Toggling synchronization of nano-contact spin torque oscillators with spin wave beams*

The synchronization of multiple nano-contact spin torque oscillators (NC-STOs) [1-3] is mediated by propagating spin waves (SWs) [4]. Furthermore, it has been shown that the Oersted field in the vicinity of the NC can induce highly directional SW beams [5, 6]. Not only have we recently demonstrated the robust synchronization between two oscillators separated by over 1 micron, but also the driven synchronization of up to five oscillators by purposefully taking advantage of such SW beams [7]. Here, we demonstrate that when the NC diameters differ by a significant amount, the Oersted field scale in such a way as to promote or block synchronization depending on the SW propagation direction, allowing one to easily toggle between synchronized and un-synchronized states by simply altering the applied field direction. [1] S. Kaka, \textit{et al.}, Nature \textbf{437}, 389 (2005). [2] F.B. Mancoff, \textit{et al.}, Nature \textbf{437}, 393 (2005). [3] S.R. Sani, \textit{et al.}, Nat. Comm. \textbf{4}, 2731 (2013). [4] M.R. Pufall, \textit{et al.}, Phys. Rev. Lett. \textbf{97}, 087206 (2006). [5] R.K. Dumas, \textit{et al.}, Phys. Rev. Lett. \textbf{110}, 257202 (2013). [6] M.A. Hoefer, \textit{et al.}, Phys. Rev. B, \textbf{77}, 144401 (2008). [7] A. Houshang, \textit{et al.}, \textit{Nature Nanotechnol., }in press$.$