High-Frequency Switching in Superparamagnetic Magnetic Tunnel Junctions by Enhancing Damping

TL;DR

This paper demonstrates that increasing magnetic damping in superparamagnetic tunnel junctions accelerates thermal switching, with voltage-controlled exchange coupling offering better high-frequency control than spin-transfer torque.

Contribution

It systematically investigates the effect of damping on switching rates and compares control mechanisms, highlighting VCEC's advantages for high-frequency applications.

Findings

Enhanced damping increases thermal switching rates.

VCEC maintains control efficiency under high damping.

STT switching is suppressed at high damping.

Abstract

Superparamagnetic magnetic tunnel junctions (sMTJs) are promising components for true random number generation and probabilistic computing. Achieving high-frequency fluctuation while maintaining reliable control over output level is critical for applications. In this work, we systematically investigate the role of magnetic damping in regulating thermal switching rates using macrospin simulations. We show that enhanced damping accelerates the switching rate by increasing the escape rate over the energy barrier. We further compare two control mechanisms: spin-transfer torque (STT) and voltage-controlled exchange coupling (VCEC). Our results reveal that STT-based switching is strongly suppressed under high damping, whereas VCEC, by reshaping the energy landscape without relying on torque-driven dynamics, retains high control efficiency. These findings suggest that enhanced damping not only enables faster stochastic switching in sMTJs but also makes VCEC inherently better suited than STT for high-frequency applications.