Unconventional computing with voltage-controlled magnetic tunnel junctions

This talk will discuss electric-field-controlled magnetic tunnel junction (MTJ) devices for magnetic random access memory (MRAM), which utilize the voltage-controlled magnetic anisotropy (VCMA) effect for switching. We present the first VCMA-MRAM devices with sub-1V write voltage, based on perpendicular MTJs with record-high VCMA coefficients (~130 fJ/Vm), high tunnel magnetoresistance ratio (TMR > 150%), and small bit diameters of 30 to 70 nm [1]. Next, we discuss the application of these VCMA-MRAM bits for applications ranging from true random number generation to machine learning [2], physically unclonable functions [3], and implementation of probabilistic computers to solve hard optimization problems [4]. As an example of the latter, we demonstrate solution of 40-bit integer factorization problems on Ising machines that utilize experimental stochastic bitstreams from VCMA-controlled MTJs. [1] Y. Shao et al., Communications Materials 3, 87 (2022) [2] Y. Shao et al., IEEE Magnetics Letters 12, 4501005 (2021) [3] Y. Shao et al., Advanced Electronic Materials, 2300195 (2023) [4] Y. Shao et al., Nanotechnology, doi: 10.1088/1361-6528/acf6c7 (2023)