• 한국자기학회지
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• 제5권5호
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• pp.702-709
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• 1995

In this paper we review recent work in our laboratory on nanocomposite CoSm-based films including CoSm with Cr underlayer (CoSm//Cr), exchange-coupled magnetic films consisting of CoSm and FeCo layers (CoSm/FeCo), and CoSm multilayers with nonmagnetic spacing layers of SmO (CoSm/SmO). The emphasis is on detailed investigations of microstructure and magnetic properties for CoSm//Cr films, exchange-spring effects for CoSm/FeCo films, and interlayer effects for (CoSm/ SmO) multilayers.

• 한국자기학회지
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• 제9권6호
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• pp.312-320
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• 1999

RF 마그네트론 스퍼터링으로 제조한 SmCo/Cr 박막의 스퍼터 제조조건에 따르는 자기적 특성에 관하여 연구하였다. Sm 조성이 약 20 at %이고 Cr(50 nm)/SmCo(40 nm, 50W, 20mT)/Cr(150 nm, 100W, 30 mT)인 조건에서 제조한 시편에서 3.2 kOe의 최대 보자력을 얻었다. SmCo/Cr의 보자력은 하지층 표면거칠기와 SmCo의 조성에 크게 영향을 받았다. Cr 하지층의 거칠기는 Ar 분압과 두께가 증가할수록 증가하고 이는 SmCo 입자의 고립을 증가시켜 보자력이 증가된다. 본 SmCo 박막 증착시 사용한 RF 투입전력 및 Ar 분압은 SmCo의 조성을 변화시키며 최적의 조성(약 20 at.%Sm)에서 최대 보자력을 보인다. 또한 RF 파워 증가나 Ar 분압 증가에 의해 생긴 Cr 하지층의 표면거칠기, 치밀하지 않은 주상 계면구조등의 결함이 자구벽 이동을 방해하여 보자력 증가에 영향을 끼친다.

• 한국자기학회지
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• 제13권5호
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• pp.198-203
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• 2003

경자성박막을 이용한 자기임피던스센서의 바이어스 자계 인가의 유용성을 알아보기 위해서, SmCo 경자성박막의 조성에 따른 자기적 특성과 이 박막이 아몰퍼스 CoZrNb 연자성박막에 미치는 바이어스 효과에 대하여 조사하였다. 아몰퍼스상을 가지는 SmCo 경자성박막의 포화자화는 Sm 조성이 증가함에 따라 감소하였으며, 보자력은 Sm 조성의 증가에 따라 증가하다가 28 at% 부근에서 약 500 Oe를 나타낸 후 다시 감소하였다. SmCo 박막에 의해서 발생된 바이어스 자계가 CoZrNb 박막에 미치는 효과는 자화곡선과 투자율의 측정, 그리고 자구관찰을 통하여 조사되었다. MI센서로 사용이 가능한 3${\times}$0.5 $\textrm{mm}^2$ 크기의 박막시료에 있어서, 약 60 Oe의 바이어스 자계가 얻어졌으며, 센서의 감도를 최적화하기에 충분한 바이어스 자계를 경자성박막을 이용하여 발생시킬 수 있음을 입증하였다.

• 한국전기전자재료학회논문지
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• 제23권12호
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• pp.988-995
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• 2010

In this study the (Alnico, Sm-Co) bonded magnets were fabricated by mixing the Sm-Co added alnico alloy powders with epoxy resin and binder, appropriately. Also, the hybrid ring magnets of (Alnico, Sm-Co)/Sr-ferrite were fabricated by coupling the Sr-ferrite composite layer with an (Alnico, Sm-Co) magnet. The magnetic properties of (Alnico, Sm-Co) ring magnets were varied with the amount of Sm-Co powders. The addition of Sm-Co powders increased a remanent induction($B_r$) and coercive force($_BH_C$), while decreasing a surface flux density and repulsive distance. The surface flux density and repulsive distance for the (Alnico, Sm-Co) ring magnet increased with a magnetizing voltage up to about 160 V and reached an apparent saturation point. Also, the measurements of temperature and moisture characteristics showed that the surface flux densities of N-S poles and repulsive distance decreased a little within 4% after 10 days passed.

• 한국자기학회지
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• 제3권4호
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• pp.284-288
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• 1993

급속냉각기술로 제조된 $Sm_{2}Co_{3}B_{7}$ 화합물의 저온자기특성(77~450 K 범위)과 결정구조를 연구하여 경자성 재료로서의 응용가능성을 조사하였다. P6/mmm 공간격자의 $Sm_{2}Co_{3}B_{7}$은 150~160 K에서 spin-reorientation 현상을 보였으며, 결정자기이방성 자계(Ha)는 300 k 에서 135 kOe, 77 K 에서 725 kOe의 거대 이방화 에너지를 보였다. 그러나 자기능률(magnetic moment)은 25 emu/g에 그쳤다. Rietveld 분석에 의하여 $Sm_{2}Co_{3}B_{7}$의 결정구조를 밝혔으며 B(4h) 원자는 지금까지 보고된 바와는 달리 Sm(2e) 면에 위치한 것이 아니고 Sm(2e) 면에서 $0.792\;{\AA}$ 떨어져 Sm(2e)면과 Co($6i_{1}$) 면 사이에 위치함을 알았다.

• Journal of Magnetics
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• 제8권3호
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• pp.124-127
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• 2003

HDDR (hydrogenation, disproportionation, desorption, recombination) and mechanical milling processes have been applied to the $SmCo_{5}$ alloy in an attempt to produce a highly coercive powder. The $SmCo_{5}$ alloy had very high structural stability under the hydrogen atmosphere and the 1:5 phase was only partially disproportionated under up to 10 kgf/$\textrm{cm}^2$ hydrogen gas. The partially disproportionated material was recombined not into 1:5 phase after the HDDR, but rather into multi-phase mixture consisting of 1:5, 2:17, 2:7 and 1:7 phases. The $SmCo_{5}$ alloy HDDR-treated with hydrogen up to 10 kgf/$\textrm{cm}^2$ had poor coercivity. For a useful HDDR to prepare a high coercivity $SmCo_{5}$ alloy powder, much higher hydrogen pressure well exceeding 10 kgf/$\textrm{cm}^2$ would be required. The $SmCo_{5}$ alloy lump was amorphized by an intensive mechanical milling, and it was crystallised ultra-finely by a subsequent optimum annealing. The optimally annealed material had very high coercivity, and it was found that the mechanical milling followed by an annealing was an effective way of producing highly coercive $SmCo_{5}$ alloy powder.

• 한국자기학회지
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• 제1권1호
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• pp.17-24
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• 1991

$NdFe_2$, $Nd{(Fe_{0.5})}_2$, $SmCo_2$ 및 $Sm{(Fe_{0.5}Co_{0.5})}_2$ 조성의 Laves 화합물을 급속냉각기술에 의하여 제조하였다. 저온자기특성을 조사한 결과 $Nd{(Fe_{0.5}Co_{0.5})}_2$, $SmCo_2$와 $Sm{(Fe_{0.5}Co_{0.5})}_2$ 조성의 Laves 화합물은 강자성의 거동을 보이며 결정구조는 모두 C15의 단일상으로 존재하였으며, $NdFe_2$ 조성의 급냉합금은 일종의 spin reorientation 거동을 보였다. $NdFe_2$ 조성의 급냉합금은 화학조성식 $NdFe_7$의 준안정상과 Nd-rich상으로 구성됨을 알았다. $NdFe_2$ 급냉합금을 열처리 하면 $NdFe_7$은 $Nd_2Fe_{17}$과 Nd-Fe-O상으로 변태하였다. $Sm{(Fe_{0.5}Co_{0.5})}_2$ Laves 화합물의 보자력은 상온에서 4kOe이며 큐리온도는 $400^{\circ}C$로 측정된다. 또한 $Nd{(Fe_{0.5}Co_{0.5})}_2$ Laves 화합물은 상온에서 $2.8\;{\mu}_B/f.u.의$ 자기모멘트를 보유한다.

• 한국자기학회지
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• 제5권5호
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• pp.726-729
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• 1995

We investigated the effects of Sm on the microstructure and magnetic properties of Fe-Co Alloy films prepared by a DC triode sputtering. The magnetostriction was found to be changed with the Sm content from positive to negative values, taking a zero magnetostriction was at about 3 at% Sm. The Sm content dependence of magnetostriction was explained by the formation of Sm enriched amorphous phase surrounding the main bcc (Fe,Co) crystalline phase, which was observed by a high resolution transmission electron microscopy.

• Journal of Magnetics
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• 제6권4호
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• pp.122-125
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• 2001

Phase relationships of the HDDR (hydrogenation, disproportionation, desorption and recombination)-treated Sm$_3$(Fe,M)$_{29}$-type alloy with chemical composition of Sm$_{9}$Fe$_{65}$ $Co_{20}$V$_{6}$ were studied by X-ray diffraction (XRD) and by thermomagnetic analysis (TMA). The alloy was disproportionated into a mixture of $SmH_{x}$ and $\alpha$-Fe at high temperature under hydrogen gas. The disproportionated material was recombined into a mixture of Sm-(Fe,M) (M = Co and/or V) and $\alpha$-Fe phases. The structure of the Sm-(Fe,M) phase was dependent upon the recombination conditions, and a detailed phase diagram showing the phase relationships in the HDDR-treated alloy has been established. The Sm-(Fe,M) phase in material recombined above $900^{\circ}C$ had the $Sm_2Fe_{17}$-type structure, and it exhibited the $SmFe_{7}$-type structure when recombined at temperatures ranging from $700^{\circ}C$ to $850^{\circ}C$. Recombination below $650^{\circ}C$ led to the $SmFe_3$-type structure of the Sm-(Fe,M) phase. Curie temperatures of the Sm-(Fe,M) phases in the recombined material were significantly higher than those of the corresponding stoichiometric phases. It was suggested that the chemical composition of the Sm-(Fe,M) phases may be significantly different from that of the corresponding stoichiometric phases. All the HDDR-treated $Sm_{9}Fe_{65}Co_{20}V_{6}$ materials showed the soft magnetic features regardless of the phase constitution.n.

• 한국동물위생학회지
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• 제23권1호
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• pp.45-59
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• 2000

The present study was conducted to investigate the epidemiological properties of salmonellosis of poultry farms in Kyongbuk province during the relied from November 1998 to November 1999 And antibiotic susceptibility and biochemical characteristics of 120 Salmonella cultures isolated from chicken samples were also investigated. The results obtained through this study were summarized as follows, 1. Among 667,200 chickens of 31 flocks in 17 layer farms and 9 broiler farms, 61,350 chickens of 31 flocks were died with salmonellosis. The death rate of 25 farms varied from 0.1% to 75.0%, and the average death rate was 9.2%. 2. According to etiological agents, fowl typhoid was shown the most predominant outbreak among the salmonellosis during a year, which accounted for 8R.0%(22/25) of the total case 3. The serotypes of 120 Salmonella isolates were identified as 7 strains(5.8%) of S pullorum, 10 strains(8.4%) of S typhimurium and 103 strains(85.8%) of S gallinarum. 4. Most outbreak of fowl typhoid were prevalent on the layer chicken farms(77.1%), and the summer season(45.5%) also appeared the most hazardous season during the year. 5. It seemed that the Hyline breed(70.6%) was the most susceptible among the layer chicken breeds, and followed by Isabrown(23.5%), Tetra(5.9%) in order. 6. In layers, 76.4% of fowl typhoid occurred commonly from 14 to 40 weeks including the early laying peroid, but in broiler farms, all cases was outbreak within first second weeks. 7 All the strains of S pullorum were resistant to lincomycin(Lm), penicillin(Pm), and steptomycin(Sm), but sensitive to amikacin(Ak), ampicillin(Am), cephalothin(Ce), ciprofloxacin (CiP), chloramphenicol(Cm), colistin(Co), enrofloxacin(Enr), furazolidone(Fu), gentamicin(Gm), kanamycin(Km), neomycin(Nm), polymyxin(Po), and teracycline(Tc). All the strains of S typhimurium were resistant to Lm(100%), Pm(100%), Po(90%), and Sm(90%), but were sensitive to Ak, Am, Ce, CiP, Cm, Co, Enr, Fu, Gm, Km, Nm, and Tc. 8. Minimum inhibitory concentration(MIC) of 103 strains of S gallinarum were also evaluated and their patterns were much more variable than others. All the strains of S gallinarum were sensitive to Ak, Am, Ce, Cip, Cm, Enr, Fu, Km, and Nm, but resistant to Lm(100%), and Sm(100%), 99(96.1%) to Co, 83(80.6%) to Pm, and 83(80.6%) to Po, 55(53.4%) to Gm, and 33(32.0%) to Tc. 9. The multiple drug resistance patterns of 120 Salmonella strains were CoLmPmPo Sm pattern(34.2%), CoGmLmPmPoSmTc(20.8%), CoGmLmPmPoSm(13.3%), CoGmLmSm(7.5%), LmPmSm(7.5%), LmPm(6.7%), CoLmSmTc(3.3%),, CoGmLmSmTc(1.7%), GmLmSmTc(1.7%), CoGmLmPoSm(0.1%), LmPmPo(0.1%), CoLm Sm(0.1%), and LmSm(0.1%), in order.