Co2MnSi Heusler alloy as magnetic electrodes in magnetic tunnel junctions

Kämmerer S, Thomas A, Hütten A, Reiss G. Co2MnSi Heusler alloy as magnetic electrodes in magnetic tunnel junctions. APPLIED PHYSICS LETTERS. 2004;85(1):79-81.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 Co2MnSi, 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 Co2MnSi 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 Co2MnSi, and (3) homogenizes the AlOx 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 Co2MnSi containing magnetic tunnel junctions has been determined as a function of temperature and the spin polarization of the Co2MnSi Heusler compound has been estimated to be 61% at 10 K. Thus, the spin polarization of the Co2MnSi layer at 10K exceeds that of conventional transition metals. (C) 2004 American Institute of Physics