Exchange bias in biaxial and uniaxial systems has been micromagnetically simulated for a system containing more than 250 000 elements. Each ferromagnetic element was coupled to a neighboring antiferromagnetic grain that rotated uniformly under the effect of thermal fluctuations. The time evolution of the ferromagnetic moments was determined by solving the Landau-Lifshitz-Gilbert equation for each degree of freedom. For a sample of $\mathrm{NiFe}$ (thickness of $250\mathrm{\AA }$) coupled to polycrystalline $\mathrm{NiMn}$ (thickness of $500\mathrm{\AA }$) we obtained an exchange bias of $118\mathrm{Oe}$ and an enhanced coercivity of $108\mathrm{Oe}$. There is good agreement with experiment despite the absence of adjustable parameters. The simulation also correlates the symmetry of the antiferromagnet to the loop shape and training effect.

• Received 12 October 2005

DOI:https://doi.org/10.1103/PhysRevB.73.104433