Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Junction Size Dependence of Magnetic and Magnetotransport Properties in MTJs

자기터널절합에서 자기 및 자기저항의 접합크기 의존성

  • Sankaranarayanan, V.K. (Department of Materials Science and Engineering Chungnam National University) ;
  • Hu, Yong-kang (Department of Materials Science and Engineering Chungnam National University) ;
  • Kim, Cheol-Gi (Department of Materials Science and Engineering Chungnam National University) ;
  • Kim, Chong-Oh (Department of Materials Science and Engineering Chungnam National University) ;
  • Lee, Hee-bok (Department of Pysics Education, Kongju National University)
  • 상카라나라얀 (공주대학교 사범대학 물리학과) ;
  • 호영강 (충남대학교 공과대학 재료공학과) ;
  • 김철기 (충남대학교 공과대학 재료공학과) ;
  • 김종오 (충남대학교 공과대학 재료공학과) ;
  • 이의복 (공주대학교 사범대학 물리학과)
  • Published : 2003.06.01
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Abstract

Magneto-optic Kerr Effect(MOKE), AFM and magnetoresistance measurements have been carried out on as-deposited and annealed Magnetic Tunnel Junctions(MTJs) with junction sizes 180, 250, 320 and 380 $\mu\textrm{m}$ in order to investigate the correlation among interlayer exchange coupling, surface roughness and junction size. Relatively irregular variations of coercivity $H_{c}$ (∼17.5 Oe) and interlayer exchange coupling $H_{E}$ (∼17.5 Oe) are observed over the junction in as-deposited sample prepared by DC magnetron sputtering. After annealing at $200^{\circ}C$, $H_{c}$ decreases to 15 Oe, while $H_{ E}$ increases to 20 Oe with smooth local variation. $H_{E}$ shows very good correlation with surface roughness across the junction in agreement with Neel's orange peel coupling. The increasing slope per $\mu\textrm{m}$ of normalized $H_{c}$ and $H_{E}$ are same near junction edge along free-layer direction irrespective of junction size, giving relatively uniform $H_{c}$ and $H_{ E}$ for wider junction size. Thickness profiles of the junctions measured with $\alpha$-step show increasingly flat top surface for larger junctions, indicating better uniformity for large. junctions in agreement with the normalized$ H_{c}$ and H$/_{E}$ curves. TMR ratios also increase with increasing junction size, indicating improvement for larger uniform junctions.

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References

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