N°21 - 23 September 2016 - MUTUAL SYNCHRONIZATION OF SPIN TORQUE NANO-OSCILLATORS THROUGH A NON-LOCAL AND TUNABLE ELECTRICAL COUPLING
The concept of spin torque driven high frequency magnetization dynamics has opened up the field of spintronics to non-linear physics, potentially in complex networks of dynamical systems. In the scarce demonstrations of synchronized spin-torque oscillators, the local nature of the magnetic coupling that is used have largely hampered a good understanding and thus the control of the synchronization process. Here we take advantage of the non-local nature of an electrical coupling to mutually synchronize spin-torque oscillators through their self-emitted microwave currents. The control of the synchronized state is achieved at the nanoscale through two active components of spin transfer torques, but also externally through an electrical delay line. These additional levels of control of the synchronization capability provide new approaches to underlie a large variety of nanoscale collective dynamics in complex networks.
Fig. 1 (a) Scheme of the electrical circuit for the mutual synchronization of two oscillators independently supplied by two currents and connected through the microwave port of two bias tees with a tunable delay line. The detected signal is measured by a spectrum analyzer, connected to the delay with a -6 dBm power splitter (PS). (b) Evolution of the frequency of the interacting STOs as a function of IDC,1 while IDC,2 is fixed to + 10.6 mA. (Bottom) Corresponding spectra for IDC,1= +10.8 mA (1), +11.25 mA (2), +11.8 mA (3) (Non-interacting oscillator properties when one is switched off are in orange and green softened curves).