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산화층 삽입에 따른 NiO / Co / Cu / Co 스핀밸브 박막의 열처리에 의한 자기적 특성
최상대(Sang-Dae Choi),주호완(Ho-wan Joo),최진협(Jin-hyup Choi),이기암(Ky-Am Lee) 한국자기학회 2004 韓國磁氣學會誌 Vol.14 No.1
Magnetic properties are investigated for spin valves of Si/SiO₂/Ta(3 ㎚)/NiO(60 ㎚)/Co(2.5 ㎚)/Cu(1.95 ㎚)/ Co(4.5 ㎚)/NOL(tnm ; Nano Oxide layer)/Ta(3 ㎚) with annealing. The annealing effect of spin valves with NOL are shown larger MR ratios from 10 % to 12 %. However lower enhancement of MR ratios. The spin-valves with NOL also showed almost constant △R and smaller R. Enhanced MR ratios of spin valves with NOL after annealing result mainly from small values of R with constant △R which due to specular diffusive electron scattering at NOL(NiO)/metal interfaces.
Laser 열처리를 이용한 FeMn / NiFe 박막의 자화 반전
최상대(S. D. Choi),진대현(D. H. Jin),김선욱(S. W. Kim),김영식(Y. S. Kim),이기암(K. A. Lee),이상석(S. S. Lee),황도근(D. G. Hwang) 한국자기학회 2004 韓國磁氣學會誌 Vol.14 No.6
We have studied local magnetization reversal and magnetic properties induced by Laser annealing method in the strip-patterned Ta/NiFe/FeMn/Ta and Ta/NiFe/FeMn/NiFe/Ta multilayers fabricated by ion-beam deposition. The films were exposed to the emission of the DPSS (Diode Pumped Solid State, Nd:YAG) laser under 600 G. The laser beam intensity increased up to 440 ㎽. When the laser illuminated the patterned film with the power of above 200 ㎽, the intensity of MR peak located in +87 Oe shrunk. A new MR peak was generated at -63 Oe. When the laser power is 400 ㎽, the location of positive MR peak(Hex) was changed slightly from +87 Oe to +76 Oe, and the MR ratio was decreased from 0.9% to 0.1 %. On the other hand, the new (negative) MR peak shifted from -63 Oe to -80 Oe, with the MR ratio increased up to 0.3%. As the illuminated area expanded, the intensity of opposite MR peak increased and it of negative MR peak decreased. This proved that the local reversal of exchange biasing should be realized by laser annealing.
최상대(S. D. Choi),김미선(M. S. Kim),안명천(M. C. Ahn),최영근(Y. G. Choi),김기왕(G. W. Kim),박달호(D. H. Park),황도근(D. G. Hwang),이상석(S. S. Lee) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.4
The electric signals for the voltage as a function of distance between Hall devices and permanent magnets over the radial artery were investigated. The electric signals, that means signals of arterial pulse wave, were differentiated by the hardware of circuits and then were changed to differential signals as magnetic field. The 3-D images simulated by the software as function of the intensity of differential signals were achieved. It shows that these system can apply to pulse diagnostic apparatus of portable type medical instrument.
NiO 스핀밸브 박막의 Specular Effect에 의한 자기저항비의 향상에 대한 연구
최상대(Sang-Dae Choi),주호완(Ho-wan Joo),이기암(Ky-Am Lee) 한국자기학회 2002 韓國磁氣學會誌 Vol.12 No.6
Magnetic properties are investigated for top- and bottom-type spin valves of NiO(60 ㎚)/Co(2.5 ㎚)/Cu(1.95 ㎚)/ Co(4.5 ㎚)/ NOL (t ㎚; Nano Oxide layer). The MR ratios of the bottom-type spin valves with NOL are larger than those of the top-type spin valves. However, the enhancement of the former is lower than the latter. Both of spin-valves also showed almost constant Δp and smaller p. Enhanced MR ratios of spin valves with NOL result mainly from small values of with constant Δp which due to specular diffusive electron scattering at NOL (NiO)/metal interfaces.
안명천,최상대,주호완,김기왕,황도근,이장로,이상석,Ahn, M.C.,Choi, S.D.,Joo, H.W.,Kim, G.W.,Hwang, D.G.,Rhee, J.R.,Lee, S.S. 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.4
어레이(away) 자성센서 개발을 위해 고진공 스퍼터링 증착장비를 이용하여 스펙큘러형(specular type) Glass/Ta(5)/NiFe(7)/IrMn(10)/NiFe(5)/$O_2$/CoFe(5)/Cu(2.6)/CoFe(5)/$O_2$/NiFe(7)/Ta(5)(nm) 거대자기저항-스핀밸브(giant magnetoresistive-spin valves; CMR-SV)박막을 제작하였다. 다층박막 시료를 $20{\times}80{\mu}m^2$의 미세 활성영역을 가진 15개 어레이를 $8{\times}8mm^2$ 영역 내에 최적화한 제작 조건으로 광 리소그래피 패터닝 하였다. Cu를 증착하여 만든 2단자 전극법으로 측정한 자성특성은 15개 모든 소자들이 균일한 자기저항특성을 나타내었고, 5 Oe 근방에서 가장 민감한 자기저항비 자장민감도와 출력전압들은 각각 0.5%/Oe, ${\triangle}$V: 3.9 mV이었다. 형상자기이방성이 적용된 상부 자유층 $CoFe/O_2/NiFe$층은 하부 고정 자성층 $IrMn/NiFe/O_2/CoFe$층 자화 용이축과 직교하였다. 측정시 인가전류 값을 각각 1 mA에서 10 mA까지 인가하였을 때 출력 작동 전압 값은 균일하게 증가하였으며, 자장감응도도 거의 일정하여 미세 외부자장에 민감한 나노자성소자로서 좋은 특성을 띠었다. To develop array magnetic sensors, specular-type giant magnetoresistive- spin valve (GMR-SV) film of Glass/Ta(5)MiFe(7)/IrMn(10)NiFe(5)/$O_2$/CoFe(5)/Cu(2.6)/CoFe(5)/$O_2$/NiFe(7)/Ta(5)(nm) was deposited by using a high-vacuum sputtering system. One of 15 way sensors in the area of $8{\times}8mm^2$ was Patterned a size of $20{\times}80{\mu}m^2$ in multilayer sample by Photo-lithography. All of 15 sensors with Cu electrodes were measured a uniform magnetic properties by 2-probe method. The highest magnetic sensitivity of MR and output voltage measured nearby an external magnetic field of 5 Oe were MS = 0.5%/Oe and ${\triangle}$V= 3.0 mV, respectively. An easy-axis of top-free layers of $CoFe/O_2/NiFe$ with shape anisotropy was perpendicular to one of bottom-pinned layers $IrMn/NiFe/O_2/CoFe$. When the sensing current increased from 1 mA to 10 mA, the output working voltage uniformly increased and the magnetic sensitivity was almost stable to use the nano-magnetic devices with good sensitive properties.