Ultrafast and low-energy switching in voltage-controlled elliptical pMTJ

TL;DR

This paper presents an elliptical pMTJ design that enables ultrafast, low-energy magnetization switching without external magnetic fields, using a bias layer to generate the necessary magnetic field, demonstrated through macrospin simulations.

Contribution

The study introduces a novel elliptical pMTJ structure with an integrated bias layer to eliminate external magnetic field requirements for VCMA switching.

Findings

Achieves 0.38 ns switching time at 0.3 fJ energy

Provides a 50 mT bias magnetic field via the bias layer

Supports low-voltage operation around 1 V

Abstract

Switching magnetization in a perpendicular magnetic tunnel junction (pMTJ) via voltage controlled magnetic anisotropy (VCMA) has shown the potential to markedly reduce the switching energy. However, the requirement of an external magnetic field poses a critical bottleneck for its practical applications. In this work, we propose an elliptical-shaped pMTJ to eliminate the requirement of providing an external field by an additional circuit. We demonstrate that a 10 nm thick in-plane magnetized bias layer (BL) separated by a metallic spacer of 3 nm from the free layer (FL) can be engineered within the MTJ stack to provide the 50 mT bias magnetic field for switching. By conducting macrospin simulation, we find that a fast switching in 0.38 ns with energy consumption as low as 0.3 fJ at a voltage of 1.6 V can be achieved. Furthermore, we study the phase diagram of switching probability, showing that a pulse duration margin of 0.15 ns is obtained and a low-voltage operation (~ 1 V) is favored. Finally, the MTJ scalability is considered, and it is found that scaling-down may not be appealing in terms of both the energy consumption and the switching time for the precession based VCMA switching.