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Mean Field Analysis of Exchange Coupling in Amorphous REFe₂-B (RE = Dy, Sm) Alloy Ribbons
이정미(J. M. Lee),정재국(J. K. Jung),임상호(S. H. Lim) 한국자기학회 2001 韓國磁氣學會誌 Vol.11 No.3
Experimental magnetization-temperature curves for melt-spun ribbons of amorphous alloys (Dy_(0.33)Fe_(0.67))_(1-x)Bx (x=O, 0.05, 0.1, and 0.15) and (Sm_(0.33)Fe_(0.67))_(1-x)Bx (x=O, 0.01, 0.02, and 0.03) (in atomic fraction) are fitted with theoretical equations based on the mean field theory in order to calculate exchange couplings between constituent elements as a function of the B content. In the case of the DyFe₂-B system, the sign of the exchange coupling between Dy and Fe is negative, indicating that the magnetization direction of Dy is anti parallel to that of Fe. The sign of the other two couplings are positive indicating a parallel alignment. The exchange coupling between Fe ions are greatest, while that between Dy ions is negligible. In the case of the SmFe₂-B alloys, the sign of all the couplings are positive, indicating ferromagnetic coupling between the spins. The exchange couplings between Fe ions, and Fe and Sm are comparable to each other, but they are much greater than that between Sm ions. The high exchange coupling between Fe and Sm, which is considered to occur indirectly, is rather unexpected, but it is considered to be unique characteristics of amorphous Sm-Fe alloys. In both alloy systems, the exchange coupling between Fe ions increases with increasing B content, and this may be explained by the increase of the Fe-Fe separation with increasing B content. The exchange coupling between Fe and RE also increases with increasing B content. As the B content increases, the magnetization decreases over the whole temperature range, and the Curie temperature also decreases.
박미경 ( M. K. Park ),이정미 ( J. M. Lee ),최지연 ( J. Y. Choi ),이경화 ( K. H. Lee ),이배환 ( B. H. Lee ),손진훈 ( J. H. Sohn ) 한국감성과학회 2000 추계학술대회 Vol.2000 No.-
본 연구는 향의 감성 구조를 밝히고, 향 선호도를 예측하는 감성요인을 규명하며, 향에 대한 자율 신경계 반응을 밝히는 것이 목적이다. 향에 대한 주관적인 감성을 측정하기 위하여, 25개의 감성 형용사로 구성된 향 감성 측정 척도를 개발하였다. 개발된 이 척도를 이용하여 lavender, lemon, rose, jasmin, peppermint의 다섯 가지 향에 대해 대학생 50명을 대상으로 향 감성 평가를 실시하였다. 향에 대한 감성 구조는 심미성, 강도, 자연성, 여성성-남성성, 개성, 중량감의 여섯 요인으로 구성되었다. 향에 대한 자율 신경계 반응 측정은 대학생 20명을 대상으로 lavender, lemon, rose, jasmin, peppermint 향에 대해 실시하였다. 향에 대한 자율 신경계 반응 측정 결과, PPG 반응은 남녀 모두 lavender, lemon 향에서 유의미하게 감소하였다. 남자의 경우, PPG 반응은 rose, peppermint 향에서도 유의미하게 감소하였고, SKT 반응은 lavender, jasmin 항에 대해서 유의미하게 증가하였다.
(NiFe / CoFe) / Cu / CoFe Spin - Valve 박막의 자기저항 특성
오미영(M. Y. Oh),이선영(S. Y. Lee),이정미(J. M. Lee),김미양(M. Y. Kim),이장로(J. R. Rhee) 한국자기학회 1997 韓國磁氣學會誌 Vol.7 No.5
The MR ratios and the exchange biasing field and interlayer coupling field were investigated in Ni_(81)Fe_(19)/Co_(90)Fe_(10)/Cu_(90)Fe_(10) spin-valve sandwiches grown on anti ferromagnetic NiO films as a function of the NiO thickness, the thickness of Cu and pinning layer Co_(90)Fe_(10). The spin-valve sandwiches were deposited on the Corning glass 7059 by means of the 3-gun dc and 1-gun rf magnetron sputtering at a 5 mtorr partial Ar pressure and room temperature. The deposition field was 50 Oe. The MR curve was measured by the four-terminal method with applied magnetic field up to 500 Oe perpendicular to the direction of a current in the plane. The coercivity of magnetic soft bilayer [NiFe/CoFe] (90 Å) decreased dramatically to less than 10 Oe when the NiFe/CoFe bilayer used an NiFe bilayer thicker than 20 Å. SO NiFe layer improved the softmagnetic properties in the NiFe/CoFe bilayer. The GMR ratio and the magnetic field sensitivity of the spin-valve film Ni_(91)Fe_(19)(40 Å)/Co_(90)Fe_(10)(50 Å)/Cu(30 Å)/Co_(90)Fe_(10)(35 Å)/NiO(800 Å) was 6.3 % and about 0.5(%/Oe), respectively. The MR ratio had 5.3 % below an annealing temperature of 200℃ which slowly decreased to 3 % above 300℃. The large blocking temperature of the spin-valve film was taken (as being) due to the good stability of the NiO films. Thus, the spin-valve films with a free NiFe/CoFe layer clearly had a high large GMR output and showed a effective magnetic field sensitivity for a suitable spinvalve head material.
[FeNi / Cu / CoFe(Co) / Cu]N Spin - Valve 다층박막의 자기저항 특성
김미양(M. Y. Kim),이정미(J. M. Lee),최규리(K. L. Choi),오미영(M. Y. Oh),이장로(J. R. Rhee) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.1
Buffer/[NiFe/Cu/CoFe(Co)/Cu]_N spin-valve multilayers prepared by dc magnetron sputtering on a coming glass substrate using NiFe and CoFe(Co) possess different coercivities. Dependence of magnetoresistance on the type and thickness of buffer layer, thickness of Cu, NiFe, stacking number of multilayer, substrate temperature and annealing temperature in the form [NiFe/Cu/CoFe(Co)/Cu]_N spin-valve multilayers were investigated. To evaluate effect of magnetoresistance for this samples, X-ray diffraction analysis, vibrating sample magnetometer analysis, and magnetoresistance measurement (4-probe method) were performed. The maximum magnetoresistance ratio and coercivity were 7.5 % and 140 Oe, respectively for Cr-50Å/[NiFe-20Å/Cu-50Å/Co-20Å/Cu-50Å]_(10) at substrate temperature of 90 ℃. Magnetoresistance slope maintained 0.25% / Oe until 150 ℃ of annealing temperature, and then decreased to 0.03% / Oe at 200 ℃. It was confirmed that the main factor of thermal stability was deteriorating of soft magnetic properties in the NiFe layer.