because the elongation of the alloy was higher than the commercially available silicon steel sheet.

DOI： 10.2320/jinstmet.J2018008

CiNii Article

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Magnetic domain structure and demagnetization process of Nd-Fe-B anisotropic HDDR magnetic particles 査読有り国際誌

Takezawa M., Nagaishi T., Shimba K., Mishima C., Mitarai H.

2017 IEEE International Magnetics Conference, INTERMAG 2017 2017年08月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In recent years, there has been an increasing demand for Nd-Fe-B magnets. As they have a high maximum energy product (BH)max, they are used in the motors of hybrid vehicles.

DOI： 10.1109/INTMAG.2017.8007667

Scopus

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Magnetic domain control of amorphous ribbons for highly sensitive fluxgate sensors 査読有り

Miyata H., Yamamoto R., Morimoto Y., Takezawa M.

IEEJ Transactions on Fundamentals and Materials 137 ( 8 ) 466 - 469 2017年08月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 The Institute of Electrical Engineers of Japan. We observed the repeatability of changes in the magnetic domains of three types of amorphous ribbons. These ribbons were cut at their edges and annealed to control their domain structures. The domain change of the cut samples had good repeatability. Moreover, jitter noise in the fluxgate-sensor output for the amorphous ribbon decreased. A decrease in the magnetization-reversal jitter could be achieved through magnetic domain-structure control of the sensor core, which could improve the sensitivity of the fluxgate.

DOI： 10.1541/ieejfms.137.466

Scopus

CiNii Article

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Nd-Fe-B 系焼結磁石の圧縮応力による磁区構造変化査読有り

竹澤昌晃, 森本祐治, 江島潤, 中野善和, 荒木健

電気学会論文誌 A(基礎・材料・共通部門誌) 137 ( 7 ) 367 - 373 2017年07月

The high squareness Sm-Co magnet having Hcb=10.6 kOe at 150°C 査読有り

Machida H., Fujiwara T., Kamada R., Morimoto Y., Takezawa M.

AIP Advances 7 ( 5 ) 056223 全6ページ 2017年05月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 Author(s).The relationship between magnetic properties and magnetic domain structures of Sm(Fe, Cu, Zr, Co)7.5 magnet was investigated. The developed Sm-Co magnet, which is conducted homogenization heat treatment at ingot state, high temperature short time sintering and long time solid solution heat treatment showed the maximum energy product, [BH]m of 34.0 MGOe and the coercivity, Hcb of 11.3 kOe at 20°C respectively. Moreover, Hcb of 10.6 kOe at 150°C was achieved. Heat treated ingot has clear 1-7 phase in mother phase from optical microscope observation. Kerr effect microscope with magnetic field applied was used to investigate magnetic domain structure. Reverse magnetic domains were generated evenly but generation of them from inside grain were not observed. Cell structure was observed by scanning transmission electron microscope and composition analysis was conducted by energy dispersive X-ray spectroscopy. Cell size was approximately 150 ∼ 300 nm, Fe and Cu were clearly separated and concentrated to 2-17 phase and 1-5 phase respectively. Moreover, Cu concentration went up to 40 at% in 1-5 phase. That means the gap of domain wall energy between 1-5 phase and 2-17 phase was increased due to microstructure control by conducting heat treatment for compositional homogeneity.

DOI： 10.1063/1.4976334

Scopus

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ナノスケール磁性体の構造・組織解析と創製の研究動向

竹澤昌晃

電気学会論文誌 A(基礎・材料・共通部門誌) ( 電気学会 ) 137 ( 1 ) 26 - 27 2017年01月

Influence of misorientation angle between easy-axes of adjacent grains on magnetic domain propagation in Nd-Fe-B sintered magnet 査読有り

T. Maki, R. Uchikoshi, R. Ishii, T. Nishiuchi, M. Takezawa

Proceedings of the 24th International Workshop on Rare-Earth and Future Permanent Magnets and their Applications 24 637 - 640 2016年08月

Magnetics and optics research

Munekata H., Nakamura Y., Okamoto S., Sekiguchi K., Shiratsuchi Y., Takezawa M.

Japanese Journal of Applied Physics ( Japanese Journal of Applied Physics ) 55 ( 7 ) 2016年07月

Analysis of thermal demagnetization behavior of Nd–Fe–B sintered magnets using magnetic domain observation (共著) 査読有り

M. Takezawa, S. Ikeda, Y. Morimoto, H. Kabashima

AIP Advances 6 ( 5 ) 056021 2016年03月

The hysteresis properties analysis of Fe-4 wt% Si prepared by high purity metallurgy (共著) 査読有り

Z. Lei, T. Horiuchi, I. Sasaki, C. Kaido, M. Takezawa, S. Hata, Y. Horibe, T. Ogawa, H. Era

Journal of the Magnetics Society of Japan 40 ( 1 ) 8 - 12 2016年01月

Relationship between Microstructure and Magnetic Domain Structure of Nd-Fe-B Melt-Spun Ribbon Magnets(共著) 招待有り査読有り

M. Takezawa, H. Taneda, Y. Morimoto

Frontiers of Materials Science 9 ( 2 ) 206 - 210 2015年06月

Nd-Fe-B系焼結磁石の高温下における減磁過程の磁区観察

竹澤昌晃, 荻本紘史, 森本祐治

粉体および粉末冶金 ( 粉体粉末冶金協会 ) 62 ( 2 ) 67 - 71 2015年02月

Study on magnetic properties and domain structures of Fe-(5, 6) wt% Si alloys prepared with high purity metallurgy 査読有り

Lei Z., Horiuchi T., Mimura Y., Sasaki I., Kaido C., Takezawa M., Kubo S., Ogawa T., Era H.

2015 IEEE International Magnetics Conference, INTERMAG 2015 2015年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2015 IEEE.The hysteresis loss of silicon iron alloy is highly connected to the crystal defects caused by impurities, stress and so on, which contribute to a pinning effect of magnetic domain wall displacement and rotation, thus results in an increase of iron loss[1]. Therefore, highly pure silicon iron alloy is always desired among industries and researchers. In order to obtain high purity iron silicon alloy in the experiment, highly pure raw iron and silicon with a purity of 99.99 wt% were utilized, and a method called CCLM (Cold Crucible Levitation Melting), which is popular for high purity metallurgy of various materials, was introduced to melt raw materials. In CCLM furnace, during melting by electromagnetism induction heating, the melted alloy can avoid contacting the crucible because it is levitated by magnetic force simultaneously that can effectively reduce impurities of the alloy than other metallurgy.

DOI： 10.1109/INTMAG.2015.7156862

Scopus

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Magnetic domain observation of Nd-Fe-B sintered magnet at elevated temperature 査読有り

Takezawa M., Ogimoto H., Morimoto Y.

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 62 ( 2 ) 67 - 71 2015年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Magnetization reversal and its propagation in sintered Nd-Fe-B magnets were clearly observed at elevated temperature up to 150 °C using a Kerr microscope, image processing, and photo editing. Simultaneous magnetization reversal in several grains along the easy axis direction occurred at elevated temperature, and the extent of simultaneous magnetization reversal increased with temperature. This indicates that reduction in the coercivity of Nd-Fe-B sintered magnets at elevated temperatures is attributable to decrease in anisotropy and insufficient pinning of domain walls at grain boundaries.

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研究グループ紹介：九州工業大学大学院工学研究院先端機能システム工学研究系竹澤研究室

竹澤昌晃

電気学会論文誌. A ( The Institute of Electrical Engineers of Japan ) 135 ( 11 ) NL11_2 - NL11_2 2015年01月

Relationship Between Output of a Fluxgate Sensor and Magnetization Process of Its Core 査読有り

H. Miyata, R. Yamamoto, Y. Morimoto, M. Takezawa

IEEE Transactions on Magnetics 50 ( 11 ) 1 - 4 #4005804 2014年11月

Relationship between Sensor Output of a Fluxgate Magnetic Sensor and the Magnetic Domain Structure of its Core 査読有り

H. Miyata, Y. Morimoto, M. Takezawa

Journal of the Magnetics Society of Japan 38 ( 4 ) 169 - 173 2014年07月

Analysis of the Demagnetization Process of Nd-Fe-B Sintered Magnets at Elevated Temperatures by Magnetic Domain Observation Using a Kerr Microscope 査読有り

M. Takezawa, H. Ogimoto, Y. Kimura, Y. Morimoto

Journal of Applied Physics 115 ( 17 ) 17A733 2014年05月

Analysis of Magnetization Reversal Process of Nd-Fe-B Sintered Magnets by Magnetic Domain Observation Using Kerr Microscope 査読有り

M. Takezawa, Y. Kimura, Y. Morimoto and J. Yamasaki

IEEE Transactions on Magnetics 49 ( 7 ) 3263 - 3264 2013年07月

Easy Axis Orientation of Nd-Fe-B Melt-Spun Magnets Caused by Hot-Rolling 査読有り

Masaaki Takezawa, Toshio Mihara, Yuji Morimoto, Jiro Yamasaki, Masaaki Yagi

電気学会論文誌Ａ(基礎・材料・共通部門誌) 132 ( 10 ) 818 - 821 2012年10月

Magnetic Domain Observation of Nd−Cu-Diffused Nd-Fe-B Magnets with Submicron Grains by Kerr Effect Microscopy 査読有り

M. Takezawa, Y. Nagashima, Y. Kimura, Y. Morimoto, J. Yamasaki, N. Nozawa, T. Nishiuchi and S. Hirosawa

J. Appl. Phys. 111 ( 7 ) 07A714 2012年02月

Investigation of Easy Axis Orientation of Nd-Fe-B Melt-Spun Ribbons Produced by hot Rolling and Influence of Ti-C Addition 査読有り

M. Takezawa, Y. Nakanishi, Y. Morimoto, J. Yamasaki and M. Yagi

J. Appl. Phys. 111 ( 7 ) 07A703 2012年02月

高分解能Kerr効果顕微鏡を用いたNd-Fe-B系微細結晶粒磁石の磁区観察と磁化過程解析

竹澤昌晃

日本金属学会誌 ( 日本金属学会 ) 76 ( 1 ) 48 - 51 2012年01月

Magnetic Domain Observation of Nd-Fe-B Sintered Magnets at Elevated Temperatures by Using Kerr Microscope 査読有り

M. Takezawa, Y. Nagashima, Y. Morimoto and J. Yamasaki

IEEE Trans. Magn. 47 ( 10 ) 3256 - 3258 2011年10月

Magnetic Domain Observation of Nd-Fe-B Magnets with Submicron-Sized Grains by High-Resolution Kerr Microscopy 査読有り

M. Takezawa,N. Tani,Y. Nagashima,Y. Morimoto,J. Yamasaki,N. Nozawa,T. Nishiuchi and S. Hirosawa

J. Appl. Phys. 109 ( 7 ) 07A709.1 - 07A709.3 2011年03月

HDDR 磁粉の短時間ホットプレス法で得られたNd-Fe-B 系微結晶磁石の組織と保磁力

野澤宣介, 西内武司, 広沢哲, Hossein Sepehri-Amin, 大久保忠勝, 宝野和博, 竹澤昌晃, 丸子覚博, 谷奈緒美, 森本祐治, 山崎二郎

日立金属技報 27 34 - 41 2011年02月

Micromagnetic simulation of wall transition structures with self-induced helical anisotropy and their pinning effects 査読有り

Asada H., Kubo H., Yamasaki J., Takezawa M., Koyanagi T.

Journal of Physics: Conference Series 200 ( SECTION 4 ) 2010年09月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

A three-dimensional micromagnetic simulation has been performed to clarify the effect of self-induced anisotropy on domain wall behaviours, such as wall broadening and wall pinning, with wall transitions. Simulation results of the broadening of the domain wall with the transitions agree qualitatively with the Kerr microscope observation: for the wall transition which has a Bloch line between two C-shaped walls without a cap switch at each surface, the broadening of each Neel cap mainly occurs toward the opposite directions and the jog along the wall also becomes larger; for the wall transition which has a cap switch with a Bloch line, Neel caps still keep the same position after broadening. Details of pinning characteristics of the domain walls with the wall transitions by the self-induced helical anisotropy will also be presented. © 2010 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/200/4/042003

Scopus

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Recent Efforts Toward Rare-Metal-Free Permanent Magnets in Japan 査読有り

S. Hirosawa,T. Nishiuchi,N. Nozawa,T. Ohkubo,K. Hono,H. Sepehri-Amin,M. Takezawa,J. Yamasaki,S. Yamanuro,T. Tanaka,M. Okano and K. Sumiyama

Proceedings of the 21st Workshop on Rare-Earth Permanent Magnets and their Applications, Bled, Slovenia 21 187 - 192 2010年09月

Magnetic Domain Observation of Hydrogenation-Disproportionation- Desorption-Recombination Processed Nd-Fe-B Magnets with High- Resolution Kerr Microscope Using Ultraviolet Light 査読有り

M. Takezawa,K. Maruko,N. Tani,Y. Morimoto,J. Yamasaki,N. Nozawa,T. Nishiuchi and S. Hirosawa

Proceedings of the 21st Workshop on Rare-Earth Permanent Magnets and their Applications, Bled, Slovenia 21 51 - 54 2010年08月

光で見る磁石（磁性材料）の磁気的微細構造査読有り

竹澤　昌晃

電気学会誌 130 ( 8 ) 544 - 547 2010年08月

Magnetic domain observation of hydrogenation disproportionation desorption recombination processed Nd－Fe－B powder with a high-resolution Kerr microscope using ultraviolet light 査読有り

M. Takezawa,K. Maruko,N. Tani,Y. Morimoto,J. Yamasaki,T. Nishiuchi,S. Hirosawa

Jounal of Applied Physics 107 ( 9 ) 09A724.1 - 09A724.3 2010年04月

Effect of Surface Microstructure on Magnetization Process in Fe80.5Cu1.5Si4B14 Nanocrystalline Alloys 査読有り

M. Ohta,Y. Yoshizawa,M. Takezawa,J. Yamasaki

IEEE Transactions on Magnetics 46 ( 2 ) 203 - 206 2010年01月

Surface Domain Configuration of Nd-Fe-B Sintered Magnets Influenced by Underneath Magnetization 査読有り

M. Takezawa,Y. Ichihara,Y. Morimoto,J. Yamasaki

IEEE Transactions on Magnetics 45 ( 10 ) 4439 - 4442 2009年09月

磁気光学顕微鏡とその応用査読有り

竹澤　昌晃

電気学会論文誌A (基礎・材料・共通部門誌) 129 ( 9 ) 565 - 568 2009年09月

元素戦略プロジェクト「低希土類元素組成高性能異方性ナノコンポジット磁石の開発」の狙いと課題査読有り

広沢哲,西内武司,大久保忠勝,Li Wanfang,宝野和博,山崎二郎,竹澤昌晃,隅山兼治,山室佐益

日本金属学会誌 73 ( 3 ) 135 - 140 2009年03月

Domain Observation of Nd-Fe-B Sintered Magnets by Image Processing Using Liquid Crystal Modulator 査読有り

M. Takezawa,Y. Morimoto,J. Yamasaki

Proceedings of 20th International Workshop on Rare Earth Permanent Magnet & Their Applications 20 327 - 329 2008年09月

無方向性電磁鋼板における磁気特性方向依存性の検討査読有り

開道力,竹澤昌晃,山崎二郎,藤倉昌浩,茂木尚

Journal of the Magnetics Society of Japan 32 ( 3 ) 254 - 259 2008年05月

Magnetic Domains and Magnetization Process of Amorphous Granular (CoFeB)-SiO2 Thin Films 査読有り

M. Takezawa,A. Shiota,Y. Morimoto,J. Yamasaki,M. Munakata,M. Yagi

Jounal of Applied Physics 103 ( 7 ) 07E723.1 - 07E723.1 2008年02月

Domain Observation of Amorphous Wire with Large Diameter for Micro-Sensor and Micro-Motor Application 査読有り

M. Takezawa,T. Wada,Y. Morimoto,J. Yamasaki

International Journal of Applied Electromagnetics and Mechanics 25 ( 1-4 ) 189 - 192 2007年05月

Domain Observation Technique for Nd-Fe-B Magnet in High Magnetic Field by Image Processing Using Liquid Crystal Modulator 査読有り

M. Takezawa,T. Shimada,S. Kondo,S. Mimura,Y. Morimoto,T. Hidaka,J. Yamasaki

Jounal of Applied Physics 101 ( 9 ) 09K106.1 - 09K106.3 2007年05月

Effect of Nd-Rich Phase on c-Axis Orientation of Nd-Fe-B Melt-Spun Magnet and its Domain Structure 査読有り

M. Takezawa,K. Aiba ,H. Yasuda,Y. Morimoto,T. Hidaka,J. Yamasaki ,H. Kato ,M. Yagi

Journal of Magnetism and Magnetic Materials 310 ( 2 ) 2572 - 2574 2007年03月

Effect of Applied Magnetic Field on Anodic Oxidization of Aluminum for High-Aspect-Ratio Microfabrication 査読有り

M. Takezawa,T. Imagawa,J. Yamasaki,M. Yagi

Sensor Letters 5 ( 1 ) 293 - 295 2007年03月

Effect of Strain by Mechanical Punching on Nonoriented Si-Fe Electrical Sheets for a Nine-Slot Motor Core 査読有り

M. Takezawa,K. Kitajima,Y. Morimoto,J. Yamasaki,C. Kaido

IEEE Transactions on Magnetics 42 ( 10 ) 2790 - 2792 2006年10月

Domain Wall Pinning by Step-Like Thickness Change in Magnetic Thin Film 査読有り

M. Takezawa,K. Ejiri,J. Yamasaki,H. Asada,T. Koyanagi

Jounal of Applied Physics 99 08B701.1 - 08B701.3 2006年04月

Domain Observation of Amorphous Wire with Large Diameter for Micro-Sensor and Micro-Motor Application 査読有り

M. Takezawa,T. Wada,Y. Morimoto,J. Yamasaki

12th International Symposium on Interdisciplinary Electromagnetic, Mechanic & Biomedical Problems P3 - 3 2005年09月

Dynamic and Wide Field Domain Observation of Amorphous Ribbons with Longitudinal Kerr Effect Microscopy 査読有り

M. Takezawa,K. Kitajima,Y. Morimoto,J. Yamasaki

Journal of Applied Physics 97 10F701.1 - 10F701.3 2005年05月

Micromagnetic Study of Domain Wall Pinning Characteristics with Grooves in Thin Films 査読有り

H. Asada,H. Ii,J. Yamasaki,M. Takezawa,T. Koyanagi

Journal of Applied Physics 97 10E317.1 - 10E317.3 2005年05月

Asymmetric High-Frequnecy Carrier-Type Magnetic Field Sensor With Thin-Film Head Structure 査読有り

Masaaki Takezawa,Masatake Dobashi,Jiro Yamasaki

IEEE Transactions on Magnetics 40 ( 4 ) 2679 - 2681 2004年07月

Micromagnetic Study of Domain Wall-Pinning Characteristics With Step-Like Thickness Change in Thin Film 査読有り

H. Asada,Y. Hyodo,J. Yamasaki,M. Takezawa,T. Koyanagi

IEEE Transactions on Magnetics 40 ( 4 ) 2110 - 2112 2004年07月

Optimum Driving of Magnetostrictive Amorphous Wire Micro-Motor 査読有り

Masaaki Takezawa,Yuichi Ishizaki,Takashi Honda,Jiro Yamasaki

Journal of Magnetism and Magnetic Materials 272-276 e1735 - e1736 2004年05月

微細磁性体の磁区観察による磁化反転機構の検討査読有り

竹澤昌晃,森智礼,山崎二郎

日本応用磁気学会誌 28 ( 3 ) 384 - 387 2004年03月

Effect of Grain Size on Domain Structure of Thin Nonoriented Si-Fe Electrical Sheets 査読有り

M. Takezawa,Y. Wada,J. Yamasaki,T. Honda,C. Kaido

IEEE Transactions on Magnetics 39 ( 5 ) 3208 - 3210 2003年09月

Influence of domain wall structure on pinning characteristics with self-induced anisotropy 査読有り

H. Asada,Y. Wasada,J. Yamasaki,M. Takezawa,T. Koyanagi

Journal of Applied Physics 93 ( 10 ) 7447 - 7449 2003年05月

Domain Structure of Chemically Thinned non-Oriented Electrical Sheet 査読有り

M. Takezawa,J. Yamasaki,T. Honda,C. Kaido

Jounal of Magnetism and Magnetic Materials 254-255 167 - 169 2003年01月

Antiferromagnetic Coupled High-Frequency Carrier-Type Mangetic Field Sensor Using Ni-Fe/Fe-Mn Multilayer 査読有り

Masaaki Takezawa,Jiro Yamasaki

IEEE Transactions on Magnetics 38 ( 5 ) 3150 - 3152 2002年09月

強磁性/反強磁性結合を用いた高周波キャリア型薄膜磁界センサ査読有り

竹澤昌晃,福田亮介,山崎二郎

日本応用磁気学会誌 26 ( 5 ) 775 - 778 2002年05月

アモルファス薄帯における磁壁ピンニングの解析査読有り

浅田裕法,早田佳文,山崎二郎,竹澤昌晃,小柳剛

日本応用磁気学会誌 26 ( 4 ) 392 - 395 2002年04月

磁壁ピンニングを施した高周波キャリア型薄膜磁界センサヘッド用磁性膜の検討査読有り

竹澤昌晃,山崎二郎

日本応用磁気学会誌 26 ( 4 ) 559 - 561 2002年04月

GHz 帯における高周波キャリア型薄膜磁界センサの動作特性解析査読有り

竹澤昌晃,山口正洋,丹健二,荒井賢一,山川清志,大内一弘

日本応用磁気学会誌 25 ( 10 ) 1541 - 1546 2001年10月

Basic Load Characteristics of Magnetostrictive Amorphous Wire Micro-motor 査読有り

T. Sugino,M. Takezawa,T. Honda,J. Yamasaki

IEEE Transaction on Magnetics 37 ( 4 ) '2871 - 2873 2001年07月

Dynamic domain observation in narrow thin films 査読有り

M. Takezawa,J. Yamasaki

IEEE Transactions on Magnetics 37 ( 4 ) 2034 - 2037 2001年07月

無方向性珪素鋼板の厚みによる磁区構造変化査読有り

岩下聡,竹澤昌晃,本田崇,山崎二郎,開道力

日本応用磁気学会誌 25 ( 4-2 ) 903 - 906 2001年04月

リフトオフプロセスによる高周波キャリア型薄膜磁界センサ査読有り

菊池弘昭,網代紀行,山口正洋,荒井賢一,竹澤昌晃

日本応用磁気学会誌 25 ( 4-2 ) 975 - 978 2001年04月

Miniaturization of High-Frequency Carrier-Type Thin-Film Magnetic Field Sensor Using Laminated Film 査読有り

M. Takezawa,H. Kikuchi,M. Yamaguchi,K. I. Arai

IEEE Trans. Magn. 36 ( 5 ) 3664 - 3666 2000年05月

An evaluation of permeabiliity for striped thin films in the gigahertz range 査読有り

S. Yabukami,M. Takezawa,T. Uo,M. Yamaguchi,K. I. Arai,Y. Miyazawa,M. Watanabe,A. Itagaki,and H. Ando

Journal Applied Physics 87 ( 9 ) 5998 - 6000 2000年05月

Directivity and sensitivity of high-frequency carrier type thin-film magnetic field sensor 査読有り

M. Yamaguchi,M. Takezawa,H. Ohdaira,K. I. Arai,A. Haga

Sensors and Actuators A, Physical 81 102 - 105 2000年04月

高周波キャリア型薄膜磁界センサの小形化の検討査読有り

竹澤昌晃,網代紀行,山口正洋,荒井賢一,若生直樹,阿部岩男,辻真哉,板垣篤

日本応用磁気学会誌 24 ( 4-2 ) 727 - 730 2000年04月

Integration of High-Frequency Carrier-Type Thin-Film Magnetic Field Sensor with SmCo Thin-Film Bias Magnet 査読有り

M. Takezawa,Y. H. Kim,K. Ishiyama,M. Baba,M. Yamaguchi,K. I. Arai,N. Wako,I. Abe

IEEE Transaction on Magnetics 35 ( 5 ) 3682 - 3684 1999年09月

混合ブリッジ接続した高周波キャリア型薄膜磁界センサ査読有り

竹澤昌晃,大平祐史,馬場誠,山口正洋,荒井賢一,芳賀昭,若生直樹,佐藤尚之,阿部岩男

日本応用磁気学会誌 23 ( 4-2 ) 1621 - 1624 1999年04月

高周波キャリア型薄膜磁界センサの検出磁界分解能査読有り

荒井賢一,大平祐史,馬場誠,竹澤昌晃,山口正洋,芳賀昭

日本応用磁気学会誌 23 ( 4-2 ) 1617 - 1620 1999年04月

High Freguency Carrier Type Bridge-Connected Magnetic Field Sensor 査読有り

M. Takezawa,H. Kikuchi,K. Suezawa,M. Yamaguchi,K. Ishiyama,K. I. Arai

IEEE Transactions on Magnetics 34 ( 4 ) 1321 - 1323 1998年07月

Trial on-silicon micromagnetoelastic devices 査読有り

M. Takezawa,M. Yamaguchi,K. Ishiyama,K. I. Arai

Journal of Applied Physics 83 ( 11 ) 7303 - 7305 1998年06月

Micro Magnetic Thin-Film Sensor Using LC Resonance 査読有り

M. Takezawa,H. Kikuchi,K. Ishiyama,M. Yamaguchi,K. I. Arai

IEEE Transactions on Magnetics 33 ( 5 ) 3400 - 3402 1997年09月

微細形状磁性薄膜の高周波インピーダンス解析査読有り

菊池弘昭,竹澤昌晃,山口正洋,荒井賢一

日本応用磁気学会誌 21 ( 4-2 ) 789 - 792 1997年04月

LC共振を利用した高感度薄膜磁気センサの可能性査読有り

竹澤昌晃,中川英之,菊池弘昭,我妻成人,石山和志,山口正洋,荒井賢一

日本応用磁気学会誌 21 ( 4-2 ) 661 - 664 1997年04月

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