Structure and magnetism of Ta/Co/Ta sandwiches

HRTEM and RT magnetometry were used to characterize Ta/Co/Ta sandwiches sputter-deposited on Si(001) wafers. The sandwiches show an intermixed Ta/Co interface region of about 10 Å thickness, which is connected to the presence of a non-ferromagnetic interfacial layer of 6.6 Å thickness per Ta/Co interface. The Co layer has a textured morphology, composed of columns with diameters of about 10-100 Å, and a marked 〈111〉 fee structure with numerous stacking faults. Repetitions of hep stacking sequences are mainly localized in the narrowest columns. The Ta layer shows a short-range ordering characterized by randomly oriented stacks of a few atomic planes about 10-20 Å large.