Dresden 2003 – scientific programme

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MA: Magnetismus

MA 8: Magnetische Kopplungsph
änomene / Exchange Bias

MA 8.9: Talk

Monday, March 24, 2003, 17:15–17:30, HSZ/405

Antiferromagnetic Rotational Energy Loss in Exchange Coupled CoFe/IrMn and NiFe/IrMn Thin Films — •Klaus Steenbeck, Roland Mattheis, and Marco Diegel — Institut für Physikalische Hochtechnologie, Winzerlaer Str. 10, 07745 Jena

The energy loss of coupled ferromagnetic(F)/antiferromagnetic(AF) polycrystalline film systems by in-plane rotation of the F magnetization in a high magnetic field was measured by torque magnetometry in the temperature range of 10 K to 300 K, in order to get deeper insight in the mechanism of exchange anisotropy. High field rotational energy losses can originate from irreversible switches of the AF order as discussed, for example, by M. D. Stiles [1] and M. Tsunoda [2]. We have sputtered Ta/NiFe 20 nm/IrMn t_AF/Ta and Ta/CoFe 20 nm/IrMn t_AF/Ta films with high reproducibility in a UHV plant and determined their interface coupling energy density J, exchange bias field and magnetization by torque magnetometry, MOKE and VSM. J and the integral energy loss per area E_2π, after complete rotation of the magnetization in a field H=5 kOe, were measured as a function of the IrMn film thickness t_AF and temperature. We analyse our experimental results in the frame of a new theoretical model in which independent AF grains couple to the F film by net moments, which are determined by a statistical Gaussian distribution of n spins at the F/AF interface.

[1] M. D. Stiles and R. D. McMichael, Phys. Rev. B 59, 3722 (1999).

[2] M. Tsunoda and M. Takahashi, J. Magn. Magn. Mater. 239, 149 (2002).