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CoFeSiB/Ru/CoFeSiB 자유층을 갖는 자기터널 접합의 스위칭 자기장
이선영,이서원,이장로,Lee, S.Y.,Lee, S.W.,Rhee, J.R. 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.3
Magnetic tunnel junctions (MTJs), which consisted of amorphous CoFeSiB layers, were investigated. The CoFeSiB layers were used to substitute for the traditionally used CoFe and/or NiFe layers with an emphasis given on understanding the effect of the amorphous free layer on the switching characteristics of the MTJs. CoFeSiB has a lower saturation magnetization ($M_s\;:\;560\;emu/cm^3$) and a higher anisotropy constant ($K_u\;:\;2800\;erg/cm^3$) than CoFe and NiFe, respectively. An exchange coupling energy ($J_{ex}$) of $-0.003\;erg/cm^2$ was observed by inserting a 1.0 nm Ru layer in between CoFeSiB layers. In the Si/$SiO_2$/Ta 45/Ru 9.5/IrMn 10/CoFe 7/$AlO_x$/CoFeSiB 7 or CoFeSiB (t)/Ru 1.0/CoFeSiB (7-t)/Ru 60 (in nm) MTJs structure, it was found that the size dependence of the switching field originated in the lower $J_{ex}$ using the experimental and simulation results. The CoFeSiB synthetic antiferromagnet structures were proved to be beneficial for the switching characteristics such as reducing the coercivity ($H_c$) and increasing the sensitivity in micrometer size, even in submicrometer sized elements. 비정질 $Co_{70.5}Fe_{4.5}Si_{15}B_{10}$층을 갖는 자기터널접합(magnetic tunneling junctions; MTJ)를 연구하였다. 비정질 자유층이 MTJ의 스위칭 특성에 미치는 영향을 중점적으로 이해하기 위하여 기존의 사용된 CoFe 그리고 NiFe층들을 대신하여 비정질 강자성체 CoFeSiB을 사용하였다. CoFeSiB은 CoFe과 NiFe보다 각각 낮은 포화자기장($M_s:\;560\;emu/cm^3$)과 높은 자기이방성 상수($K_u:\;0.2800\;erg/cm^3$)를 갖는다. CoFeSiB층들의 사이에 1.0 nm Ru층 삽입시 $-0.003\;erg/cm^3$ 교환결합에너지($J_{ex}$)를 나타내었다. $Si-SiO_2-Ta$ 45/Ru 9.5/IrMn 10/CoFe 7/$AlO_x$/CoFeSiB 7 또는 CoFeSiB (t)/Ru 1.0/CoFeSiB (7-t)/Ru 60(in nm) MTJ 구조의 터널접합에 대하여 실험 및 시뮬레이션 결과를 통하여 낮은 $J_{ex}$에 기인하는 스위칭 자기장(switching field; $H_{sw}$)의 시료 크기 의존성이 나타나는 것을 알 수 있었다. CoFeSiB 합성형 반강자성 구조는 micrometer뿐만 아니라 submicrometer 시료 크기영역에서도 보자력($H_c$)의 감소와 민감도를 증가 시킴으로써 자기 스위칭 특성에 유리한 것으로 확인 되었다.
Ni25Mn75 - Spin Valve 박막 자유층의 열처리 순환수에 따른 자기저항 특성
이낭이(N. I. Lee),이주현(J. H. Yi),이가영(G. Y. Lee),김미양(M. Y. Kim),이장로(J. R. Rhee),이상석(S. S. Lee),황도근(D. G. Hwang) 한국자기학회 2000 韓國磁氣學會誌 Vol.10 No.2
Annealing cycle number and nonmagnetic layer thickness dependences of interlayer coupling field (Hinf) and coercivity (Hcf) of free magnetic layer on NiMn alloy-spin valve films (SVF) were investigated. The SVF is Glass (7059)/Ni_(81)Fe_(19)(70Å)/Co(10 Å)/Cu(t Å)/Co(15 Å)/Ni_(81)Fe_(19)(35 Å)/Ni_(25)Mn_(75)(250 Å)/Ta(50 Å) films, it were fabricated using the dc sputtering method at different pinning layer thickness and nonmagnetic spacer thickness (Cu thickness; 30 Å, 35 Å, 40 Å) of NiMn alloy with 25 at.%. Ni In case that Cu thickness of SVF is 35 Å and peak exchange coupling field (Hex) was 620 Oe, while coercivity Hc=280 Oe and MR ratio showed 2.5%. As for Hinf and Hcf, every SVF increased up to the stabilized values with the increase of annealing cycle number 15, which were Hinf of 120 Oe and Hcf of 75 Oe. The increase of Hcf with the annealing cycle number seems to be caused by the effective reduction of Cu layer thickness due to the increase of interfacial mixing of Cu layer and Co layer. In addition, the Hinf and Hcf dependences of free NiFe layer by the interfacial mixing effect were appeared the different aspects when Cu layer becomes more thinner and thicker than Cu layer thickness of 35 Å, respectively.