Figure 4 : Fine splitting of vortex gyration frequencies.

From: Spin-torque-induced dynamics at fine-split frequencies in nano-oscillators with two stacked vortices

Figure 4

(a) Experimentally obtained frequencies measured around zero field. The modes were measured at a sample current of −10 mA. The frequencies obtained by micromagnetic simulations including the spin-transfer torque are shown in b for values of the spin-polarization P between 0.5 and 0.6, where the dashed lines are guides to the eye. The simulations reveal the displayed fine structure of frequencies, which are in one-to-one correspondence with the experimentally measured values. According to the simulations, the fine structure results from two distinct splittings. The first fine splitting is defined by the relative alignment between the top vortex and the Oersted field (HOe) vorticities. This is apparent from a, where the insets indicate the vorticities of the Oersted field and the top vortex for the respective branches of the fine structure. A further hyperfine splitting is due to the relative orientation of the vortex core polarities, which are illustrated by the red and grey arrows. Note, that throughout a and b, data points referring to identical OV–DV combinations are represented by symbols of the same colour.