Spin torque oscillator (STO) is a tiny magnetic layer stack which oscillates in microwave frequency range simply by injecting a DC current. However, the performance of a single STO, such as power level and frequency stability, is not good enough for practical application. Some past works observed mutual phase locking between two STOs formed close to each other. It was found that a mutually phase locked STO pair shows significantly better performance than a single STO. Therefore, it is a natural extension to try to synchronize multiple STOs for even better performance, but to the author’s knowledge, no research group has published any success of such an attempt as of 2008.
It is believed that interaction between spin waves and a STO is the underlying mutual phase locking mechanism. One STO launches spin waves as it oscillates, and the oscillation of the other STO is synchronized to the incident spin wave. However, spin wave propagation is much more complicated than usual 2D wave propagation such as membrane vibration, and so far no quantitative study has been conducted either experimentally or theoretically.
We have a Kerr imaging system for capturing spin wave propagation. The goal of this project is to study the interaction between the incident spin wave and STO by using this system in order to understand the mutual phase locking mechanism quantitatively, and eventually gain new insight for designing and characterizing multiple STO synchronization devices.
Publications with Ricketts Lab
R. Birt, K. An, M. Tsoi, S. Tamaru, D. Ricketts, K. L. Wong, P. K. Amiri, K. L. Wang, and X. Li, “Deviation from exponential decay for spin waves excited with a coplanar waveguide antenna,” Applied Physics Letters., vol. 101, no. 25, pp.252409, 2012.
S. Tamaru and D. S. Ricketts, “Experimental Study of the Variation in Oscillation Characteristics of Point-Contact-Based Spin-Torque Oscillators.” IEEE Trans. on Magnetics, vol.3, no., pp.3000504, 2012
D. Birt, K. An, M. Tsoi, S. Tamaru, D. Ricketts, K.L. Wong, P.K. Amiri, K.L. Wang and X. Li,” Oscillatory Spatial Intensity Pattern for Spin Waves Excited with a Coplanar Waveguide Antenna,” Conference on Magnetism and Magnetic Materials, Chicago, IL, paper EC-02, Jan. 2013.
S. Tamaru and D. S. Ricketts, “Origin of variation in the oscillation characteristics of point contact based spin torque oscillators,” Magnetics Letters, IEEE , vol.3, no., pp.3000504, 2012
W. Hu, Y. Tang, Y.Zhang, J. Gu, S. Tamaru, J. A. Bain, L. R. Carley, R. F. Davis, G. K. Fedder and D. S. Ricketts, “TI/TIO2 nanodevice fabrication using compliant probes and CMOS probe-arrays,” Technologies for Future Micro-Nano Manufacturing, Napa Valley, CA, Aug. 2011.
W. Hu, S. Tamaru, J. A. Bain and D. S. Ricketts, “High Current Pulse Generation for Thermal Surface Modification using Standard STM,” Int. Conf. Electron, Ion, Photon Beam Technology and Nanofabrication, May. 2011.
S. Tamaru and D. S. Ricketts, “Influence of the bias field orientation on the interaction strength between two closely formed spin torque oscillators,” Int. Magnetics Conf., paper CO-05, Taiwan, Apr 2011.
E.R. Evarts, R.A. Booth, L.R. Shah, Y. Tang, S. Tamaru, D.S. Ricketts, J.A. Bain, S.A. Majetich,”Sub-30 nm Magnetic Tunnel Junction and Spin Valve Nanopillar Analysis Using Conductive Atomic Force Microscopy,” Int. Magnetics Conf., paper BB-03, Taiwan, Apr 2011.
D. S. Ricketts, L. Cao and S. Tamaru, “Spin-torque oscillator arrays as a solution for line width reduction in RF applications”, Conference on Magnetism and Magnetic Materials, paper EY-01, Washington D.C., Dec. 2009.