Modelling of Spin Torque Nano-Oscillators with perpendicular polarizer and planar free layer

Spin Torque Nano-Oscillators (STNO) promise improvements in different areas of technology like wireless communications and machine learning. The basics of the physics of a single one of these spintronic devices is relatively well understood, but it is still necessary to comprehend in a fundamental manner how the synchronization of a coupled network of these devices works. This is a complex task because of the large range of parameters (geometrical, electric, magnetic...) that come into play, the non-linearity of the dynamics and the different coupling states that can result from the interaction. In this thesis, that will continue with a PhD, numerical simulations of the Landau-Lifshitz-Gilbert equation (LLG equation), were performed to understand the physics of a specific structure of STNO: one with a perpendicular polarizer, and an out-of-plane external magnetic field. In the first place a single device was studied. It was found that the dimensions of the oscillator can affect a lot its dynamics, which is evidenced in a change of the static and dynamic regions in the Voltage-Field-Frequency diagrams (VFH diagrams). Moreover, the results suggest that it is possible to tune the coupling due to the dipolar interaction without changing the frequency of the device. Secondly, injection locking with an external RF signal was considered for devices of different dimensions and modes, and the phase locking bandwidth was evaluated. In the third place, the coupling between two STNOs was studied. In this case, the separation between the oscillators changed the VFH diagrams like the case of a single oscillator when its symmetry is modified. Besides, the voltage and magnetic field were varied differently in each oscillator and for each value of these parameters, synchronization was evaluated. A common characteristic in these three situations is that when sweeping though different values of the external field, the applied voltage or the RF frequency, hysteresis effects were found to influence the dynamic state of the oscillator and its synchronization.