Spin-electronic devices with half-metallic Heusler alloys

We have integrated Co 2MnSi as a representative of the full-Heusler compound family as one magnetic electrode into technological relevant magnetic tunnel junctions. The resulting tunnel magnetoresistance at 20 K currently achieved is 108% associated with a Co 2MnSi spin polarization of 70% clearly proving that Co 2MnSi is already superior to 3d-based magnetic elements or their alloys. The corresponding room temperature value of the tunnel magnetoresistance is 42%. The presence of a step like tunnel barrier which is already created during plasma oxidation, while preparing the AlO x tunnel barrier, has been identified as the current limitation to achieve larger tunnel magnetoresistance and hence larger spin polarization and is a direct consequence of the oxygen affinity of the Co 2MnSi-Heusler element Mn. In addition preliminarily results on Co 2FeSi as a new full-Heusler compound integrated as magnetic electrode into technological relevant magnetic tunnel junctions are shown and discussed.