In a nanopillar with dipolarly coupled vortices, we present an experimental and simulation study to understand how the interplay between the bias field and spin transfer torque impacts reversal of the vortex cores. We find that, depending on the current values, vortex cores might experience different physical mechanisms for their reversal, namely a static or a dynamic switching. We believe that our results might be useful in the context of vortex based non volatile memories, as a current controlled selective core switching is proposed .

The domain walls dynamics and generation and evolution of magnetic inhomogeneities of soliton type, emerging in a thin flat layer with the parameters of the magnetic anisotropy, which are different from other two thick layers of the five-layer ferromagnetic structure, were investigated.

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With the generalized Landau-Lifshitz equation the dynamics of the magnetization in the permalloy nanopillars of small diameter of 120 nm is studied. For the numerical calculation of the magnetic vortices bound dynamics a software package for micromagnetic simulations SpinPM was used. The nanopillars have two magnetic layers separated by a nonmagnetic layer. The study of two coupled magnetic vortices dynamics under the influence of an external magnetic field perpendicular to the plane of the sample and polarized electric current was conducted. The coupled magnetic vortices were taken with the same polarity and chirality. By using micromagnetic simulation the dependence of the magnetic field, switching the polarity of the vortex core in thin and thick layers, on the current strength was found. For the case of low currents, the vortex polarity switch in thin and thick layers was observed with a low exit of the vortex from the geometric center. For the case of high currents, the dynamic mechanism for the vortex core polarity switching was observed for a vortex in a thick layer for all values of the current polarization. For the vortex in a thin layer the dynamic mechanism of the vortex core polarity switching was observed only for the case of a large polarization. The minimum current value in the high current region (similarly to the case of nanocylinder with a diameter of 200 nm) significantly decreases with the increase of the current polarization value.