Magnetic tunnel junctions (MTJs) with low thermal stability at room temperature have been proposed as read units in beyond CMOS computing architectures including stochastic computing unit and probabilistic-bit (p-bit). Networks of multiple interconnected MTJs may face challenges due to potential device-to-device variations in thermal stability from design targets. Recently, we generated tunable telegraphic signals using a thermally stable MTJ through proper control over an external bias field and a dc voltage bias, where we showed that the average dwell times in the antiparallel (AP) and parallel states could be tuned separately. The implication for this method for p-bit designs is that it allows for p-bits to be compatible with the state-of-the-art magnetoresistive random-access memory (MRAM) technology and introduces a second degree of tunability to the input-output characteristics of the device. In this article, we expand on this method in two important ways. First, we demonstrate the applicability of our method to p-bit designs by modeling the transfer function using the existing p-bit models. Our results indicate that the transfer function can be adjusted with slight modifications to the bias field, which allows for the possibility of p-bit circuits capable of on-chip corrections against device-to-device variations in their thermal stabilities. Second, we identify the physical mechanisms that allow for two degrees of tunability in the output signal, which is explained through the Néel-Brown model. This article provides both applicability and predictability to the dual-biasing method.
Bibliographical noteFunding Information:
Manuscript received May 30, 2019; revised September 4, 2019; accepted October 4, 2019. Date of publication November 8, 2019; date of current version November 27, 2019. This work was supported in part by the Center for Probabilistic Spin Logic for Low-Energy Boolean and Non-Boolean Computing (CAPSL), one of the Nanoelectronic Computing Research (nCORE) centers, under Grant 2759.001 and in part by NSF through the Semiconductor Research Corporation (SRC) Program under Grant 1739635. The review of this article was arranged by Editor A. M. P. Anantram. (Corresponding author: Brandon R. Zink.) The authors are with the Department of Electrical and Computer Engineering, University of Minnesota Twin Cities, Minneapolis, MN 55455-0170 USA (e-mail: email@example.com; firstname.lastname@example.org).
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- Dwell time
- magnetic tunnel junction (MTJ)
- probabilistic computing
- stochastic computing
- telegraphic switching
- tunable randomness