Estimation of spin transfer torque effect and thermal activation effect on magnetization reversal in CoFeB∕MgO∕CoFeB magnetoresistive tunneling junctions

Abstract

In the CoFeB∕MgO∕CoFeB magnetoresistive tunneling junctions, the bias-dependent magnetic switching curves are investigated and the spin transfer torque effect and the thermal activation effect on the magnetic switching are estimated. The different switching behaviors at the positive and negative biases were observed, which are the asymmetric changes of the coercive force and the shift field. In order to investigate the asymmetric reduction of the coercive force according to the bias direction, the magnetic excitation effect due to the hot electron was introduced. Consequently, from the analysis by using the current versus magnetic field phase diagram, the asymmetric reduction of the coercive force at the positive and negative biases was explained quantitatively by the relationship between the thermal activation effect due to the Joule heating and the magnetic excitation effect due to the hot electron.