• 한국자기학회지
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• 제4권2호
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• pp.94-99
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• 1994

다결정 Mg-ferrite에 있어서 초기 복소 투자율과 소결체내 기공율과의 관계에 대한 연구 논문으로서, $MgFe_{2}O_{4}$의 초기 투자율의 주파수 특성에 있어서 입경이 큰 소결체를 제외 하고 Snoek 이론이 잘 적용되었다. 50-80[MHz] 주파수 범위내에서 자구 회전에 따른 초기 투자율의 실수부, $\mu$'이 1이되는 주파수가 관찰되었다. 다결정 Mg-ferrite에 있어서 초기복소 투자율과 소 결체내 기공율과의 관계부터 이방성 자기장이 주 성분일 것으로 사료되는 미지의 내부 자기장을 계 산한 결과 약 100[Oe]로서 조사되었으며, 이는 단결정 $MgFe_{2}O_{4}$ 시편으로부터 보고되고 있는 이방성 자기장의 약 1/2로 나타났다. 이러한 차이는 소결체 시편내 포함되어 있는 자벽의 영향 에 주로 기인함을 알 수 있다.

• 전기학회논문지P
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• 제51권2호
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• pp.82-86
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• 2002

A series of $Ni_xZn_yFe_{3-x-y}O_4$ films were prepared by spin-spray ferrite plating on glass substrates from aqueous solution at $90[^{\circ}C]$. The magnetic properties in terms of contents of Ni and Zn in the plated films are presented. All the films are polycrystalline with spinel structure. At x+y=0.58, the film presents preferential orientation. As composition of y in the films increases grain size and void in the films increases, while saturation magnetization and coercive force of the films decrease.

• 열처리공학회지
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• 제12권2호
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• pp.157-165
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• 1999

Grain size of steels is one of the most important parameters which influence yield strength and fracture toughness. Ultrasonic wave propagating in polycrystalline materials is mostly attenuated by scattering at grain boundary. Effect of ultrasonic attenuation on average ferrite grain size of carbon steels with tensile strength $40{\sim}60kgf/mm^2$ consisting of multi phases such as ferrite + pearlite and ferrite + pearlite + bainite was evaluated. The attenuation of these steels rapidly increased with average ferrite grain diameter. Average ferrite grain diameter ($D_{av}$, ${\mu}m$) could be expressed as $1.79+22.97*a^{1/2.03}$, where a is attenuation with unit of nepers/cm. From this study, it was confirmed that nondestructive ultrasonic method could be used in measuring average ferrite grain size indirectly.

• 한국안광학회지
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• 제7권1호
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• pp.35-38
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• 2002

자외선과 전자파를 동시에 차단하는 선글라스렌즈를 제작하기 위하여 유리기판 위에 자성재료인 페라이트 박막을 페라이트 도금법으로 제작하였다. 이들은 모두 스피넬 구조의 단일상임을 확인할 수 있었으며, 육안으로 관찰할 때 거울면과 같은 광택을 가졌으며, 손톱으로 긁었을 때 흠집이 생기지 않는 경도를 보였다. 페라이트는 400nm 부근에서부터 급격히 투과율이 떨어져 자외선을 차단하는데 효과적인 양상을 보이고 있다. 타사제품과 비교하여 자외선 차단효과는 크게 떨어지지 않으며, 전자파 차단효과가 있는 페라이트를 코팅한 선글라스를 착용함으로서 유해전자파와 자외선을 차단하는 효과를 얻을 수 있을 것이다.

• The Korean Journal of Ceramics
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• 제6권4호
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• pp.405-407
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• 2000

Polycrystalline films of Ni- and Co-ferrites films are prepared from aqueous solution at $90^{\circ}C$ by ferrite plating, which are subjected to Fe$^57$ conversion electron Mossbauer spectroscopy in backscatter mode. The average angle of Fe spins relative to the film plane is evaluated as 18 degree and 82 degree for the Ni- and Co-ferrite films, respectively, indicating a prominent magnetic anisotropy parallel and perpendicular to the film plane. It was also verified by the magnetization measurements.

• 한국세라믹학회지
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• 제32권2호
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• pp.163-170
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• 1995

Sample size effect on ferromagnetic resonance (FMR) in polycrystalline MgFe2O4 has been investigated. The signal intensity (SI), resonance field (Hres) and line width (ΔH) were found to increase proportionally to r3 with the increase of sample radius. The r3-depencence of SI means the complete penetration of rf-field into the sample, and the broadening of ΔH due to the sample size appears to be closely related to the amount of scattering sources like pores. Meanwhile, the values of Hres (0) and ΔH (0) obtained by extrapolating the data of Hres (r) and ΔH (r) measured at several sizes to r=0, were in good agreement with those calculated using the Schlomann's equations for internal field and ΔH, respectively. This result indicates that the discrepancy between the measured FMR parameters and those calculated by Schlomann's equation could be ascribed to the effect of sample size. Thus it is suggested that the size effect on FMR should be removed for the analysis of the FMR parameters. Meanwhile, our result for the size dependance of ΔH was found to be contradictory to those reported by Dionne, where ΔH 1/r at a given surface roughness. This discrepancy appears to arise from the difference in the definition of reading the line width.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1999년도 추계연구발표회 논문개요집
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• pp.36-37
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• 1999

• 한국세라믹학회지
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• 제29권7호
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• pp.539-543
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• 1992

The continuous growth method was developed for Mn-Zn Ferrite single crystals. It is a new process that the polycrystalline MnχZn1-χFe2O4 raw materials are supplied continuously from the powder feeding system to the crucible heated by R.F. induction and melted in the crucible, and after the single crystals seed is attached to crucible's hole, the crystals are pulled downward with rotation. Growing the crystals by using the growth method different from the conventional Bridgman or Floating Zone method, we defined the factors having effect on the crystal growing through the pre-experiments. They are temperature distribution in the crucible, melt velocity according to its height, wettability between the crucible's bottom and melt. Therefore, Mn-Zn Ferrite single crystals were to be grown by attaining the appropriate melt height in the crucible, powder feeding rate, temperature gradient between the crucible and interface, crystal growing speed, and this method was confirmed to have possibility for single crystal growing.

• 한국재료학회지
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• 제14권9호
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• pp.655-658
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• 2004

Lithium ferrites are a low-cost material which have been prominent in the high frequency core industry because of their excellent temperature performance and high squareness ratio. In order to develope the lithium ferrites with the high squareness and low coercive force, the ferrites of $Li_{0.48}Bi_{0.02}Ni_{0.04}Fe_{2.46-x}O_4$ were investigated the by varying composition, temperature and frequency. Electric loss of the Li-ferrite was lowered with the substitution of $Mn_{2}O_3$. The addition of $Mn_{2}O_3$ increased the magnetic induction (Bm&Br) but decreased the coercive force (Hc) and the squareness ratio (R=Br/Bm). Also, the Br value was stable at environmental temperature variation.

• 한국전기전자재료학회논문지
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• 제11권8호
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• pp.652-657
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• 1998

We have performed spin-spray ferrite plating of $Fe{_3}{-X}-Ni_XO_4$(X=0.17~0.26) films in the temperature region $T=80~95[^{\circ}C]$. A reaction solution and an oxidizing solution were supplied to a reaction chamber by supply pump. The solubility limit of Ni increases as the substrate temperature increase, from X=0.17 at $80[^{\circ}C]$ to X=0.26 at $95[^{\circ}C]$. All the films are polycrystalline with no preferential orientation, and the magnetization exhibits no definite anisotropy. Grain size in the films increases as X increases, reaching $0.87[\mu{m}]$ at X=0.26.