• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.66-72
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• 2012

The findings of ferromagnetic superconductor have attracted much attention not only for fundamental research to investigate how the antagonistic properties of ferromagnetism and superconductivity coexist peacefully but also for potential technological applications. Firstly, in order to help for understanding the ferromagnetic superconductor, I have explained the orbital and paramagnetic pair-breaking effects of magnetic field, which breaks the superconducting Cooper pairs. In addition to such effects of magnetic field, the singlet Cooper pairs become unstable upon going through the ferromagnetic materials by the proximity effect. The proximity effect occurs at the interface of thin films composing of superconductor and ferromagnet and leads to have very short penetration depth of Cooper pairs. However, a type of odd-frequency triplet in comparison with the singlet could be very stable and has a longer effective depth. It needs to be explored for the innovative spintronic devices. Finally, various ferromagnetic superconductors coexist and the lower-dimensional materials under the Quantum confinement effect have been introduced.

• Journal of Magnetics
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• v.19 no.1
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• pp.43-48
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• 2014

Magnetic materials with large coercive force and high squareness ratio are currently developing to meet an industrial demand. Since a ferromagnetic material has hysteresis characteristics, it is hard to demagnetize a ferromagnetic material precisely. In this paper, we describe deperm processes and conduct an analysis of residual magnetization of ferromagnetic material using the Preisach modeling with a two-dimensional finite elements method (FEM). From the results, it was shown that an exponential decrement form of deperm protocol is more efficient than a linear decrement form because of the demagnetizing field in the ferromagnetic material.

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.287.2-287.2
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• 2008

• Journal of the Korean Magnetics Society
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• v.15 no.6
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• pp.303-306
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• 2005

Effect of a ferromagnetic layer thickness on a narrow domain wall width is investigated. It is found that the narrow domain wall is formed in ferromagnetic/nonmagnetic/ferromagnetic multi layer structure with a loc at interlayer exchange coupling, and that the width of the narrow domain wall is affected by the ferromagnetic layer thickness. We performed micromagnetics simulations for the $Fe_1/Cr/Fe_2$ system with the local interlayer exchange coupling, with fixed thickness (20-nm) of $Fe_2$ layer and various $Fe_1$ layer thickness (1, 2, 4, and 6 nm). Consequently, we confirmed that the thinner the $Fe_1$ layer thickness, the thinner the width of the domain wall is formed, because of the surface energy nature of the interlayer exchange coupling.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.351-353
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• 1995

The physical origins of anomalous volume effect (Invar effect) and elastic effect (Elinvar effect) are critically examined. We found that, unlike the volume effect, the shear elastic properties are not much influenced by the ferromagnetic transition. This finding shows that the two anomalies originate from different physical origins, thus contradicting the conventional wisdom. We discuss the consequences of this finding in the light of recent experiments.

• Journal of the Korean Physical Society
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• v.73 no.12
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• pp.1884-1888
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• 2018

We have employed electron paramagnetic resonance spectroscopy and magnetization measurements in order to study the effect of Al-incorporation on the magnetic interactions in ZnO:Mn diluted magnetic semiconductors. Al-doping is shown to decrease the antiferromagnetic correlation and to increase the ferromagnetic interaction, which is attributed to the hydrogen-mediated ferromagnetic Mn complexes in our Mn-doped ZnO samples.

• Journal of Acupuncture Research
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• v.31 no.2
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• pp.21-30
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• 2014

Objectives : Manufacturing and manipulation techniques of acupuncture can be interpreted as an induced electromagnetic viewpoint, as proposed in previous study. Considering from this point of view, the magnetization of needles should be essential to enhance the electromagnetic effects during the behavior of the acupuncture needling. Methods : The current disposable needles are made of non-magnetic stainless steels, so ferromagnetic materials were searched as suitable substitutes. Meanwhile, at the practical view, stainless steels are very available for the several superior properties like as corrosion resistance, strength, etc., magnetic stainless steels were first investigated. Some types of them still preserved the ferromagnetic properties of iron, so trial needles were made with them. And then magnetization of them were followed. Results : Among the hundreds types of stainless steels, martensitic or ferritic ones are ferromagnetic. The needles made with these ferromagnetic wires were magnetized, and polarized by magnetizer, and their magnetic properties were improved. Moreover, in addition to the superiority of the magnetism, the electrical and thermal conductivities of them were even better than those of the current austenitic stainless steels. Conclusions : Through the developmental study based on the electromagnetic viewpoint, the magnetized and polarized acupuncture needles were completed. This means that these needles having improved magnetism can be used to improve the electromagnetic needling effects, and moreover, their superiorities in the electrical and thermal conductivities can also give another benefits in treatments of electrical or warm needling.

• Journal of Magnetics
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• v.19 no.3
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• pp.215-220
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• 2014

This study investigates the dynamic magneto-mechanical behavior of magnetization-graded ferromagnetic materials Terfenol-D/FeCuNbSiB (MF). We measure the dynamic magneto-mechanical properties as a function of the DC bias magnetic field ($H_{dc}$). Our experimental results show that these dynamic magneto-mechanical properties are strongly dependent on the DC bias magnetic field. Furthermore, the dynamic strain coefficient, electromechanical resonance frequency, Young's moduli, and mechanical quality factor of Terfenol-D/FeCuNbSiB are greater than those of Terfenol-D under a lower DC bias magnetic field. The dynamic strain coefficient increases by a factor of between one and three, under the same DC bias magnetic field. In particular, the dynamic strain coefficient of Terfenol-D/FeCuNbSiB at zero bias achieves 48.6 nm/A, which is about 3.05 times larger than that of Terfenol-D. These good performances indicate that magnetization-graded ferromagnetic materials show promise for application in magnetic sensors.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.950-953
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• 1999

Spin tunneling giant magnetoresistance effect was studied to utilize in the application of random access memory. Ferromagnetic/Insulator/Ferromagnetic films were sputtered on glass substrates and perpendicular current was applied. Measurements of magneto- resistance of the junction showed 8.6% of MR ratio. Voltage output depends on the magnetization directions of the write line and read line, thus enabling the system to be used as a random access memory

• Structural Engineering and Mechanics
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• v.88 no.2
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• pp.159-168
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• 2023

Cost-effective high precision hybrid elements are presented in a hierarchical form for dynamic analysis of plates. The costs associated with controlling the vibrations of ferromagnetic plates can be minimized by adequate determination of the amount of electric current and magnetic field. In the present study, the effect of magnetic field and electric current on nonlinear vibrations of ferromagnetic plates is investigated. The general form of Lorentz forces and Maxwell's equations have been considered for the first time to present new relationships for electromagnetic interaction forces with ferromagnetic plates. In order to derive the governing nonlinear differential equations, the theory of third-order shear deformations of three-dimensional plates has been applied along with the von Kármán large deformation strain-displacement relations. Afterward, the nonlinear equations are discretized using the Galerkin method, and the effect of various parameters is investigated. According to the results, electric current and magnetic field have different effects on the equivalent stiffness of ferromagnetic plates. As the electric current increases and the magnetic field decreases, the equivalent stiffness of the plate decreases. This is a phenomenon reported here for the first time. Furthermore, the magnetic field has a more significant effect on the steady-state deflection of the plate compared to the electric current. Increasing the magnetic field and electric current by 10-times results in a reduction of about 350% and an increase of 3.8% in the maximum steady-state deflection, respectively. Furthermore, the nonlinear frequency decreases as time passes, and these changes become more intense as the magnetic field increases.