• 한국자기학회지
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• 제13권1호
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• pp.1-5
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• 2003

조성비에 따른 (CoFe$_2$O$_4$)$_{1-x}$(Y$_3$Fe$_{5}$O$_{12}$)$_{x}$계의 분말을 산화물 합성법에 의하여 제작하였다. 120$0^{\circ}C$의 열처리로 합성된 분말을 X-선 회절기(XRD)로 측정한 결과에 의하면, 시료의 XRD 모형이 garnet과 Co 페라이트로 발생하는 peak으로 이루어짐을 확인할 수 있었다. 또한 주사전자현미경(SEM)을 이용하여 관측한 결과로 구조가 다른 두 개의 철산화물이 하나의 큰 입자로 결합되어 있음을 알 수 있었다. 두 개의 페라이트를 정확히 구분할 수는 없었으나, 구조가 다른 두 개의 페라이트가 하나의 입자로 잘 결합한 것을 확인할 수 있었다. Mossbauer분광기를 이용하여 측정한 결과는 garnet과 Co 페라이트에 의한 specturm의 면적비가 대부분의 흡수 spectrum을 이루고 있으나, 혼합물에 garnet과 Co 페라이트의 양이 충분한 경우에는 garnet에 있는 Fe 이온이 Co 페라이트의 다른 이온들과의 상호작용으로 d-site에 위치하는 흡수 spectrum이 두 개의 sub-spectrum으로 분리되는 것을 확인할 수 있었다. 이러한 결과는 XRD나 SEM의 관측결과와 같이 두 개의 시료가 하나의 입자로 잘 결합하였음을 의미하여, garnet의 철 이온이 Co페라이트의 이온과 상호작용으로 발생한 것이다. 섭동시료자화기(VSM)를 이용하여 측정한 조성비에 따른 시료의 포화자화 측정결과와 이론적으로 계산한 결과가 일치함을 알 수 있었다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.231.1-231.1
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• 2008

• Journal of Magnetics
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• 제10권3호
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• pp.80-83
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• 2005

Cobalt ferrite and garnet powders were grown using a conventional ceramic method in two different ways for understanding the magnetic interaction between structurally different materials. Structures of these powders were investigated by using an X-ray diffractometer (XRD) and the magnetic interaction between iron ions and the magnetic properties of the powders were measured by a $M\ddot{o}ssbauer$ spectroscopy and a vibrating sample magnetometer (VSM), respectively. The result of the XRD measurement showed that the annealing temperature higher than $1200^{\circ}C$ was necessary to grow a $(CoFe_2O_4)_{0.5}(Y_3Fe_5O_{12})_{0.5}$ powder. $M\ddot{o}ssbauer$ spectra for the powders grown separately and mixed mechanically consisted of sub-spectra of cobalt ferrite and garnet, however, powders annealed together had an extra sub-spectrum, which was related with the magnetic interaction between the grain surface of cobalt ferrite and the one of the garnet. In case of annealing the powders at the temperature large enough to crystallize them, raw chemicals became fine cobalt ferrite and garnet particles at first and then these fine particles were aggregated and formed large grains of ferrite powders. The result of the VSM measurement showed that the powders prepared at $1200^{\circ}C$ had the similar saturation magnetization and the coercivity regardless of the preparation method.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권4호
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• pp.153-158
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• 2003

This thesis deal with ferroelectric and ferromagnetic materials. PZT/Ferrite ceramics were made by the making process using PZT powder and garnet ferrite powder. PZT and ferrite are mixed as much 90%-10%, 50%-50%, and so on. After making samples, we are polishing samples until thickness is 0.1~0.2mm. We measured all kinds of samples in room temperature and applied magnetic field from -4500 to 4500 Oersted and conducted test of magnetical and electrical measurement using VSM and lpC resolution electrometer calibrated with RT66A pulsed tester. From this measurement, we can calculate tunability of these samples using C value obtained from P-E loop. As a result, it was able to measure magnetic characteristic when two matter had each other component ratio, and it was compound. However, it confirmed the possibility that was able to have ferroelectric characteristic with you in PZT 90% and ferrite 10%. Therefore, If this thing comes for PZT 50% and ferrite 50% have ferroelectric characteristic as him in a compound sample ore, can use this in an oscillator, supersonic waves detector in addition to a piezoelectric element. It may contribute to multipurpose of an element and demands such as a miniaturization of equipment, efficiency, reduce of a price which can use a characteristic of two components.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.78-81
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• 2002

This paper describes on the design structure and development temperature stable strip-line junction isolator operating in above resonance mode. Temperature characteristics of isolator depend on magnet, YIG(Yttium Iron Garnet) ferrite, and conductor etc. These require temperature stability and possible methods of compensation for the temperature dependent effects. In this paper, the analysis and measurement of the temperature characteristics were carried out for the material isolator prototype. The bandwidth of isolator was expended and the center frequency shift was reduced in temperature range of -20∼8O$^{\circ}C$.

• 한국전기전자재료학회논문지
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• 제15권12호
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• pp.1075-1078
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• 2002

This paper describes on the design structure and development of temperature stable strip-line function isolator operating In above resonance mode. Temperature characteristics of isolator depend on magnet, YIG(Yttium Iron Garnet) ferrite, and conductor etc. These require temperature stability and possible methods of compensation for the temperature dependent effects. In this paper, the analysis and measurement of the temperature characteristics were carried out for the material isolator prototype. The bandwidth of isolator was expended and the frequency shift at center was reduced in the temperature range of -20∼80$\^{C}$.

• 한국재료학회지
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• 제13권1호
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• pp.48-52
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• 2003

The substituted yttrium iron garnet systems $Y_{ 3-x}$/Gd$_{x}$X$0.2_{0.2}$ $Fe_{4.8}$ $O _{12}$ (x = 0.2, 0.4, 0.6) have been investigated by means of X-ray diffraction, Mossbauer spectroscopy and SQUID. The X-ray diffraction patterns at room temperature confirm the samples to have a single phase of the garnet structure over the whole composition range. The lattice constants of all the samples linearly change with increasing x due to the size of substituted ions in the dodecahedral sites. $Y_{3-x}$ $Gd_{x}$ X$Fe_{4.8}$ $In_{0.2}$ $O_{12}$ system which $Y_{3-x}$ ions are substituted with Gd$^{ 3＋}$ ions, the Mossbauer spectrum consists of three Zeeman sextets at room temperature, one due to the $Fe^{3＋}$ ions on the octahedral(a-) sites and the others due to the $Fe^{3＋}$ ions on the tetrahedral(d-, d'-) sites, respectively. From the hysteresis loop measured by means of SQUID over the whole composition range, the saturation magnetization $M_{s}$ and magnetic moments $\mu_{ B}$ per unit cell have been obtained. The increment of Gd-ion content causes $M_{s}$ and $\mu_{B}$ decrease while the increment of In-ion content does not.

• 전자통신동향분석
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• 제18권6호통권84호
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• pp.41-48
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• 2003

본 논문은 아이솔레이터의 소재 파라미터에 의한 삽입손실 영향에 대하여 서술하였다. 본 논문에서는 페리자성공명반치폭($\Delta$Η), 유전손실, 자계세기 그리고 포화자화에 대한 아이솔레이터 삽입손실의 관계를 알아 보았고, 또한 공진 아래 모드를 사용한 아이솔레이터의 온도안정화 연구 및 구조설계에 대하여알아 보았다. 아이솔레이터의 온도특성은 영구자석, YIG(Yttium Iron Garnet) 페라이트 그리고 공진기로사용되는 도체 등에 의한 변화에 대하여 본 논문에서는 실험시제품을 제작하여 측정 분석하였다. 측정결과 시뮬레이션 결과와 실험시제품 측정결과가 거의 일치하는 것을 알 수 있었다. 삽입손실 0.18~0.24dB, 반사손실 27dB, 아이솔레이션 27dB 그리고 대역폭 500MHz를 얻을 수 있었다. 이때 실험에 사용한 소재 파라미터는 포화자화 550G, 유전손실, $0.0004\Delta$Η20, 유전율 14로 하였다. 또한 온도안정화실험에서는 구조를 개선하여 온도안정화를 이루었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.533-536
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• 2003

YIG(Yttrium Iron Garnet) is one of the most widely used ferrites for microwave telecommunication. It used as a passive devices such as isolators and circulators. In order to reduce the insertion losses of these passive devices, it is very important to reduce magnetic loss of the ferrites. In general, the magnetic losses of ferrites is closely related to the microstructure of the ceramics. In the sintering of YIG, pores are easily trapped in grains and grain boundaries. These pores cause to increase magnetic losses of the sinterted bodies. In this paper, the effect of the $SiO_2$ addition on the microstructure was discussed. Increasing the $SiO_2$ addition, the grain size was reduced, which means that added acts as a grain-growth inhibitor. During the sintering, $SiO_2$ settled down on the grain boundaries, and drag the grain growth. Therefore, there is enough time for pores to move out. The relative density of YIG sintered at $1350^{\circ}C$ with 1 mol% $SiO_2$ addition was 99.6%. $\Delta$H of these samples was under 50 Oe.

• 한국세라믹학회지
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• 제38권12호
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• pp.1155-1161
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• 2001

YIG 페라이트는 마이크로파 RF 대역 통신 시스템, 이동통신, 위성방송 등의 정보산업과 각종 계측기기 등에 없어서는 안될 중요한 전자부품인 서큘레이터/아이솔레이터의 핵심소자로서 널리 사용되고 있다. 본 연구에서는 소결온도와 치환원소에 따른 서큘레이터/아이솔레이터용 YIG 페라이트의 미세구조와 전자기적 특성을 고찰하고자 하였다. Ca, V, In을 치환시킨 YIG 페라이트를 분무건조기를 사용하여 준구형 과립상태로 만들고, 일반적인 세라믹 제조 공정에 따라 125$0^{\circ}C$, 1275$^{\circ}C$, 130$0^{\circ}C$, 13$25^{\circ}C$에서 각각 소결하였다. 소결체는 XRD를 이용하여 상분석을 실시하였고, SEM을 이용하여 미세구조를 관찰하였으며, 전자기적 특성을 측정하기 위하여 VSM을 이용한 포화자화값 (4$\pi$ $M_{s}$) 측정과 FMR(Ferromagnetic Resonance)실험을 통한 자기공명반치폭($\Delta$H) 측정을 실시하였다. $Y_{1.6}$C $a_{1.4}$F $e_4$ $V_{0.7}$I $n_{0.3}$ $O_{12}$ 조성의 YIG 페라이트에 대한 전자기적 특성 측정 결과 130$0^{\circ}C$에서 소결한 YIG 페라이트가 높은 포화자화(4$\pi$ $M_{s}$) 값과 낮은 자기공명반치폭($\Delta$H)을 지닌 우수한 전자기적 특성을 나타내었다.다.을 나타내었다.다.