Abstract
Reliable manipulation of magnetic droplets is of immense importance for their applications in spin torque oscillators. Using micromagnetic simulations, we find that the antiphase precession state, which originates in the dynamic dipolar interaction effect, is a favorable stable state for two magnetic droplets nucleated at two identical nano-contacts. A magnetic field pulse can be used to destroy their stability and merge them into a big droplet. The merging process strongly depends on the pulse width as well as the pulse strength.
Highlights
Spin torque oscillators (STOs) with nanoscale electrical contacts (NCs) have attracted great attentions due to their application in microwave generation.[1,2,3,4,5] Under sufficiently large currents, the intrinsic damping torque can be compensated by the spin-transfer torque (STT)[6,7] generated in such contacts in the free layer of spin valves or magnetic tunnel junctions, giving rise to coherent oscillations
A strongly self-localized oscillation mode the dissipative droplet soliton has been theoretically predicted[12,13] and experimentally observed in a NC-STO that has a free layer with perpendicular magnetic anisotropy (PMA).[14,15]
We found that two magnetic droplets nucleated at two identical NCs could lose stability and merge into a larger single droplet when the energy balance is destroyed.[23]
Summary
Spin torque oscillators (STOs) with nanoscale electrical contacts (NCs) have attracted great attentions due to their application in microwave generation.[1,2,3,4,5] Under sufficiently large currents, the intrinsic damping torque can be compensated by the spin-transfer torque (STT)[6,7] generated in such contacts in the free layer of spin valves or magnetic tunnel junctions, giving rise to coherent oscillations. We further study the merging process triggered by a magnetic field pulse. A magnetic field pulse Hp is used to trigger the merging process of droplets. The magnetization dynamics of the free layer is described by the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation:[6,25] dm dt. We ignored thermal effects and the current-induced Oersted field
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