PUB - Publikationen an der Universität Bielefeld

The transport properties of Co2MnSi/AlOx/Co-Fe magnetic tunnel junctions showing a tunnel magnetorestistance of 95% at low temperatures are discussed with respect to temperature-dependent magnetic moments at the Co2MnSi/AlOx interface and electronic band structure effects. These junctions show a considerably larger temperature and bias voltage dependence of the tunneling magnetoresistance compared to Co-Fe-B/AlOx/Co-Fe-B junctions, although the effective spin polarization of Co2MnSi (66%) is larger than Co-Fe-B (60%). Especially, the tunnel magnetoresistance of the Co2MnSi based junctions becomes inverse for large bias voltages. With increasing atomic disorder of the interfacial Co2MnSi its magnetic moments decrease and show a stronger temperature dependence. Even for the best atomic ordering achieved the corresponding spin-wave parameters of Mn and Co at the Co2MnSi/AlOx interface are significantly larger than expected for Co2MnSi bulk and also larger than the spin-wave parameters of Co and Fe at a Co-Fe-B/AlOx interface. The influence of enhanced interfacial magnon excitation in the Co2MnSi/AlOx/Co-Fe junctions on their transport properties will be discussed as well as possible origins for the negative tunnel magnetoresistance at high bias voltages.