著者

D. Oyama N. Tsuyuguchi J. Hirama Y. Adachi J. Kawai

出版者

The Magnetics Society of Japan

雑誌

Journal of the Magnetics Society of Japan (ISSN:18822924)

巻号頁・発行日

pp.2307R004, (Released:2023-06-02)

参考文献数

25

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Ultra-low field (ULF) magnetic resonance imaging (MRI) is considered an innovative MRI technique that can be combined with magnetoencephalography (MEG). In this study, a 1-mT ULF-MRI system without a pre-polarization technique aiming at combining an MEG system is developed. The intensity of the static magnetic field B0 is decided considered to be 1 mT because of the limitation of the magnetic field exposed to our MEG sensor made of superconducting quantum interference devices (SQUIDs). A square-shaped (750 mm × 750 mm) B0-coil based on a Merritt-type configuration is fabricated. The inhomogeneity of B0 is less than 0.07 % in the ±125 mm area. Further, an induction coil is employed to detect the magnetic resonance signal instead of the SQUID sensors of the MEG to confirm the feasibility of realizing MRI measurement at 1 mT without the pre-polarization technique. Relaxation time measurements and MR imaging of a phantom made of a CuSO4 aqueous solution are performed. Reasonable longitudinal and transverse relaxation times are obtained, and clear shapes of the phantom are obtained using the gradient- and spin-echo pulse sequences with this ULF-MRI system. These results indicate the potential of the proposed 1-mT ULF-MRI to effectively integrate ULF-MRI and MEG systems without pre-polarization.

著者

菊川 信吾 磯村 悟 岩田 聡 塩見 繁 内山 晋

出版者

The Magnetics Society of Japan

雑誌

日本応用磁気学会誌 (ISSN:02850192)

巻号頁・発行日

vol.7, no.2, pp.83-86, 1983

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New bubble garnet films with orthorhombic anisotropy, (YTmGdBi)₃(FeGa)₅O₁₂, (YTmEuBi)₃(FeGa)₅O₁₂, (YTmSmBi)₃(FeGa)₅O₁₂ and (YTmLaBi)₃(FeGa)₅O₁₂, have been epitaxially grown on (110) GGG substrates. Although a large in-plane anisotropy <i>K</i>_p of 2∼4×10⁴ erg/cm³ is induced in YTmEu and YTmSm films, the uniaxial anisotropy <i>K</i>_u obtained is not large enough to be used for bubble materials. In YTmGd and YTmLa films, <i>K</i>_u is of almost the same magnitude as <i>K</i>_p with a value of 1.0∼1.5×10⁴ erg/cm³. The wall dynamics has been investigated by stripe domain transport method. For YTmLa films, the wall mobility μ is ∼22 m/sOe, the peak velocity <i>V</i>_p is ∼120 m/s and the coercive force <i>H</i>_c is ∼0.7Oe. These characteristics may be useful for current access devices.

著者

H. Tokumaru K. Arai S. Yoshimura K. Takizawa N. Uchida H. Yoshida

出版者

The Magnetics Society of Japan

雑誌

日本応用磁気学会誌 (ISSN:02850192)

巻号頁・発行日

vol.20, no.S_1_MORIS_96, pp.S1_323-328, 1996 (Released:2011-12-15)

参考文献数

5

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The requirements for optical tapes in an optical tape recording system using a rotating optical head are presented. Along with the requirements, the best structure for a magnet-optical (MO) tape was studied. As a result, a tri-layer structure was adopted for easy production and the tri-layerd MO tapes were experimentally fabricated. Performances and problems of an MO tape were experimentally investigated using these samples. And, the following results were obtained which realized performances equal to an optical disk using a thin polyethylene terephthalate (PET) substrate. (1) The incidence of the laser is from the tri-layer side to avoid the birefringence of the PET substrate. (2) Surface roughness of the PET substrate is below Ra = 7 nm. (3) Heat-resistance of PET substrate makes recording or erasing operations in excess of ten thousand times possible. (4) MO tape (width: 1/2 inch, thickness: 10 μm) was stable in terms of optical and magnetic properties under a tape tension of 0.5 kgw. (5) Sufficient tape tension is necessary to satisfy the requirement of flatness since MO tape has a large extent of curling.

著者

佐藤 靖之 浜本 正人 S. シュパイデル 岩田 聡 内山 晋

出版者

The Magnetics Society of Japan

雑誌

日本応用磁気学会誌 (ISSN:02850192)

巻号頁・発行日

vol.10, no.2, pp.133-136, 1986

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It is found that a large orthorhombic anisotropy is induced in (EuBi)₃Fe₅O₁₂ garnet films grown on (110) NdGG substrates. The Bi content is controlled by controlling the melt composition and the supercooling temperature. Gyorgy's parameter <i>B</i>=−2(<i>K</i>_u+<i>K</i>_p) increases linearly with the Bi content. The main part of <i>B</i> is found to be growth-induced. Gyorgy's parameter <i>A</i>=<i>K</i>_p−<i>K</i>_u is very small and almost independent of the Bi content. The growth- and stress-induced parts of <i>A</i> are found to be considerably large, but of opposite sign, and to compensate each other nearly completely, although their respective absolute values increase with increasing Bi content.<br>Magnetic properties of a (Eu_1.8 Bi_1.2) Fe₅O₁₂ film are obtained as follows: saturation magnetization 4π<i>M</i>_s = 1560 Gauss, uniaxial anisotropy <i>K</i>_u = 1.6 × 10⁵erg/cm³, in-plane anisotropy <i>K</i>_p = 1.6 × 10⁵erg/cm³, quality factor <i>Q</i> = 1.7, material length <i>l</i> = 0.06 μm and wall mobility μw = γ<i>Δ₀/<i>α</i> = 19 ms^-1. Such a film might be used as a 0.5 μm bubble material for current access devices.

著者

Y. Takamura Y. Stutler E. Matsushita K. Shinohara T. Suzuki S. Nakagawa

出版者

The Magnetics Society of Japan

雑誌

Journal of the Magnetics Society of Japan (ISSN:18822924)

巻号頁・発行日

vol.43, no.6, pp.120-124, 2019-11-01 (Released:2019-11-01)

参考文献数

26

被引用文献数

7

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We systematically investigated perpendicular magnetic anisotropy (PMA) in bilayers comprising ultrathin full-Heusler Co2FeSi (CFS) alloy and MgO as an insulator. The MgO layer was fabricated using two different sputtering techniques: reactive sputtering and radio-frequency sputtering. The characteristics of the layers fabricated using the different methods were compared. Irrespective of the MgO fabrication technique, the CFS/MgO bilayers exhibited PMA when the CFS surface was exposed to oxygen, which resulted in additional Fe–O bonds at the interface. Additionally, we characterized PMA in the bilayers while varying the substrate temperature TS for CFS sputtering. CFS samples that were 0.6-nm thick exhibited PMA when they were formed at TS as high as 300°C. The bilayer formed at 350°C exhibited in-plane magnetic anisotropy. Quantitative analysis of the magnetic anisotropy energy density revealed that the dominant magnetic anisotropy contribution in PMA differed between the bilayers formed at 300°C and 350°C. We expect these findings to be useful in the further development of high spin-polarized ferromagnetic electrodes containing PMA for next-generation spintronics devices.

著者

Y. Takamura Y. Stutler E. Matsushita K. Shinohara T. Suzuki S. Nakagawa

出版者

The Magnetics Society of Japan

雑誌

Journal of the Magnetics Society of Japan (ISSN:18822924)

巻号頁・発行日

pp.1911R004, (Released:2019-10-19)

参考文献数

26

被引用文献数

7

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We systematically investigated perpendicular magnetic anisotropy (PMA) in bilayers comprising ultrathin full-Heusler Co2FeSi (CFS) alloy and MgO as an insulator. The MgO layer was fabricated using two different sputtering techniques: reactive sputtering and radio-frequency sputtering. The characteristics of the layers fabricated using the different methods were compared. Irrespective of the MgO fabrication technique, the CFS/MgO bilayers exhibited PMA when the CFS surface was exposed to oxygen, which resulted in additional Fe–O bonds at the interface. Additionally, we characterized PMA in the bilayers while varying the substrate temperature TS for CFS sputtering. CFS samples that were 0.6-nm thick exhibited PMA when they were formed at TS as high as 300°C. The bilayer formed at 350°C exhibited in-plane magnetic anisotropy. Quantitative analysis of the magnetic anisotropy energy density revealed that the dominant magnetic anisotropy contribution in PMA differed between the bilayers formed at 300°C and 350°C. We expect these findings to be useful in the further development of high spin-polarized ferromagnetic electrodes containing PMA for next-generation spintronics devices.

著者

M. Tobise T. Ogawa S. Saito

出版者

The Magnetics Society of Japan

雑誌

Journal of the Magnetics Society of Japan (ISSN:18822924)

巻号頁・発行日

vol.41, no.3, pp.58-62, 2017-05-01 (Released:2017-05-01)

参考文献数

15

被引用文献数

14

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Metastable α”-Fe16N2 have attracted much interest as a candidate for rare-earth-free hard magnetic materials. To realize high coercivity, it is necessary to utilize not only the magnetocrystalline anisotropy but also the shape anisotropy of α”-Fe16N2 nanoparticles assemblies. An increase in magnetostatic couplings and intergranular exchange couplings among particles typically reduces the coercivity. Therefore, it is very important to evaluate the anisotropy and magnetic interactions among α”-Fe16N2 nanoparticles. We have examined the changes in morphology, structure and magnetic properties through the synthesis of α”-Fe16N2 nanoparticles from various materials such as α-FeOOH, ɤ-Fe2O3, and Fe3O4. The magnetic interactions were also estimated based on experimental results obtained by analysis of the rotational hysteresis loss of randomly oriented nanoparticles. Hc and Hkptc for the α”-Fe16N2 nanoparticle assemblies for different starting materials ranged from 2.2 to 1.1 kOe, and from 11 to 12 kOe respectively. Experimental results of the normalized coercive force and normalized switching field suggests that the existence of large magnetic interactions among α”-Fe16N2 nanoparticles.

著者

Yoshihisa Suzuki Sayoko Tanaka Shuichi Ichiura Hiroki Takao Satoru Ohnuki

出版者

The Magnetics Society of Japan

雑誌

Transactions of the Magnetics Society of Japan (ISSN:13467948)

巻号頁・発行日

vol.2, no.4, pp.290-293, 2002-10-01 (Released:2010-08-04)

参考文献数

6

被引用文献数

3

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OLYMPUS OPTICAL Co. Ltd., Hitachi Maxell Ltd. and SANYO Electric Co. Ltd. have developed a Magnet-Optical disk system, iD (Intelligent, Image) PHOTO disk as a next generation system for data storage. The iD PHOTO system is based on the AS-MO (Advanced Storage Magneto-Optical disk) and its media has a high capacity of 730 MB in a 50.8mm diameter single-sided disk. The storage capacity exceeds that of a CD (compact disc), while being the world's smallest rewritable optical disk.Considering its intended role as a portable application, it is important to evaluate its various characteristics under a variety of environmental conditions for its reliability. In this paper, we evaluated the recording and readout characteristics of the iD PHOTO disk under environmental temperatures ranging from -5°C to 60°C and under an accelerating condition. The obtained results proved the iD PHOTO disk to be a suitable recording medium for use as a mobile storage device with a high level of reliability and performance.

著者

浅沼 満

出版者

The Magnetics Society of Japan

雑誌

日本応用磁気学会誌 (ISSN:02850192)

巻号頁・発行日

vol.5, no.1, pp.1-5, 1981-02-28 (Released:2010-05-18)

著者

外村 彰

出版者

The Magnetics Society of Japan

雑誌

日本応用磁気学会誌 (ISSN:02850192)

巻号頁・発行日

vol.5, no.1, pp.6-11, 1981-02-28 (Released:2010-05-18)

参考文献数

28

被引用文献数

1 1

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Electron holography has recently made a remarkable progress due to the high coherence of an electron beam generated in a field emission electron microscope and almost reached the stage of practical reality.Holographic interference electron microscopy was realized which gives information on magnetization distribution of specimen. Interference fringes in a contour map were proved to be along the in-plane magnetic lines of force when the thickness was uniform and the magnetic field was closed in the specimen.

著者

能登路 淳 菊川 亮一 藤井 直樹 早川 元造 斉藤 皓彦

出版者

The Magnetics Society of Japan

雑誌

日本応用磁気学会誌 (ISSN:02850192)

巻号頁・発行日

vol.22, no.4, pp.657-660, 1998-04-15

参考文献数

6

被引用文献数

2 2

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The effects of tensile stress and strain on magnetization and magnetic domains in grain-oriented silicon steel sheets were investigated. The strain-magnetization properties of plastic deformation regions under stress showed peculiar characteristics. The magnetization increased with decreasing strain and, after reaching a peak value, decreased with decreasing strain. We observed Lancet domains in a sample after removing stress applied to a plastic deformation region. This phenomenon can be explained by changes in the domain structures, which were partly observed. The results obtained in this investigation can be applied to the nondestructive detection of fatigue in metallic magnetic materials.