Effect of unoxidized residual Al at the boundary of Co/Al-oxide/Co junction on TMR estimated by LMTO band calculation

Kazuo Shiiki, Naoki Sakaguchi, Hideo Kaiju

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The magneto-resistance effect of Co/Al-oxide/Co tunneling junction is evaluated by a first-principles band calculation. To clarify the effect of unoxidized Al in the Al-oxide layer on the Co layer, we calculated the electronic structures of the junction with a local density approximation using the LMTO-ASA method. Periodic superlattices which consist of layers separated by vacant layers were used for the conventional calculation method. The magneto-resistance ratio, ΔR/R, was estimated by the equation ΔR/R = 2P1P2/(P1 + P2), where P 1 is the polarization of a boundary Co atom on one side of a layer and P2 is the polarization of a Co or Al atom with a vacant layer on the other side. The polarization of Co atoms near the boundary between the Co and Al layers decreases greatly due to the paramagnetic Al, although the Al was polarized by the ferromagnetic Co. These changes of polarization affect the magneto-resistance ratio with calculations indicating that the ratio is reduced by half for two atomic layers of residual Al.

Original languageEnglish
Pages (from-to)64-66
Number of pages3
JournalThin Solid Films
Volume505
Issue number1-2
DOIs
Publication statusPublished - 2006 May 18

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Oxides
Magnetoresistance
Polarization
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Atoms
Local density approximation
Superlattices
polarization
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Keywords

  • Co-Al boundary
  • LMTO band calculation
  • Spin tunneling junction

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry

Cite this

Effect of unoxidized residual Al at the boundary of Co/Al-oxide/Co junction on TMR estimated by LMTO band calculation. / Shiiki, Kazuo; Sakaguchi, Naoki; Kaiju, Hideo.

In: Thin Solid Films, Vol. 505, No. 1-2, 18.05.2006, p. 64-66.

Research output: Contribution to journalArticle

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N2 - The magneto-resistance effect of Co/Al-oxide/Co tunneling junction is evaluated by a first-principles band calculation. To clarify the effect of unoxidized Al in the Al-oxide layer on the Co layer, we calculated the electronic structures of the junction with a local density approximation using the LMTO-ASA method. Periodic superlattices which consist of layers separated by vacant layers were used for the conventional calculation method. The magneto-resistance ratio, ΔR/R, was estimated by the equation ΔR/R = 2P1P2/(P1 + P2), where P 1 is the polarization of a boundary Co atom on one side of a layer and P2 is the polarization of a Co or Al atom with a vacant layer on the other side. The polarization of Co atoms near the boundary between the Co and Al layers decreases greatly due to the paramagnetic Al, although the Al was polarized by the ferromagnetic Co. These changes of polarization affect the magneto-resistance ratio with calculations indicating that the ratio is reduced by half for two atomic layers of residual Al.

AB - The magneto-resistance effect of Co/Al-oxide/Co tunneling junction is evaluated by a first-principles band calculation. To clarify the effect of unoxidized Al in the Al-oxide layer on the Co layer, we calculated the electronic structures of the junction with a local density approximation using the LMTO-ASA method. Periodic superlattices which consist of layers separated by vacant layers were used for the conventional calculation method. The magneto-resistance ratio, ΔR/R, was estimated by the equation ΔR/R = 2P1P2/(P1 + P2), where P 1 is the polarization of a boundary Co atom on one side of a layer and P2 is the polarization of a Co or Al atom with a vacant layer on the other side. The polarization of Co atoms near the boundary between the Co and Al layers decreases greatly due to the paramagnetic Al, although the Al was polarized by the ferromagnetic Co. These changes of polarization affect the magneto-resistance ratio with calculations indicating that the ratio is reduced by half for two atomic layers of residual Al.

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