• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.22-28
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• 1992

Barium ferrite thin films were reactively deposited with Fe and BaO composite targets by a facing tergects sputtering unit. When thermally oxidized silicon wafers were used as substrates, minimum substrate heating of $750^{\circ}C$ was necessary for the perfect c-axis alignment in barium ferrite films. To lower the critical substrate temperature for the good c-axis alignment, such seed layers as ZnO, ${\alpha}-Fe_{2}O_{3}$ and ${\gamma}-Fe_{2}O_{3}$ were tested. The excellent c-axis algnment of BaM was obtained at a substrate temperature of $600^{\circ}C$ on ZnO seed layer whose (002) plane was parallel to the substrate surface. The magnetic properties of the BaM film showed saturation magnetization of 295 emu/cc, perpendicular coercivity of 1.7 kOe and squareness of 0.75. Optimum deposition rate of $230\;{\AA}/min$ was obtained with the composite target and this was 5 to 20 times higher than those of other investigators with oxide targets.

• Journal of the Korean Magnetics Society
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• v.2 no.2
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• pp.105-113
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• 1992

조성이 Mn$_{x}$Zn$_{1-x}$ Fe$_{2}$O$_{4}$ 훼라이트(x=0.75, 0.52)를 pusher type 연속 전기로를 이용하여 질소 분위기하에서 1360 .deg. C 로 3시간 동안 소결하여 얻어냈다. 본 연구에서는 스피넬 구조인 Mn-Zn 훼라이트의 FMR(Ferrimagnetic Resonance) 스펙트럼 특징과 초기투자율과의 상관성을 조사하고자 EPR X-band 스펙 트로미터를 이용 9.50 GHz의 microwave frequency에서 FMR 실험을 수행하였다. FMR 공명흡수선은 주 자기공명 흡 수선외에 낮은 자기장에서 약한 subsidiary 공명흡수선을 나타내는데 온도변화에 따른 주 자기공명 흡수선과 sub- sidiary 공명흡수선(제2, 제3 공명흡수선)의 세기, 공명선폭, g값 등의 온도 의존성을 연구함으로써 제2 공명흡수 선이 나타나는 원인을 분석하였으며, 자기공명 흡수선의 g값, 자기공명선 세기, 그리고 공명선폭과 초기투자율의 상관성을 연구하였다. 실험 결과 주 자기공명 흡수선의 g값, 자기공명선 세기, 공명선폭은 초기투자율 값과 밀접 한 관련이 있음을 확인할 수 있었다.었다.

• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.8-14
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• 1992

To improve the coercivity of ${\gamma}-Fe_{2}O_{3}$ particles. We have made cobalt ferrite epitaxial ${\gamma}-Fe_{2}O_{3}$ particles by crystallizing cobalt ferrite on the surface of ${\gamma}-Fe_{2}O_{3}$ particles. The coercivity of $Co_{x}Fe_{3-x}O_{4}$ which is conform to coating layer showed the most superior characteristic when the value of x was 1. On the formation of cobalt epitaxial ${\gamma}-Fe_{2}O_{3}$ particles, controlling reaction atmosphere as oxidation at. mosphere after non-oxidation atmosphere was the optimum condition to prepare cobalt epitaxial ${\gamma}-Fe_{2}O_{3}$ particles with superior magnetic properties. Epitaxial growth of cobalt ferrite on the surface of ${\gamma}-Fe_{2}O_{3}$ particles was accomplished at $90^{\circ}C$ for 30 minutes.

• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.15-21
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• 1992

Acicular ${\gamma}-Fe_{2}O_{3}$ particles were heated at $90^{\circ}C$ in alkaline solution containing mixed solution of dyadic metal with $Co^{+2}/Fe^{+2}$ ratio of 0.5. When cobalt content was increased, the coercivity of resultant product increased linearly, and surface area decreased. The cobalt ferrite was grown epitaxially on the surface ${\gamma}-Fe_{2}O_{3}$ crystal, and the increase of coercivity was attributed to the crystalline magnetic anisotropy of the cobalt ferrite which is conform to coating layer. We can expect superior magnetic properties above normal ratio of 2. The progress of reaction has an effect on coercivity of cobalt ferrite epitaxial iron oxide. The stability of temperature and the change om standin& of $Co-{\gamma}-Fe_{2}O_{3}$ was largely influenced by the composition of coating layer.

• Journal of Korean Electronics
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• v.4 no.11
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• pp.106-108
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• 1984

• Proceedings of the KIEE Conference
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• 1981.07a
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• pp.119-120
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• 1981

• Korean Journal of Materials Research
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• v.4 no.1
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• pp.117-124
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• 1994

The reduction of saturation magnetization in the Mg-Mn microwave ferrites was achieved by substituting the non-magnetic A1 ion for Fe ion. It is necessary for extending the operation frequencies that there is no change in other properties of the microwave ferrites. The electrical and magnetic properties are characterized where the composition of the ferrites studied was given by the general formula $(MgO)_{1.0}(MnO)_{0.1}(Al_xFe_{1.9-x}O_{2.85}$ with x ranging from 0.1 to 0.4. The saturation magnetization and the ferromagnetic resonance linewidth was decreased by the substituting amount of $Al_2O_3$. The value of coercive field was low enough over the composition of x=O.2 and the high squareness ratio was obtained all over the amount of substitution. It is feasible to select the proper application area with the combination of various properties ; that is, low coercive field, high squareness ratio, optimum saturation magnetization and ferromagnetic resonance linewidth.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1486-1496
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• 1993

The diamond wheel with superabrasive is required for mirror-like surface grinding of brittle materials. But the conventional dressing mothod can not apply to the diamond wheel with superabrasive. Recently electrolytic dressing method was developed for cast-iron bonded diamond wheel with superabrasive. This technique can take replace of lapping and polishing. Using the electrolytic dressing, the surface roughness of workpiece was improved largely and grinding force was very low and the continuity of the grinding force was also very improved. In this study, the purpose is the realization of mirror-like surface grinding of ferrite with electrolytic dressing of metal bonded diamond wheel. For application of ultraprecision grinding for brittle material, superabrasive wheel, air spindle and inprocess electrolytic dressing were used. In addition, the effects of pick current and pulse width on ground surface were investigated, and the suitable dressing conditions for ferrite were found out.

• Resources Recycling
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• v.5 no.2
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• pp.57-62
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• 1996

The regeneration of wastc piddlng acid from ironmaking industry produces Iron oxides as by products which are used for pigments and raw matcrial of ferrite. Thc impurilies level of iron axides for ferrile arc strictly regalated. Filtrat~on, adsorption medw technique, Fe leaching and ncutralizaiion wcre tried in order to remove silica impurities in the wasb pickling acid solution.

• Proceedings of the Korean Magnestics Society Conference
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• 1991.05a
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• pp.67-68
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• 1991