Investigation on the exchange coupling properties of ring-shaped MnIr/CoFe bilayers

C. C. Chen, M. H. Shiao, Y. C. Lin, H. M. Tsai, C. Y. Kuo, Lance Horng, J. C. Wu, S. Isogami, M. Tsunoda, Migaku Takahashi

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


In this study, the exchange coupling properties of submicron patterned MnIr/CoFe bilayers with strong exchange coupling strength were investigated. The large area of 2.5 mm,×, 2.5 mm of submicron sized bilayer rings were fabricated by electron beam lithography and ion-milling processes. The clear variations of normalized magnetic hysteresis loops of patterned films are the degradation of pinned CoFe at the MnIr/CoFe interfaces and the decrease of exchange bias field, comparing with sheet film. After post-field-annealing treatment, only the exchange field was improved. A magnetic tunnel junction ring with outer diameter/linewidth of 2/0.5 μm was constructed as well to further certify the speculations. The magnetoresistance loops of as-fabricated and post-field annealed MTJ ring revealed that the slightly improved magnetoresistance ratio and exchange field. These results were attributed to the rearrangement of distorted spins at the sample edges. However, in comparison with sheet film, the great degradation of magnetoresistance ratio of patterned device, without respect to as-fabricated or post-field annealed, was not retrieved, revealing that the futility of post-field-annealing treatment to the pinning portion of CoFe layer.

Original languageEnglish
Article number5721802
Pages (from-to)620-623
Number of pages4
JournalIEEE Transactions on Magnetics
Issue number3
Publication statusPublished - 2011 Mar


  • Alternating gradient magnetometer
  • exchange coupling
  • magnetic hysteresis
  • rings

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


Dive into the research topics of 'Investigation on the exchange coupling properties of ring-shaped MnIr/CoFe bilayers'. Together they form a unique fingerprint.

Cite this