著者

Y. Shiratsuchi T. V. A. Nguyen R. Nakatani

出版者

The Magnetics Society of Japan ( Nihon Jiki Gakkai )

雑誌

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

巻号頁・発行日

vol.42, no.6, pp.119-126, 2018-11-01 (Released:2018-11-01)

参考文献数

52

被引用文献数

3 5

---

Cr2O3 is a magnetoelectric antiferromagnet, and its antiferromagnetic domain state is controllable by the simultaneous application of magnetic and electric fields. In the 2000s, that is, more than 50 years since the discovery of the magnetoelectirc effect in Cr2O3, efforts were initiated apply this effect to engineering applications. In this article, we review the recent progress of the magnetoelectric control of the antiferromagnetic domain state and the related phenomena of Cr2O3, in particular, in an all-thin film system, an essential step to the application.

著者

X. Zhang J. Xia O. A. Tretiakov H. T. Diep G. Zhao J. Yang Y. Zhou M. Ezawa X. Liu

出版者

The Magnetics Society of Japan ( Nihon Jiki Gakkai )

雑誌

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

巻号頁・発行日

vol.47, no.1, pp.20-27, 2023-01-01 (Released:2023-01-01)

参考文献数

82

被引用文献数

1

---

Topological spin textures on artificial pinning landscape may show unique static and dynamic properties. Here, we computationally show that the helicity of frustrated skyrmions on an artificial square-grid obstacle pattern can be switched by a spin current pulse. The obstacle pattern is formed by defect lines with enhanced perpendicular magnetic anisotropy, which could protect the skyrmion from being annihilated at the sample edge. It is found that the skyrmion driven by a moderate current shows a circular motion guided by the boundary of the obstacle pattern, while it shows an almost straight motion toward the sample edge in the absence of the obstacle pattern. By applying a short pulse current to drive the skyrmion in a sample with the obstacle pattern, we find that the helicity of the skyrmion could be switched between Bloch-type configurations favored by the dipole-dipole interaction. Besides, we demonstrate the possibility of switching the helicity of an array of skyrmions on the square-grid obstacle pattern using the same method. Our results could be useful for the helicity control of topological spin textures, and may provide guidelines for building future helicity-based spintronic functions.

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

---

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

平田 絵梨 田中 健太 西村 一寛 井上 光輝

出版者

公益社団法人日本磁気学会

雑誌

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

巻号頁・発行日

vol.33, no.2, pp.114-117, 2009-03-01

参考文献数

2

被引用文献数

2 1

---

In order to quantitatively design of repulsive magnets type vibration limit switch, we have derived the vibration parameters which are expressed in vibration equation from experimental results. The vibration parameters are spring coefficient and damping coefficient at switch-on state. The vibration parameters and the structure parameter of switch were related quantitatively as linear and polynomial equations.

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

---

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

---

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

三澤 崇弘 田倉 哲也 佐藤 文博 佐藤 忠邦 松木 英敏

出版者

公益社団法人 日本磁気学会

雑誌

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

巻号頁・発行日

vol.37, no.3-1, pp.89-94, 2013-05-01 (Released:2013-05-23)

参考文献数

6

---

Many engineers have recently been developing battery chargers that have employed contactless power transmission techniques for consumer products. These have contributed to improving the convenience of charging batteries. We investigated methods of electromagnetic induction for transmission from several different types. The efficiency of power transmission was dependent on the quality factors of two coils and the coupling coefficient between them. Previous reports indicated that copper clad aluminum wire (CCAW) and magnetic-plated wire (MPW) can improve quality factors. We need to select these materials appropriately according to our individual needs in order to achieve highly efficient power transmission systems. Therefore, we examined the performance of three materials for power transmission coils in this research and found a method of selecting materials to construct a highly efficient system of transmission with a broad range of coupling coefficients.

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

---

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

開道 力

出版者

公益社団法人 日本磁気学会

雑誌

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

巻号頁・発行日

vol.34, no.3, pp.356-361, 2010-05-01 (Released:2010-05-28)

参考文献数

14

---

This paper discusses the possibility of realizing improvements in magnetic properties of non-oriented electrical steel sheets. In such sheets, a random {100} texture can increase flux densities and decrease iron losses, and the increase in flux density at 5000 A/m (B50) may be over 0.2 T, while decrease ratio of iron loss at 1.5 T and 50Hz (W15/50) may be more than 1/3. On the other hand, the improvement of iron loss at 1 T and 400Hz (W10/400) due to a random {100} texture may be little, but the texture can increase flux densities, and the increase in flux density at 800 A/m (B8),where motors are designed, may over 0.4 T. It is important to improve metallurgy and rolling technology in manufacturing process in order to realize the theoretical optimum magnetic properties of non-oriented electrical steel sheets.

著者

大友 祐一 薮上 信 加藤 和夫 小澤 哲也 荒井 賢一

出版者

公益社団法人 日本磁気学会

雑誌

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

巻号頁・発行日

vol.33, no.3, pp.283-286, 2009-05-01 (Released:2009-05-21)

参考文献数

5

被引用文献数

2 2

---

We developed a very sensitive high-frequency carrier-type magnetic-field sensor with a sub-pT resolution using a transmission-line-type sensor. Meander-type sensor elements using amorphous CoNbZr films (4μm in thickness), Cu conductor with a meander pattern (30 mm in length, 1.0 mm in width, 18 μm in thickness), and a ground plane were fabricated. We obtained a magnetic field resolution of 9.1×10-13 T/Hz1/2 at 1 Hz. The detectable magnetic field was limited by the 1/f noise. We detected a magnetocardiogram (MCG) signal of heartbeats with the sensor.

著者

小澤 哲也 山田 洋 佐藤 弘二 小島 健 薮上 信 小林 伸聖 中居 倫夫 荒井 賢一

出版者

公益社団法人 日本磁気学会

雑誌

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

巻号頁・発行日

vol.37, no.1, pp.1-7, 2013-01-01 (Released:2013-01-08)

参考文献数

12

被引用文献数

10

---

We report the results we obtained from applying a magnetic system to detect cracks using a thin film magnetic field sensor to measure the hole of aluminum. The thin film magnetic field sensor consisted of a coplanar line and amorphous CoFeSiB film. The main characteristic of the sensor is that the phase of the carrier signal changes when a magnetic field is applied. The sensitivity of the developed sensor was 70 deg./Oe. We used the thin film magnetic field sensor in an experiment to measure leakage magnetic flux from the surface of the aluminum while applying an AC magnetic field to the aluminum. The surface of the aluminum was scanned by an electric stage with a motor. The phase value of the sensor was converted to a voltage value, and then measured with a lock-in amplifier. As a result, the hole of aluminum was detected by measuring the distribution of the leak magnetic flux on the aluminum surface.

著者

薮上 信 加藤 和夫 加茂 芳邦 小澤 哲也 荒井 賢一

出版者

公益社団法人 日本磁気学会

雑誌

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

巻号頁・発行日

vol.32, no.4, pp.483-486, 2008-07-01 (Released:2008-07-18)

参考文献数

7

被引用文献数

1 1

---

We developed a very sensitive high-frequency carrier-type magnetic field sensor with a pT resolution using a transmission-line-type sensor. Meander-type sensor elements using amorphous CoNbZr films were fabricated. We obtained a magnetic field resolution of 3.0 x 10-12 T/Hz1/2 at 1 Hz. The detectable magnetic field was limited by the 1/f noise. We detected the magnetocardiogram (MCG) signal by using the sensor.

著者

内山 剛 山口 明啓 内海 裕一

出版者

公益社団法人 日本磁気学会

雑誌

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

巻号頁・発行日

vol.34, no.4, pp.533-536, 2010-07-01 (Released:2010-07-13)

参考文献数

7

---

In this experiment, we investigated noise characteristics of a pulse magneto-impedance sensor which is based on an amorphous magnetic wire with a pickup coil. For a helical static magnetization, the ac current i passing the wire induces a coil voltage Vc in the coil around the wire. The pulsed excitation, combining both high and low frequency harmonic, produces the voltage Vc with dc current biasing. We describe improvements of pulse excitation conditions for an amorphous magnetic wire to reduce magnetic noises. The relation between the time interval of a current pulse train T and magnetic noises was investigated. The magnetic noise is suppressed clearly when T is smaller than 1.5 μs for pulse width 10 ns. Under the optimal conditions, the rms noise of 1-cm-long an amorphous wire magneto-impedance sensor with 600 turns of the pickup was estimated as 1pT/Hz1/2M at 20 Hz∼500 Hz.

著者

N. Watanabe S. Matsusawa Y. Miyato H. Itozaki

出版者

(公社)日本磁気学会

雑誌

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

巻号頁・発行日

vol.37, no.3-2, pp.235-238, 2013-05-01 (Released:2013-05-23)

参考文献数

7

被引用文献数

2 6

---

We measured the high-resolution magnetic images using an STM-SQUID microscope that combines a high-Tc superconducting quantum interference device (SQUID) with a scanning tunneling microscope (STM). In the STM-SQUID microscope, the STM probe plays the important role of a flux guide and is responsible for tunneling current detection. Therefore, it is essential to investigate the probe itself in order to improve the magnetic image resolution. We optimized the electrochemical polishing condition to realize the fine probe with a tip radius of 50 nm or less. We fabricated the various shaped probes by controlling the voltage during sharpening. The tip radius of 50 nm or less was achieved when the probe tip was sharpened at the applied voltage of 30 V. We then measured the magnetic images of typical magnetic materials, such as a steel sample and nickel thin films, using the probe with a tip radius of 50 nm or less. The magnetic domain structures were observed clearly.

著者

N. Ota N. Gorjizadeh Y. Kawazoe

出版者

(公社)日本磁気学会

雑誌

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

巻号頁・発行日

vol.34, no.5, pp.573-578, 2010-09-01 (Released:2010-09-14)

参考文献数

31

被引用文献数

6 34

---

Several experiments have recently found room-temperature ferromagnetism in graphite-like carbon based materials. This paper offers a model explaining such ferromagnetism by using an asymmetric nano-graphene. Our first typical model is C48H24 graphene molecule, which has three dihydrogenated (-CH2) zigzag edges. There are several multiple spin states competing for stable minimum energy in the same atomic topology. Both molecular orbital and density function theory methods indicate that the quartet state (S=3/2) is more stable than that of doublet (S=1/2), which means that larger saturation magnetization will be achieved. We also enhanced this molecule to an infinite length ribbon having many (-CH2) edges. Similar results were obtained where the highest spin state was more stable than lower spin state. In contrast, a nitrogen substituted (-NH) molecule C45N3H21 demonstrated opposite results. that is, the lowest spin state (S=1/2) is more stable than that of highest one (S=3/2), which arises from the slight change in atom position.

著者

窪田 崇秀 児玉 謙司 中村 哲也 桜庭 裕弥 大兼 幹彦 永沼 博 高梨 弘毅 安藤 康夫

出版者

公益社団法人 日本磁気学会

雑誌

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

巻号頁・発行日

vol.34, no.2, pp.100-106, 2010-03-01 (Released:2010-03-24)

参考文献数

30

被引用文献数

1

---

We successfully fabricated L21-ordered Mn2VAl Heusler thin films and evaluated their ferrimagnetic properties by soft x-ray magnetic circular dichroism (XMCD). The buffer layers and annealing temperatures were varied to prepare the Mn2VAl films. We discovered that Mn2VAl could be ordered in an L21 phase well when it was deposited directly onto an MgO (001) single crystalline substrate. The maximum values of L21 and B2 long-range order parameters we obtained were about 0.5 for both phases for samples without a buffer layer, when substrates were heated at 500°C or 600°C. The saturation magnetization (Ms) for these samples was roughly 150 emu/cc. This is rather small compared to that expected from the ideal Slater-Pauling behavior, which might be due to the suppressed degree of L21 or B2 ordering. Ferrimagnetism in the Mn2VAl, ferrimagnetic coupling between Mn and V moments was clearly observed by using the XMCD technique in well-ordered L21-Mn2VAl film as has been predicted in theoretical investigations.

著者

R. Zhang T. Hamada S. Inagi Y. Kitamoto

出版者

(公社)日本磁気学会

雑誌

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

巻号頁・発行日

vol.37, no.3-2, pp.303-306, 2013-05-01 (Released:2013-05-23)

参考文献数

20

被引用文献数

3

---

Novel multifunctional superparamagnetic and optical nanohybrids are fabricated for biomedical applications. This architecture involves a silica core surrounded by a thin shell of FePt that is further covered with an outer shell of gold. Polyethyleneimine was utilized as a linker to bridge the FePt shell with the gold shell, which allowed 3-nm gold nanoparticle seeds to be loaded and a uniform gold shell to be formed. These gold and FePt doubly coated silica nanoparticles take advantage of the tunable resonance absorption in the visible and near-infrared (NIR) ranges and can be controlled by using an external magnetic field, which makes them very promising candidates for future biomedical applications.