• Title/Summary/Keyword: Soft magnetic

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Magnetic-vortex Dynamic Quasi-crystal Formation in Soft Magnetic Nano-disks

  • Kim, Junhoe;Kim, Sang-Koog
    • Journal of Magnetics
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    • v.22 no.1
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    • pp.29-33
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    • 2017
  • We report a micromagnetic numerical study on different quasi-crystal formations of magnetic vortices in a rich variety of dynamic transient states in soft magnetic nano-disks. Only the application of spin-polarized dc currents to a single magnetic vortex leads to the formation of topological-soliton quasi-crystals composed of different configurations of skyrmions with positive and negative half-integer numbers (magnetic vortices and antivortices). Such topological object formations in soft magnets, not only in the absence of Dzyaloshinskii-Moriya interaction but also without magnetocrystalline anisotropy, are discussed in terms of two different topological charges, the winding number and the skyrmion number. This work offers an insight into the dynamic topological-spin-texture quasi-crystal formations in soft magnets.

Manufacture of Permalloy Soft Magnets by Powder Injection Molding

  • W.Y. Jeung;Park, J.W.
    • Journal of Magnetics
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    • v.6 no.1
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    • pp.13-18
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    • 2001
  • Permalloy soft magnets have been produced by the powder injection molding process. Rheological characteristics of mixtures, debinding conditions, and the magnetic properties of permalloy after sintering have been investigated. A permalloy soft magnet with a permeability of 14200 could be obtained by preparing a mixture with a powder loading of 65.4 vol % and a PP/PEG binder systems solvent extraction, thermal debinding, and subsequent sintering at 1350$\^{C}$ in hydrogen. The permalloy soft magnet sintered in hydrogen had 95% of theoretical density and a magnetic induction of 13.2 kG in an applied magnetic field of 50 Oe.

Manufacturing of the Permalloy Soft Magnet by Powder Injection Molding Process

  • W. Y. Jeung;Park, J. W.
    • Proceedings of the Korean Magnestics Society Conference
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    • 2000.09a
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    • pp.217-227
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    • 2000
  • The permalloy soft magnet was produced by powder injection molding process. Rheological characteristics of mixtures, debinding conditions and the magnetic properties of permalloy after sintering ware investigated. The permalloy soft magnet with a permeability of 14200 could be obtained by preparing a mixture with a powder loading of 65.4 vol.% and PP/PEG binder system, solvent extraction, thermal debinding and subsequent sintering at 1350 $^{\circ}C$ in hydrogen. The permalloy soft magnet sintered in hydrogen showed a 95 % of theoretical density and a magnetic induction of 13.2 kG at the applied magnetic field of 50 Oe

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Research Trend of Soft Magnetic Composite Materials with High Energy Efficiency (고에너지효율 연자성 복합 분말 소재의 연구개발 동향)

  • Kim, Hwi-Jun
    • Journal of the Korean Magnetics Society
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    • v.21 no.2
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    • pp.77-82
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    • 2011
  • The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-to-particle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

Enhanced magnetic properties of FeCo alloys by engineering crystallinity and composition (FeCo의 결정성 및 조성 제어를 통한 자기 특성 향상)

  • Kim, Dan-Bi;Kim, Ji-Won;Eom, Nu-Si-A;Park, Seong-Heum;Im, Jae-Hong
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2018.06a
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    • pp.32.1-32.1
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    • 2018
  • Novel soft magnetic materials can be achieved by altering material properties such as morphology, composition, crystallinity, and grain size of soft magnetic alloys. Especially, magnetic properties (i.e., saturation magnetization, coarcivity) of soft magnetics are significantly affected by grain boundaries which act as a control of magnetic domain wall movement. Thus, we herein develop a two-step electroless plating method to control morphology and grain size of FeCo films for excellent magnetic properties. Accordingly, the chemical composition to control the degree of polarization of FeCo alloys was altered by electroless deposition parameters; for example, electrolyte concentration and temperature. The grain size and crystallinity of FeCo alloys was dramatically affected by the reaction temperature because the grain growth mechanism dominantly occurs at $90^{\circ}C$ where as the neucleation only happens at $50^{\circ}C$. By simply controlling the temperature, the micron-sized FeCo grains embedded FeCo film was synthesized where the large grains allow high magnetization originated from larger magnetic domain with low corecivity and the nano-sized grains allow excellent soft magnetic properties due to the magnetic correlation length.

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Dynamic Responses in Ultra-Soft Magnetic Thin Films (초 연자성 박막에서의 동적 자화 거동)

  • 정인섭
    • Journal of the Korean Magnetics Society
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    • v.4 no.1
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    • pp.1-6
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    • 1994
  • The magnetization dynamics was investigated by solving possible origins of overdamped susceptibility observed in ultra-soft magnetic amorphous thin films. The experimental high frequency spectrum and computational spectrum calculated from Gilbert's equation of motion were compared in order to find proper damping factor $\alpha{\approx}20$ and demagnetizing coefficients $D_{x}{\approx}D_{y}{\approx}D_{z}{\approx}0$ for ultra-soft magnetic films. A magnetization vortex mode was, then, proposed to explain the origin of the reversible susceptibility and other anomalies of the ultra-soft magnetic heterogeneous thin films. In this mode it is suggested that there occur, within the nanoscale structural features of the ultra-soft films, incoherent rotational spin motions that are highly damped by the energy transfer from short wavelength spin wave modes and local defect structure mode interactions.

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Degradation of Soft Magnetic Properties of Fe-Hf-N/Cr/SiO2 Thin Films Reacted with Bonding Glass (접합유리와 반응된 Fe-Hf-N/Cr/SiO2 박막의 연자기 특성 열화)

  • Je Hae-June;Kim Byung-Kook
    • Korean Journal of Materials Research
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    • v.14 no.11
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    • pp.780-785
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    • 2004
  • The degradation mechanism of soft magnetic properties of $Fe-Hf-N/Cr/SiO_2$ thin films reacted with a bonding glass was investigated. When $Fe-Hf-N/Cr/SiO_2$ films were annealed under $600^{\circ}C$ without the bonding glass, the compositions and the soft magnetic properties of Fe-Hf-N layers were not changed. However, after reaction with the bonding glass at $550^{\circ}C$, the soft magnetic properties of the film were degraded. At $600^{\circ}C$, the saturation magnetization of the reacted film decreased to 13.5 kG, and its coercivity increased to 4 Oe, and its effective permeability decreased to 700. It was founded that O diffused from the glass into the Fe-Hf-N layers during the reaction and generated $HfO_2$ phases. It was considered that the soft magnetic properties of the $Fe-Hf-N/Cr/SiO_2$ films reacted with the bonding glass were primarily degraded by the formation of the Fe-Hf-O-N layer of which the Fe content was below 60 $at\%$, and secondarily degraded by the Fe-Hf-O-N layer above 70 $at\%$.

Microstructure and Soft Magnetic Properties of Fe-6.5 wt.%Si Sheets Fabricated by Powder Hot Rolling

  • Kim, Myung Shin;Kwon, Do Hun;Hong, Won Sik;Kim, Hwi Jun
    • Journal of Powder Materials
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    • v.24 no.2
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    • pp.122-127
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    • 2017
  • Fe-6.5 wt.% Si alloys are widely known to have excellent soft magnetic properties such as high magnetic flux density, low coercivity, and low core loss at high frequency. In this work, disc-shaped preforms are prepared by spark plasma sintering at 1223 K after inert gas atomization of Fe-6.5 wt.% Si powders. Fe-6.5 wt.% Si sheets are rolled by a powder hot-rolling process without cracking, and their microstructure and soft magnetic properties are investigated. The microstructure and magnetic properties (saturation magnetization and core loss) of the hot-rolled Fe-6.5 wt.% Si sheets are examined by scanning electron microscopy, electron backscatter diffraction, vibration sample magnetometry, and AC B-H analysis. The Fe-6.5 wt.% Si sheet rolled at a total reduction ratio of 80% exhibits good soft magnetic properties such as a saturation magnetization of 1.74 T and core loss ($W_{5/1000}$) of 30.7 W/kg. This result is caused by an increase in the electrical resistivity resulting from an increased particle boundary density and the oxide layers between the primary particle boundaries.

Characteristics of Electromagnetic Wave Absorber Sheet for 2.4 GHz Wireless Communication Frequency Bands Using Fe Based Alloy Soft Magnetic Metal Powder (Fe-계 연자성 금속분말을 이용한 2.4 GHz 대역 무선통신용 전파 흡수체의 특성 평가)

  • Kim, ByeongCheol;Seo, ManCheol;Yun, Yeochun
    • Korean Journal of Materials Research
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    • v.29 no.9
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    • pp.532-541
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    • 2019
  • Information and communication technologies are developing rapidly as IC chip size becomes smaller and information processing becomes faster. With this development, digital circuit technology is being widely applied to mobile phones, wireless LANs, mobile terminals, and digital communications, in which high frequency range of GHz is used. In high-density electronic circuits, issues of noise and EMC(Electro-Magnetic Compatibility) arising from cross talk between interconnects or devices should be solved. In this study, sheet-type electromagnetic wave absorbers that cause electromagnetic wave attenuation are fabricated using composites based on soft magnetic metal powder and silicon rubber to solve the problem of electromagnetic waves generated in wireless communication products operating at the frequency range of 2.4 GHz. Sendust(Fe-Si-Al) and carbonyl iron(Fe-C) were used as soft magnetic metals, and their concentrations and sheet thicknesses were varied. Using soft magnetic metal powder, a sheet is fabricated to exhibit maximum electromagnetic attenuation in the target frequency band, and a value of 34.2dB(99.9 % absorption) is achieved at the target frequency.

Influence of the tempering and magnetic annealing on soft magnetic properties for the KM35F alloy (템퍼링 및 자장열처리가 KM35F 합금의 연자성 특성에 미치는 영향)

  • Park, Byung-Ki;Jeon, Yong-Sik;Kim, Dong-Soo
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1240-1243
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    • 2008
  • The tempering and magnetic annealing are used to improve the soft magnetic properties such as initial permeability coercivity and core loss of the KM35F alloy. The first heat treatmentis performed at the temperature less than the curie temperature of the KM35F alloy to remove the thermal stress for few hours in nitrogen atmosphere. The second stage heat treatment is performed the magnetic annealing at $500{\sim}800^{\circ}C$ for few hours in nitrogen atmosphere, and then quenching to room temperature in absence of oxygen. Finally, magnetic properties of the thermally treated KM35F alloy are investigated for application as a soft magnetic material of the ISO solenoid valve core and plunger.

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