• Title, Summary, Keyword: saturation magnetization

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Effect of Nucleation and Growth Dynamics on Saturation Magnetization of Chemically Synthesized Fe Nanoparticles

  • Ogawa, T.;Seto, K.;Hasegawa, D.;Yang, H.T.;Kura, H.;Doi, M.;Takahashi, M.
    • Journal of Magnetics
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    • v.16 no.3
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    • pp.308-311
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    • 2011
  • In order to obtain mono-dispersed Fe NPs with high saturation magnetization, quantitative analysis method to investigate the growth dynamics of the Fe NPs synthesized by a conventional thermal decomposition method has been developed. As a result, fast nucleation process promotes formation of ~4 nm of initial nucleus with a non-equilibrium phase, resulting in low saturation magnetization. And slow particle growth with atomic-scaled surface precipitation mode (< 100 atoms/($min{\cdot}nm^2$)) can form the growth layer on the surface of initial nucleus with high saturation magnetization (~190 emu/$g_{Fe}$) as an equilibrium a phase of Fe. Therefore, higher stabilization of small initial nucleus generated just after the injection of $Fe(CO)_5$ should be one of the key issues to achieve much higher $M_s$ of Fe NPs.

M-Zn (M = Sb, V, and Nb) Substituted Strontium Hexaferrites with Enhanced Saturation Magnetization for Permanent Magnet Applications

  • Sapoletova, Nina;Kushnir, Sergey;Ahn, Kyunghan;An, Sung Yong;Choi, Moonhee;Kim, Jae Yeong;Choi, Changhak;Wi, Sungkwon
    • Journal of Magnetics
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    • v.21 no.3
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    • pp.315-321
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    • 2016
  • M-Zn (M = Sb, V, Nb) substituted M-type strontium hexaferrites were prepared by a ceramic method. The phase composition, morphology and magnetic properties were studied by x-ray diffractometry, scanning electron microscopy and vibrating sample magnetometry. Saturation magnetization increases with a substitution up to 75.0 emu/g (2.5 % higher compared to unsubstituted hexaferrite) and then decreases with a further substitution. A coercive field of substituted hexaferrite powders with highest saturation magnetization is more than 3 kOe. Substituted strontium hexaferrite powders prepared in this work are a rare example of high $M_S$ compositions without doping rare-earth elements and would be a promising candidate for a permanent magnet application.

A Busbar Current Differential Relay with a Compensating Algorithm (보상 알고리즘을 적용한 모선보호용 전류차동 계전기)

  • 강용철;윤재성
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.53 no.4
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    • pp.214-220
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    • 2004
  • This paper describes a busbar current differential relay in conjunction with a current transformer(CT) compensating algorithm irrespective of the level of the remanent flux. The compensating algorithm detects the start of first saturation if the third-difference function of the current exceeds the threshold; it estimates the core flux at the first saturation start by inserting the negative value of the third-difference function of the current into the magnetization curve; thereafter, it calculates the core flux during the fault and compensates the distorted current using the magnetization curve. The algorithm estimates the correct secondary current irrespective of the level of the remanent flux and needs no saturation point of the magnetization curve. The proposed relay can improve not only security of the relay on an external fault with CT saturation but sensitivity of the relay on an internal fault; the relay can improve the operating speed on n internal fault with CT saturation. This paper concludes by implementing the relay into a digital signal processor based prototype relay.

$T^{3/2}$ Temperature Dependence of Magnetization of Amorphous $Fe_{80-x}Co_xB_{20}$ (비정질합금 $Fe_{80-x}Co_xB_{20}$ 자화값의 $T^{3/2}$ 온도 의존성)

  • Yu, Byeong-Du;Kim, Jong-O;Kim, Gyeong-Seop;Yu, Seong-Cho
    • Journal of the Korean Magnetics Society
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    • v.2 no.3
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    • pp.211-215
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    • 1992
  • The temperature-dependent saturation magnetization curves of amorphous $Fe_{80-x}Co_xB_{20}$ (8 ${\le}$ x ${\le}$ 40, the step of x is 8) alloys were measured using a vibrating sample magnetometer from 77 K up to 1000 K. Curie temperature and the Bloch coefficient were estimated from the saturation magnetization curves. The low temperature dependence of magnetization is in good agreement with Bloch relation, $M_s(T)$=$M_s(O)$ (1-$BT^{3/2}$ - ${\cdots}.$). The spin wave stiffness constant, tne range of the exchange interaction, and the probable atomic spin were calculated from the saturation magnetization values.

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Characteristic Analysis of a Flux-Lock Type SFCL Considering Magnetization Characteristic of Iron Core (철심의 자화특성을 고려한 자속구속형 초전도 사고전류제한기의 특성 분석)

  • Lim, Sung-Hun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.11
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    • pp.995-999
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    • 2007
  • We investigated the characteristics of a flux-lock type superconducting fault current limiter(SFCL) considering magnetization characteristic of iron core. The flux-lock type SFCL, like other types of SFCLs using the iron core, undergoes the saturation of the iron core during the initial fault time. Therefore, if the design to prevent the saturation of the iron core is considered, the effective fault current limiting operation can be achieved. Through the analysis for its equivalent circuit including the magnetization characteristic of the iron core, the limiting impedance of the flux-lock type SFCL was drawn. The magnetization currents and the limited currents of SFCL, which were dependent on the winding direction and the turns' ratio between two coils, were investigated from the short circuit experiment. It was confirmed that their experimental results agreed with the analysis ones.

The study on effects of porosity grain size, magnetization and anisotropy field on the properties of ferromagnetic resonance (다결정 Mg-페라이트의 기공율, 입경, 포화 자화 및 이방성 자기장이 강자성 공명 특성에 미치는 영향 연구)

  • 김진호;주승기;최덕균
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.1
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    • pp.97-102
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    • 1995
  • The ferromagnetic resonance properties of Mg ferrites which have various porosity grain size, and saturation magnetization are measured at one frequency. This allows a determination of the anisotropy field(Ha). The saturation magnetization multiplied by porosity is the resonance magnetic field. As the saturation magnetization increases, the linewidth decerases due to decrement of magnetic inhomogenity in sample. the porosity is a major factor broadening the linewidth for Mg ferrite when porosity is more thatn 6%, and the anisotropy field is dominant when porosity is less than 6%.

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Origin of the Initial Permeabiliy of Ni0.8-xZn0.2CoxFe2O4+δ Ferrite (Ni0.8-xZn0.2CoxFe2O4+δ조성 페라이트의 투자율 변화 기구)

  • 안용운;김종령;오영우
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.1
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    • pp.46-51
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    • 2004
  • The cause for the variation of the initial permeability according to the Co substitution of Ni-Zn ferrite used in the LC resonance filter for the power line communication is studied. The initial permeability decreases as the quantity of Co diminishes, and the saturation magnetization increases as the quantity increases. Because the sintering density and the microstructure of ferrite show little change, the variation of the initial permeability can't be explained by the density, microstructure nor the saturation magnetization factor. The magnetocrystalline anisotropy increases, similar with the saturation magnetization, as the quantity of Co increases. The increase of magnetocrystalline anisotropy value makes the domain wall energy grow, which leads to the decrease of the initial permeability, because there's linear law between the magnetocrystalline anisotropy and the domain wall energy. The resonance frequency to Co substitution moved to high frequency band, due to the close relationship with domain wall energy, Initial permeability decreaed a little with an increase of Co contents, but resonace frequency moved to high frequency band. as a result of that, when Co was added 0.05 mol, initial permeability and resonace frequency was 75 and 25 MHz respectively.

Characteristics Analysis of IPM Motor Considering Magnetic Saturation of Electrical Steel (IPM 모터 철심의 포화를 고려한 특성 해석)

  • Ha, Kyung-Ho;Ahn, Young-Jun;Na, Min-Su
    • Proceedings of the KIEE Conference
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    • pp.1031-1032
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    • 2011
  • This paper deals with the characteristics analysis of Interior Permanent Magnet Type Motor varying with magnetization curve of electrical steel interpolated with several method in the high field region. The data of magnetization curve of electrical steel given by the steel maker is not enough in order to analysis the characteristics by menas of FEM. Especially, the core in the bridge part have a severe saturation because the bridge width is narrow to reduce the flux leakage produced by the permanent magnet. This paper make the three kinds of magnetization curve by extrapolation and then the motor is analyzed by using these magnetization curve. The motor parameters are compared to explain the effects of magnetization curve.

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The Effects of Oxidation Conditions on the Magnetic Properties of Cu-Zn Ferrite Powder (산화 조건에 따른 Cu-Zn Ferrite분말의 자기적 특성)

  • Shin, K.H.;SaGong, G.
    • Proceedings of the KIEE Conference
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    • pp.222-224
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    • 1993
  • In this paper, The optimum oxidation conditions for the formation of Cu-Zn ferrite were investigated using precipitates obtained by the mixture of $CuCl_2{\cdot}2H_2O$, $ ZnCl_2$, $FeCl_3{\cdot}6H_2O$ and NaOH. The precipitates were prepared by coprecipitation method on various temperatures and oxidation conditions. The oxidation products were examined by SEM, XRD, and VSM. The particles obtained at 70($^{\circ}C$) were more spherical and fine than that of prepared at 25($^{\circ}C$), 50($^{\circ}C$), 60($^{\circ}C$), respectively. By $H_2O_2$ oxidation, the saturation magnetization of the powders was little influenced, But, by air oxidation the saturation magnetization of the powders was influenced intricately. According to our experimental data, the saturation magnetization of the powders increased with reaction time and was saturated at 9 hours.

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Structural and Magnetic Properties of perpendicular Recording Medium CoCrMo thin Film (수직자기기록매체 CoCrMo 박막의 구조와 자기적 성질)

  • 남인탁;홍양기
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.46-46
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    • 1988
  • Structural and magnetic properties of Co-Cr-Mo films were investigated in connection with sputtering conditions. Films were prepared using a convention RF sputtering system. X-ray diffractometry, scanning electron microscopy and transmission electron microscopy were employed to investigate structure properties. Vibrating sample magnetometry was used for coercivity and saturation magnetization measurements. Co-Cr-Mo films displayed reasonable values of perpendicular coercivity and saturation magnetization for perpendicular recording media and showed good perpendicular orientation of the hcp c-axis to the film surface. Perpendicular coercivity was strongly dependent upon substrate technique showed better c-axis orientation than hose using the stationary substrate. Co-Cr-Mo films of 2.9 at. % Mo content showed maximum perpendicular coercivity and saturation magnetization. The films deposited at lower Ar pressure showed good magnetic properties. There was no explicit relationship between the columnar structure and c-axis orientation. Co-Cr-Mo films was found to have suitable structural and magnetic properties for perpendicular recording media.

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