• Title/Summary/Keyword: ferromagnetic

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A Study on the Deperm Protocols Considering Demagnetizing Field of a Ferromagnetic Material

  • Ju, Hye Sun;Won, Hyuk;Chung, Hyun Ju;Park, Gwan Soo
    • 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.

Ferromagnetic Resonance Observation of Martensitic Phase Transformation in Ni-Mn-Ga Ferromagnetic Shape Memory Films

  • Dubowik, J.;Kudryavtsev, Y.V.;Lee, Y.P
    • Journal of Magnetics
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    • v.9 no.2
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    • pp.37-39
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    • 2004
  • Polycrystalline Ni-Mn-Ga films have been deposited onto mica substrates held at 720 K by flash-evaporation method. At room temperature the films have a tetragonal structure with a = b = 0.598 and c = 0.576 nm typical for bulk $Ni_2MnGa$ below a martensitic transformation. Temperature measurements of ferromagnetic resonance reveal a martensitic phase transformation at 310 K. The transformation brings about a substantial decrease in the effective magnetization and a drastic increase in the ferromagnetic resonance linewidth due to a strong increase in the magnetic anisotropy in the martensitic phase.

Bistable Domain Wall Configuration in a Nanoscale Magnetic Disc: A Model for an Inhomogeneous Ferromagnetic Film

  • Venus D.
    • Journal of Magnetics
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    • v.10 no.3
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    • pp.113-117
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    • 2005
  • Some polycrystalline ferromagnetic mms are composed of continuously connected nanometer scale islands with random crystallite orientations. The nanometer perturbations of the mm introduce a large number of nearly degenerate local field configurations that are indistiguishable on a macroscopic scale. As a first step, this situation is modelled as a thin ferromagnetic disc coupled by exchange and dipole interactions to a homogeneous ferromagnetic plane, where the disc and plane have different easy axes. The model is solved to find the partial $N\acute{e}el$ domain walls that minimize the magnetic energy. The two solutions give a bistable configuration that, for appropriate geometries, provides an important microsopic ferromagnetic degree of freedom for the mm. These results are used to interpret recent measurements of exchange biased bilayer films.

Thermo-Magneto-Elastic Instability of Ferromagnetic Plates (강자성 판의 열-자탄성학적 불안정성)

  • 이종세;왕성철
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.153-160
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    • 2002
  • Based on a generalized variational principle for magneto-thermo-elasticity, a theoretical model is proposed to describe the coupled magneto-thermo-elastic interaction in soft ferromagnetic plates. Using the linearized theory of magneto-elasticity and perturbation technique, we analyze the magneto-elastic and magneto-thermo- elastic instability of simply supported ferromagnetic plates subjected to thermal and magnetic fields. A nonlinear finite element procedure is developed next to simulate the magneto-thermo-elastic behavior of a finite-size ferromagnetic plates. The effects of thermal and magnetic fields on the magneto-thermo-elastic bending and buckling is investigated in some detail.

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Ferromagnetic Resonance Frequency of Patterned Synthetic Antiferromagnet

  • Gong, Yo-Chan;Im, Sang-Ho;Lee, Gyeong-Jin
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • pp.57-58
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    • 2008
  • 외부 자기장이 spin-flip field보다 작은 조건 하에서 마이크로 사이즈로 패턴된 synthetic antiferromanet의 ferromagnetic resonance frequency를 표현할 수 있는 이론식을 유도했다. 또한 유도된 이론식을 통해 synthetic antiferromagnet의 기하학적, 자기적 성질이 ferromagnetic resonance frequency가 미치는 영향에 대해 연구했다.

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Development of Magnetized Ferromagnetic Stainless Steel Acupuncture Needle (강자성(强磁性) 스테인리스강(鋼) 자화침(磁化鍼)의 개발)

  • Hong, Do Hyun
    • 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.

Buckling of Ferromagnetic Plates in Thermal and Magnetic Fields (자기장과 온도장으로 재하된 강자성 판의 좌굴)

  • 이종세;왕성철
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.4
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    • pp.727-739
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    • 2002
  • Based on a generalized variational principle for magneto-thermo-elasticity, a theoretical model is proposed to describe the coupled magneto-thermo-elastic interaction in soft ferromagnetic plates. Using the linearized theory of magneto-elasticity and perturbation technique, we analyze the magneto-elastic and magneto-thermo-elastic instability of simply supported ferromagnetic plates subjected to thermal and magnetic fields. A nonlinear finite element procedure is developed next to simulate the magneto-thermo-elastic behavior of a finite-size ferromagnetic plates. The effects of thermal and magnetic fields on the magneto-thermo-elastic bending and buckling is investigated in some detail.

Effect of a Ferromagnetic Layer Thickness on a Narrow Domain Wall Width (좁은 자벽의 두께에 강자성층의 두께가 미치는 영향)

  • Lim, Ho-Tack;You, Chun-Yeol
    • 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.

Characterization and Analysis of Integrated RF Ferromagnetic Spiral Inductors (자성물질을 이용한 나선형 인덕터의 고주파 특성 분석)

  • Cha, S.Y.;Kim, G.B.;Jung, Y.C.;Choi, Y.S.;Cho, K.H.;Rieh, J.S.;Hwang, S.W.;Hyun, E.K.;Lee, S.R.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.109-111
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    • 2006
  • This paper presents characterization and analysis of integrated ferromagnetic inductors in RF regime. Two different materials (CoFe/NiFe) are used as ferromagnetic material. Systematic studies of the inductance (L), the Q-factor (Q) and the structure of the inductor have been performed.

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