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

その他リンク： https://ci.nii.ac.jp/naid/130007976096

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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