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| Exchange Anisotropy of Polycrystalline Ferromagnetic/Antiferromagnetic Bilayers |
| Journal of Magnetics, Volume 7, Number 3, 30 Sep 2002, Pages 80-93 |
Masakiyo Tsunoda*  (Department of Electronic Engineering, Tohoku University), Migaku Takahashi(Department of Electronic Engineering, Tohoku University) |
| Abstract |
| The role of magnetic anisotropy of the antiferromagnetic layer on the magnetization process of exchange coupled polycrystalline ferromagnetic/antiferromagnetic bilayers is discussed. In order to elucidate the magnetic torque response of Ni-Fe/Mn-Ir bilayers, the single spin ensemble model is newly introduced, taking into account the two-dimensionally random distribution of the magnetic anisotropy axes of the antiferromagnetic grains. The mechanism of the reversible inducement of the exchange anisotropy along desirable directions by field cooling procedure is successfully explained with the new model. Unidirectional anisotropy constant, Jk, of polycrystalline Ni-Fe/Mn-Ir and Co-Fe/Mn-Ir bilayers is investigated as functions of the chemical composition of both the ferromagnetic layer and the antiferromagnetic layer. The effects of microstructure and surface modification of the antiferromagnetic layer on JK are also discussed. As a notable result, an extra large value of Jk, which exceeds 0.5 erg/cm2, is obtained for Co70Fe30Mn75Ir25 bilayer with the ultra-thin (50Å∼100Å) Mn-Ir layer. The exchange anisotropy of Co70Fe30Mn75Ir25 100Å bilayer is stable for thermal annealing up to 400℃, which is sufficiently high for the application of spin valve magnetoresistive devices. |
| Keywords: exchange anisotropy; exchange bias; magnetic anisotropy; multilayer; spin valve |
| DOI: |
| Full Text: PDF |
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