Effects of Ru diffusion in exchange-biased MgO magnetic tunnel junctions prepared by in situ annealing

Abstract

We study the effect of Ru diffusion in exchange-biased MgO magnetic tunnel junctions prepared by high-temperature in situ annealing above 400 degrees C, circumventing Mn diffusion conventionally caused by postannealing process. The high temperature in situ annealing leads to Ru diffusion at the CoFeB/Ru interfaces, and thereby results in a reduction in tunnel magnetoresistance (TMR). The minimization of Ru diffusion during the in situ annealing provides a large TMR of 294% at room temperature with an exchange-bias field of 280 Oe. In addition, the temperature and voltage dependence of TMR reveals that there is neither significant spin-exchange scattering nor severe impurity-assisted scattering in the MgO barrier.