Spin-electronic devices with half-metallic Heusler alloys

We have integrated Co2MnSi 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 Co2MnSi spin polarization of 70% clearly proving that Co2MnSi 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 AlOx 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 Co2MnSi-Heusler element Mn. In addition preliminarily results on Co2FeSi as a new full-Heusler compound integrated as magnetic electrode into technological relevant magnetic tunnel junctions are shown and discussed.