Evidence for strong magnon contribution to the TMR temperature dependence in MgO based tunnel junctions

Abstract

We have prepared MgO based magnetic tunnel junctions which show up to 143% tunneling magnetoresistance (TMR) ratio at room temperature and 205% at $12\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. This TMR temperature dependence is mainly caused by a strong temperature dependence in the antiparallel magnetic state, while in the parallel state the change of condunctance is small. We found that a modified version of the magnon excitation model may be applied to these MgO magnetic tunnel junctions. If the thermal smearing of the tunneling electron's energy is included it is possible to fit the temperature dependence. We will show the results for our data and we have also tested our model successfully on data from other publications.