Recently, magnetic tunnel junctions (MTJs) with superparamagnetic free layers (sMTJs) have been proposed as key components in probabilistic bits (p-bits). However, the average fluctuation rates of sMTJs are very sensitive to slight variations in the device dimensions, which creates a major obstacle to their realization in large-scale networks. One possible solution is to implement dual-biasing on p-bits to offset the effects of variations through onboard corrections. In our previous work, we demonstrated that dual-biasing has the unique capability of separate control over the high- and low-state dwell times, which adds an extra degree of tunability in the signals generated. However, these studies investigated dual-biasing on thermally stable MTJs; therefore, the maximum switching rates were lower than the gigahertz rates desired for sMTJ-based p-bit circuits. While dual-biasing on sMTJs rather than thermally stable MTJs would improve the switching rates, some of the flexibility and robustness of dual-biasing may be sacrificed due to the sensitivity of sMTJs. In this letter, we applied the dual-biasing method on 10 MTJs with varying thermal stability factors to test if sMTJs can achieve the same degree of separation between high- and low-state dwell-time tunability as thermally stable MTJs. Our results show that two degrees of tunability was achieved on all MTJs tested, thus demonstrating that dual-biased p-bits can achieve switching rates equal to or greater than single-biased sMTJs.
Bibliographical noteFunding Information:
This work was supported in part by the Center for Probabilistic Spin Logic for Low-Energy Boolean and Non-Boolean Computing, one of the Nanoelectronic Computing Research centers as task 2759.001, and in part by the Semiconductor Research Corporation program sponsored by the National Science Foundation under Grant 1739635. The authors thank Dr. Yang Lv for useful disscussion.
© 2010-2012 IEEE.
- magnetic tunnel junctions
- Spin electronics
- spin torque
- thermal stability
- tunneling magnetoresistance