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Dynamical influence of vortex–antivortex pairs in magnetic vortex oscillators

2015; Elsevier BV; Volume: 394; Linguagem: Inglês

10.1016/j.jmmm.2015.06.057

1873-4766

R. M. Otxoa, S. Petit, Mauricio Manfrini, Iuliana Radu, Aaron Thean, Joo-Von Kim, T. Devolder,

Quantum and electron transport phenomena

We study the magnetization dynamics in a nanocontact magnetic vortex oscillators as function of temperature. Low temperature experiments reveal that the dynamics at low and high currents differ qualitatively. At low currents, we excite a temperature independent standard oscillation mode, consisting of a gyrotropic motion of a vortex about the nanocontact in the free layer. Above a critical current, a sudden jump in the frequency is observed, which occurs with a substantial increase of the frequency versus current slope factor. Using micromagnetic simulation and analytical modeling, we associate this new regime to the creation of a vortex–antivortex pair in the pinned layer of the spin valve. This pair gives an additional perpendicular spin torque component that alters the free layer vortex dynamics, which can be quantitatively accounted for by an analytical model.