Magnetization configurations of a tri-layer nanopillar ferromagnet/nonmagnetic spacer/ferromagnet

The equilibrium magnetization configurations of tri-layer circular nanopillar are calculated within micromagnetic approach. Nanopillar is assumed to be a vertical stack of ferromagnetic/nonmagnetic/ferromagnetic layers. The regions of geometrical parameters of nanopillar (radius and thickness), where the magnetic vortices and single domain states appear in the ground state, are calculated analytically and checked by micromagnetic simulations. The interlayer magnetostatic coupling affects essentially the formation of vortices or single domain states in both ferromagnetic layers. A considerable influence of the thicknesses of the ferromagnetic layers and spacer on the stability of vortex states is found. The results can be applied to interpret experiments on spin torque induced magnetization dynamics in nanopillars and tunnel junctions and also to estimate the nanopillar ground states. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4706560]