Enhancement of the thermal stability of magnetic tunnel junctions employing artificial ferrimagnets

We have fabricated magnetic tunnel junctions that use Co/Ru/Co and Co/Ru/Co 50Fe50 artificial ferrimagnet (AFi) systems as hard magnetic electrodes and AlOx as tunnel barrier. The thermal behavior of the two AFis, incorporated in tunnel junctions, presents dramatic differences, the most remarkable be ing the much greater thermal stability of the Co/Ru/CoFe system. This stems from the improvement of the interfaces the CoFe alloy forms with its adjac ent Ru and AlOx layers. After successive annealing steps up to 400 degreesC , junctions incorporating the Co/Ru/CoFe system still present a significant tunnel magnetoresistance signal of nearly 20%, and most importantly, an al most intact magnetic rigidity of the hard magnetic system, being very promi sing for spin-electronic devices. (C) 2000 American Institute of Physics. [ S0003-6951(00)02048-9].