Engineering of Voltage-Controlled Magnetic Anisotropy Magnetic Tunnel Junctions at Cryogenic Temperatures

We identified through numerical simulations the optimal condition to have a deterministic switching regime assisted by voltage-controlled magnetic anisotropy (VCMA). To minimize the write energy required to reach this regime, we measure the VCMA coefficient
$\xi $
on perpendicular magnetic tunnel junctions (pMTJ) with high resistance area (RA) product and varying thicknesses of the FeCoB storage layer and the naturally oxidized tunnel barrier. The VCMA coefficient is higher as the effective anisotropy decreases, which is the case for larger Mg and FeCoB thicknesses. The temperature dependence of
$\xi $
was shown to increase from room temperature to 5 K, showing values up to 35 fJ/Vm at 10 K.