Challenges and Strategies for Using Spin Torque Oscillators for Practical Microwave Applications

Speaker: Shingo Tamaru
Affiliation: National Institute of Advanced Industrial Science and Technology (AIST)

Abstract: Spin torque oscillator (STO) is an emerging device that can generate a microwave signal simply by injecting a DC current. It is expected to serve as a microwave signal source in radio frequency (RF) integrated circuits due to many beneficial features such as its simple structure, tiny dimension, and compatibility with CMOS processes and so on. However, various performance indicators have to satisfy industry specifications in order for a STO to be used for such applications. One of the most serious performance problems is its poor frequency stability, i.e. large phase noise. The phase noise levels of STOs are far larger than required for most microwave applications, thus need to be largely reduced.  For this purpose, we recently developed a phase locked loop (PLL) circuit custom designed to stabilize a STO, and successfully demonstrated stable phase locked oscillation, characterized by an extremely sharp peak at the target frequency [1]. While we believe this accomplishment is a major milestone for the productization of STOs, its residual phase noise is still significantly larger than commercial PLL circuits consisting of a transistor based amplifier and external resonator, thus further improvement is crucial [2].

In this talk, I will present the performance of the STO stabilized by PLL, sources of residual phase noise, and future strategies for further improving the phase noise performance to compete with commercial PLL circuits.

 [1] S. Tamaru et al., Sci Rep. 5, 18134 (2015)

[2] S. Tamaru et al., Appl. Phys. Express, 9, 053005 (2016)

Biography: Shingo Tamaru received the Ph.D. degree in Electrical and Computer Engineering Department of Carnegie Mellon University (CMU) in 2005. Then he joined Seagate Technology Pittsburgh Research Center as a research staff member and was engaged in first ferroelectric probe storage project and next heat assisted magnetic recording project. In 2009, he moved to CMU as a project scientist and studied spin wave physics and spin torque oscillator. He moved back to Japan in 2012, and joined Advanced Industrial Science and Technology (AIST) in Tsukuba, Japan as an invited senior researcher. His research interests include high frequency Spintronics, magnetization dynamics and magnetic recording technology.

For more information, contact Prof. Kang Wang ()

Date(s) - Jun 02, 2016
2:00 pm - 3:00 pm

E-IV Faraday Room #67-124
420 Westwood Plaza - 6th Flr., Los Angeles CA 90095