Computer simulation of magnetization flop in magnetic tunnel junctions exchange-biased by synthetic antiferromagnets

Y. R. Uhm, Sang Ho Lim

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Computer simulation in a single domain multilayer model is used to investigate magnetization flop in magnetic tunnel junctions, exchange-biased by pinned synthetic antiferromagnets with the multilayer structure NiFe/AlOx/Co/Ru/Co/FeMn. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy and hence increased coercivity of the Co layers in the synthetic antiferromagnet. However, when the synthetic antiferromagnet is not or weakly pinned, the magnetization directions of the two layers sandwiching AlOx, which mainly determine the magnetoresistance, are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal MR change from the high MR state to zero, irrespective of the direction of the free layer switching. This emphasizes an importance of a strong pinning of the synthetic antiferromagnet at small cell dimensions. The threshold field for magnetization flop is found to increase linearly with increasing antiferromagnetic exchange coupling between the two Co layers in the synthetic antiferromagnet. The restoring force from magnetization flop to the normal synthetic antiferromagnetic structure is roughly proportional to the resistance to magnetization flop. Irrespective of the magnetic parameters and cell sizes, the state of magnetization flop does not exist near Ha = 0, indicating that magnetization flop is driven by the Zeeman energy.

Original languageEnglish
Pages (from-to)206-214
Number of pages9
JournalJournal of Magnetism and Magnetic Materials
Volume237
Issue number2
DOIs
Publication statusPublished - 2001 Dec 1
Externally publishedYes

Fingerprint

Tunnel junctions
tunnel junctions
Magnetization
computerized simulation
magnetization
Computer simulation
Multilayers
cells
Exchange coupling
Magnetostatics
Magnetoresistance
magnetostatics
Coercive force
laminates
coercivity
Anisotropy
anisotropy
thresholds

Keywords

  • Computer simulation
  • Magentization flop
  • Magnetic tunnel junction
  • Size effects
  • Synthetic antiferromagnets

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

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title = "Computer simulation of magnetization flop in magnetic tunnel junctions exchange-biased by synthetic antiferromagnets",
abstract = "Computer simulation in a single domain multilayer model is used to investigate magnetization flop in magnetic tunnel junctions, exchange-biased by pinned synthetic antiferromagnets with the multilayer structure NiFe/AlOx/Co/Ru/Co/FeMn. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy and hence increased coercivity of the Co layers in the synthetic antiferromagnet. However, when the synthetic antiferromagnet is not or weakly pinned, the magnetization directions of the two layers sandwiching AlOx, which mainly determine the magnetoresistance, are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal MR change from the high MR state to zero, irrespective of the direction of the free layer switching. This emphasizes an importance of a strong pinning of the synthetic antiferromagnet at small cell dimensions. The threshold field for magnetization flop is found to increase linearly with increasing antiferromagnetic exchange coupling between the two Co layers in the synthetic antiferromagnet. The restoring force from magnetization flop to the normal synthetic antiferromagnetic structure is roughly proportional to the resistance to magnetization flop. Irrespective of the magnetic parameters and cell sizes, the state of magnetization flop does not exist near Ha = 0, indicating that magnetization flop is driven by the Zeeman energy.",
keywords = "Computer simulation, Magentization flop, Magnetic tunnel junction, Size effects, Synthetic antiferromagnets",
author = "Uhm, {Y. R.} and Lim, {Sang Ho}",
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AU - Uhm, Y. R.

AU - Lim, Sang Ho

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N2 - Computer simulation in a single domain multilayer model is used to investigate magnetization flop in magnetic tunnel junctions, exchange-biased by pinned synthetic antiferromagnets with the multilayer structure NiFe/AlOx/Co/Ru/Co/FeMn. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy and hence increased coercivity of the Co layers in the synthetic antiferromagnet. However, when the synthetic antiferromagnet is not or weakly pinned, the magnetization directions of the two layers sandwiching AlOx, which mainly determine the magnetoresistance, are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal MR change from the high MR state to zero, irrespective of the direction of the free layer switching. This emphasizes an importance of a strong pinning of the synthetic antiferromagnet at small cell dimensions. The threshold field for magnetization flop is found to increase linearly with increasing antiferromagnetic exchange coupling between the two Co layers in the synthetic antiferromagnet. The restoring force from magnetization flop to the normal synthetic antiferromagnetic structure is roughly proportional to the resistance to magnetization flop. Irrespective of the magnetic parameters and cell sizes, the state of magnetization flop does not exist near Ha = 0, indicating that magnetization flop is driven by the Zeeman energy.

AB - Computer simulation in a single domain multilayer model is used to investigate magnetization flop in magnetic tunnel junctions, exchange-biased by pinned synthetic antiferromagnets with the multilayer structure NiFe/AlOx/Co/Ru/Co/FeMn. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy and hence increased coercivity of the Co layers in the synthetic antiferromagnet. However, when the synthetic antiferromagnet is not or weakly pinned, the magnetization directions of the two layers sandwiching AlOx, which mainly determine the magnetoresistance, are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal MR change from the high MR state to zero, irrespective of the direction of the free layer switching. This emphasizes an importance of a strong pinning of the synthetic antiferromagnet at small cell dimensions. The threshold field for magnetization flop is found to increase linearly with increasing antiferromagnetic exchange coupling between the two Co layers in the synthetic antiferromagnet. The restoring force from magnetization flop to the normal synthetic antiferromagnetic structure is roughly proportional to the resistance to magnetization flop. Irrespective of the magnetic parameters and cell sizes, the state of magnetization flop does not exist near Ha = 0, indicating that magnetization flop is driven by the Zeeman energy.

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KW - Size effects

KW - Synthetic antiferromagnets

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