Thermal effects in spin torque switching of perpendicular magnetic tunnel junctions at cryogenic temperatures

TL;DR

This study investigates how cryogenic temperatures affect spin torque switching in perpendicular magnetic tunnel junctions, revealing that junction heating and stochastic switching persist down to 4 K due to reduced thermal conductivity.

Contribution

It provides a systematic analysis of temperature effects on spin torque switching probability in nanopillar junctions from room temperature to 4 K, highlighting the role of thermal properties.

Findings

Switching probability remains stochastic at 4 K.

Junction temperature saturates below 75 K due to heating.

Reduced thermal conductivity affects heat flow in the junction.

Abstract

Temperature plays an important role in spin torque switching of magnetic tunnel junctions causing magnetization fluctuations that decrease the switching voltage but also introduce switching errors. Here we present a systematic study of the temperature dependence of the spin torque switching probability of state-of-the-art perpendicular magnetic tunnel junction nanopillars (40 to 60 nm in diameter) from room temperature down to 4 K, sampling up to a million switching events. The junction temperature at the switching voltage---obtained from the thermally assisted spin torque switching model---saturates at temperatures below about 75 K, showing that junction heating is significant below this temperature and that spin torque switching remains highly stochastic down to 4 K. A model of heat flow in a nanopillar junction shows this effect is associated with the reduced thermal conductivity and heat capacity of the metals in the junction.