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Sputtering 성막속도가 박막의 특성에 미치는 영향
이기암(Ky Am Lee) 한국진공학회(ASCT) 1993 Applied Science and Convergence Technology Vol.2 No.2
본 연구에서는 DC magnetron sputtering 장비를 이용하여, GdFe, Co, CoCr 박막을 제작함에 있어서 sputtering 조건에 관계되는 Ar 압력, 투입전력, 기판의 종류 등의 요소가 박막의 특성, 특히 보자력과 미세구조에 미치는 영향을 관찰하였다. GdFe의 경우 성막속도가 증가함에 따라 Gd의 atomic%가 줄어드는 것을 알 수 있었으며, Ar 압력이 증가함에 따라 성막속도는 감소하였고, 투입전력이 증가함에 따라 성막속도는 거의 선형적으로 증가함을 알 수 있었다. 또한 투입전력이 증가함에 따라 박막의 보자력도 증가함을 알 수 있었다. Co 박막에 대해서는 투입전력과 Ar 압력에 관한 성막속도와 미세구조에 관하여 관찰하였다. 이로써 투입전력이 증가하면 성막속도가 증가하며 결정립의 크기가 감소함을 알 수 있었고, Ar 압력이 증가하면 성막속도가 감소함을 알 수 있었다. CoCr의 박막에서는 substrate 종류에 따라 보자력 및 미세구조에 미치는 영향에 대해 연구를 행하였으며, substrate의 종류가 미세구조와 보자력에 상당한 영향을 준다는 것을 알 수 있었다. In this study, we have investigated the influence of sputtering conditions (Ar pressure, input powers, substrates) on coercivity and microstructures of GdFe, Co, CoCr thin films produced by the method of DC magnetron sputtering. In GdFe films, we have observed that the Gd atomic ratio was decreased with the deposition rate, and the deposition rate decreased with the pressure of Ar gas and the increased linearly with input power. It was also observed that the coercivity of thin films was increased with input power. In Co films, we have investigated the deposition was increased and the Co thin film became finer structure with the increase in the input power, was increased and the Co thin film became finear structure with the increase in the input power, and the deposition rate was decreased with the pressure of Ar gas. In CoCr films, we have investigated the effects of substrates on the coercivity (H_c) and the microstructure. We have found that the substrates plays a crucial role in the microstructure and the coercivity (H_c).
수직자기이방성을 갖는 [Pd/Co] Spin Valve 구조에서 자기저항효과
최진협(Jin-Hyup Choi),이기암(Ky-Am Lee) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.3
We have investigated the magnetoresistance (MR) effect of the spin valve structures composed of perpendicularly magnetized Pd/Co multilayers, with changing the space layer (Pd or Cu) thickness, the stacking number of the Pd/Co multilayers, and the Co insertion-layer thickness. The Cu space layer showed larger MR ratio than the Pd space layer. The Co insertion-layer between Cu layer and pinned layer enhanced the MR ratio about three times. The maximum MR ratio of 7.4 % was established in the sample with the Co insertion-layer thickness of 0.62 and 1.01 ㎚.
기저층 및 열처리 효과가 Co / Cu 다층박막의 자기저항에 미치는 영향
김미양(Mee-Yang Kim),최규리(Kyu-Lee Choi),최수정(Soo-Jung Choi),송은영(Eun-Young Shong),이장로(Jang-Roh Rhee),황도근(Do-Guwn Hwang),이상석(Sang-Suk Lee),박창만(Chang-Man Park),이기암(Ky-Am Lee) 한국자기학회 1997 韓國磁氣學會誌 Vol.7 No.2
Dependence of magnetoresistance on the thickness of Cu, type and thickness of buffer layer, and the stacking number of multilayer in the form buffer /[Co(17Å)/Cu(tÅ)]_(20) were investigated. To evaluate effect of annealing on this samples, X-ray diffraction analysis, vibrating sample magnetometer analysis, and magnetoresistance measurement(4-probe method) were performed. The magnetoresistance ratio exhibits a maximum of 21% for the multilayer with Cu thickness of 24Å and Fe buffer layer thickness of 50Å. Deposition of film under low base pressure induces in increase magnetoresistance ratio by preventing oxidation. The multilayer annealed below 300℃ temperature allowed larger textured grain without loss in the periodicity. Magnetoresistance ratios of the multilayer with Cu thickness of 24Å and 36Å were increased due to the increase in the antiferromagnetically coupled fraction after annealing.
[Pd/Co] 다층박막을 이용한 수직스핀밸브 구조에서 비자성층에 인접한 강자성 물질과 그 두께에 따른 자유층의 보자력 변화
허장(Jang Heo),최형록(Hyongrok Choi),이기암(Ky Am Lee) 한국자기학회 2010 韓國磁氣學會誌 Vol.20 No.3
We study the giant magneto-resistance (GMR), coercivity and their dependence on the ferromagnetic layers adjacent to the nonmagnetic layer in a spin-valve structure, [Pd/ferromagnetic] multilayers with perpendicular anisotropy. We fabricated a basic spinvalve structure of [Pd/Co]₂/ferro-magnetic layer/nonmagnet/ferro-magnetic layer/[Pd/Co]₂/FeMn and investigated the dependence of its GMR and magnetic properties such ad coercivity on the ferromagnetic material to reduce the coercivity of the free layer. We try to reduce the freelayer coercivity by controlled the anisotropy, we insert the material NiFe, Co?Fe₂, Co?Fe₁ to ferromagnetic layers adjacent to the Cu layer. Then, we have been able to reduce the coercivity as low as 100 Oe, and also achieved 6.7 % of magnetoresistance ratio when the ferromagnetic layer thickness was 0,7 ㎚.
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.
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.