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[Pd / Co]5 / FeMn 막에서의 바닥층과 삽입층에 의한 교환바이어스수직자기이방성
주호완(Ho Wan Joo),안진희(Jin Hee An),이미선(Mi Sun Lee),김보근(Bo Keun Kim),최상대(Sang Dea Choi),이기암(Kee Am Lee) 한국자기학회 2004 韓國磁氣學會誌 Vol.14 No.5
Magnetic properties by exchange biased perpendicular magnetic anisotropy in [Pd(0.8 ㎚)/Co(0.8 ㎚)]_5/FeMn(15 ㎚) multilayers deposited by dc magnetron sputtering system are investigated. As inserted Pd layer of interface between [Pd/Co] multilayer and FeMn film, the Hex of perpendicular anisotropy was improved from 127 Oe to 145 Oe. But result of an experiment by thermal stability, the Hex of the case that an inserted layer was inserted in decreased from low 200℃ in about 50℃ more if not inserted. If Ta was a buffer layer, the experiment results along material of buffer layer, the Hex obtained the largest 127 Oe. And if Pd was a buffer layer, Hex obtained the largest 169 Oe. Also, the Hc in buffer layer of Ta and Pd obtained the largest 203 Oe and 453 Oe, respectively.
Ta / NiFe / Cu / Co Pseudo 스핀밸브 구조의 자기저항 효과
주호완(Ho-wan Joo),최진협(Jin-hyup Choi),최상대(Sang-Dae Choi),이기암(Ky-Am Lee) 한국자기학회 2004 韓國磁氣學會誌 Vol.14 No.1
The dependence of sensitivity, MR ratio, coercivity (Hc) and switching fields as a function of thickness of each magnetic layers (Co, NiFe and Cu) were investigated in pseudo spin valves with a structure of Ta/NiFe/Cu/Co. As measured results dependence of the thickness of each magnetic layer, we obtained MR ratio of 7.26% for Ta(4 ㎚)/NiFe(7.5 ㎚)/Cu(3 ㎚)/Co(5 ㎚) pseudo spin valves. Also, we could control properties of magnetoresistance for independent magnetization courses of each magnetic layer. Especially, we found that we could control coercivity as constant MR ratio dependence of Co thickness.
[Pd / Co]N / FeMn 다층막에서의 교환바이어스 수직자기이방성과 열적안정성
주호완(Ho-Wan Joo),안진희(Jin-Hee An),김보근(Bo-Keun Kim),김선욱(Sun-Wook Kim),이기암(Kee-Am Lee),황도근(Do-Geun Hwang),이상석(Sang-Suk Lee) 한국자기학회 2004 韓國磁氣學會誌 Vol.14 No.4
Magnetic properties and thermal stability by exchange biased perpendicular magnetic anisotropy in [Pd/Co]_N/FeMn multilayer deposited by dc magnetron sputtering system are investigated. We measured the perpendicular magnetization curves of [Pd(0.8 ㎚)/Co(0.8 ㎚)]_5/FeMn multilayer as function of FeMn thickness and annealing temperature. As FeMn thickness increases from 0 to 21 ㎚, the perpendicular exchange bias(Hex) obtained 127 Oe at FeMn thickness 15 ㎚. As the annealing temperature increases to 240℃, the Hex increased from 115 Oe to 190 Oe and disappeared exchange biased perpendicular magnetic anisotropy effect at 330℃.
자연산화된 자유층을 갖는 NiO 스핀밸브 박막의 자기저항특성
김종기(Jong-Kee Kim),주호완(Ho-Wan Joo),이기암(Ky-Am Lee),황도근(Do-Guwn Hwang),이상석(Sang-Suk Lee),박달호(Dal-Ho Park) 한국자기학회 2001 韓國磁氣學會誌 Vol.11 No.3
The effect of specular electron scattering on natural oxidation of free layer in NiO spin valves have been investigated. The magnetoresistance (MR) ratio and the exchange biasing field (Hex) of NiO(600 Å)/Ni_(81)Fe_(19)(50 Å)/Co(7 Å)/Cu(20 Å)/ Co(7 Å)/Ni_(81)Fe_(19)(70 Å) spin valves were increased from 4.9 % to 7.3 %, and 110 Oe to 170 Oe after natural oxidation in the atmosphere for 80 days, respectively. The sheet resistivity p decreased from 28 μΩm to 17 μΩm, but Δp did not almost change after the oxidation. The spin valves enhanced by the specular electron scattering in the naturally oxidized Co/NiFe/NiFeOx, free layer were confirmed from the depth profiles using Auger electron spectroscopy.
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.
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.
α-Fe₂O₃ / NiFe / Cu / NiFe 스핀밸브 박막에서의 자기저항 특성에 대한 연구
김종기(Jong-Kee Kim),주호완(Ho-Wan Joo),이기암(Ky-Am Lee),황도근(Do-Guwn Hwang),이상석(Sang-Suk Lee) 한국자기학회 2000 韓國磁氣學會誌 Vol.10 No.1
We investigated the magnetoresistance effect and the exchange coupling of antiferromagnetic Fe₂O₃ spin-valve film. The X-ray diffractions of the spin-valve films having a different thickness of a α-Fe₂O₃ were measured. The exchange coupling field (Hex) between Fe₂O₃ and pinned NiFe layer was increased from 13.5 Oe to 84.5 Oe, as the thickness of Fe₂O₃ increased from 400 Å to 800 Å. The surface roughness of α-Fe₂O₃ spin-valves increased with the increase of α-Fe₂O₃ thickness. Therefore, the increase of Hex will be due to the increase of the interface roughness. The MR ratios as a function of Fe₂O₃ thickness was not changed. And Hex increased by the increment of magnetostatic coupling between Fe₂O₃ and NiFe (pinned-layer) due to the increment of interface roughness. Hex depends on the surface roughness, but the magnetoresistance ratio doesn't.
이상석,박상현,소광섭,주호완,김기왕,황도근,Lee, Sang-Suk,Park, Sang-Hyun,Soh, Kwang-Sup,Joo, Ho-Wan,Kim, Gi-Wang,Hwang, D.G. 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.4
셀(cell) 단위의 생체분자의 자성특성 검출을 위한 거대자기저항-스핀밸브(giant magnetoresistance-spin valves; GMR-SV) 바이오센서로서 미세 패턴된 모양에 따라 길이 방향과 폭 방향 용이축에 의존하는 자기저항 특성을 연구하였다. 바이오센서(biosensor)로서 사용할 스핀밸브 다층구조는 glass/NiO/NiFe/CoFe/Cu/CoFe/NiFe 이었다. 자성 다층박막의 일축이방성을 만들기 위해 증착시와 소자 패턴닝 후 진공 열처리를 $200^{\circ}C$에서 300 Oe 정도 외부자기장을 인가하였다. 형상자기이방성 효과를 고려하여 광 리소그래피 과정으로 얻은 미세 활성영역 패턴 사이즈는 $2{\times}5{\mu}m^2$로 정하였다. 2단자법으로 길이방향의 센싱전류와 폭 방향의 고정층의 용이축 방향 각도에 의존하는 자장민감도의 변화는 바이오센서 소자로서 활용에 중요한 요인임을 확인하였다. In order to detect of the magnetic property in the cell unit, we studied the GMR-SV (giant magnetoresistance-spin valves) biosensor, which was depended on the micro patterned features according to two easy directions of longitudinal and transversal axes. Here, the multi layer structure was glass/NiO/NiFe/CoFe/Cu/CoFe/NiFe. The uniaxial anisotropy direction was applied to the patterned biosensor during the deposition and vacuum post-annealing at $200^{\circ}C$ under the magnitude of 300 Oe, respectively. Considering the magnetic shape anisotropy effect, the size of micro patterned biosensor was a $2{\times}5{\mu}m^2$ after the photo lithography process. By our experimental results, we confirmed that the best condition of GMR-SV biosensor should be the same direction of the axis sensing current and the easy axis of pinned NiO/NiFe/CoFe triple layer oriented to the width direction of device, and the direction of the easy axis of free CoFe/NiFe bilayer was according to the longitudinal direction of device.