Co_(2)MnSi Heusler alloy as magnetic electrodes in magnetic tunnel junctions

摘要

As a consequence of the growing theoretical predictions of 100% spin-polarized half- and full-Heusler compounds over the past six years, Heusler alloys are among the most promising materials class for future magnetoelectronic and spintronic applications. We have integrated Co_(2)MnSi, as a representative of the full-Heusler compound family, as one magnetic electrode into magnetic tunnel junctions. The preparation strategy has been chosen so as to sputter Co_(2)MnSi at room temperature onto a V-buffer layer, which assists in (110) texture formation, and to deposit the Al-barrier layer directly thereafter. After plasma oxidizing the Al-barrier layer, subsequent annealing leads (1) to the texture formation and (2) to the appropriate atomic ordering within the Co_(2)MnSi, and (3) homogenizes the AlO_(x) barrier. It is shown that the magnetic switching of the ferromagnetic electrodes is well controlled from room temperature down to 10 K. The resulting tunnel magnetoresistance-effect amplitude of the Co_(2)MnSi containing magnetic tunnel junctions has been determined as a function of temperature and the spin polarization of the Co_(2)MnSi Heusler compound has been estimated to be 61% at 10 K. Thus, the spin polarization of the Co_(2)MnSi layer at 10K exceeds that of conventional transition metals.