BD-07: Magnetic droplet soliton pairs

Magnetic droplets are dissipative solitons found in perpendicular magnetized materials where a spin current counteracts the inherent damping. A typical device for droplet studies is the spin torque nano-oscillator, where a thick reference layer (RL) polarizes the applied current, which exert a torque on the free layer (FL) leading to the nucleation of a soliton. Droplets in these devices have been the subject of a large number of experimental and theoretical reports [1, 2]. However, the research has only been focused on magnetic excitations in the free layer. Here, we show that droplets form also in the reference layer at sufficient high currents. The experimental signature of droplet pairs (DP) is a clear decline in the resistance accompanied with strong low-frequency noise (Fig. 1). We use the measured data to construct a phase diagram of the magnetic states as a function of applied field and current. Furthermore, we use micromagnetic simulations to get more detailed insight in the droplet pair state. Figure 2 presents an example of the results. The simulations reveal that the dynamics of coexisting droplets can be described as periodic, pseudo-periodic or chaotic. The coexisting droplets are strongly interacting and constitute a platform for studies of non-linear soliton pair dynamics.References: [1] Macià F., and Kent A. D. (2020). Magnetic droplet solitons. J. Appl. Phys., 128, 100901 [2] Sulymenko O. R., Prokopenko O. V., Tyberkevych V. S., Slavin A. N., and Serga A. A. (2018). Bullets and droplets: Two-dimensional spin wave solitons in modern magnonics (Review Article), Low Temp. Phys. 44, 602