Annealing effect on structural and magnetic properties of Ta/Cu/FeMn/Co/FeMn/Ta thin film structures

We report on the annealing effect on the structural and magnetic properties of Ta-5nm/Cu-5nm/FeMn8nm/Co-8nm/FeMn8nm/Ta-5nm samples prepared by sputter ing, on silicon substrate, at room temperature. For the as-deposited sample s the interfacial exchange anisotropy field (H-e) between the Co and FeMn l ayers is about 95 Oe. It increases sensitively with annealing to reach a ma ximum value of 135 Oe at 240 degrees C annealing temperature. Above this te mperature, we observe a strong decrease of H-e, down to 90 Oe after anneali ng at 280 degrees C, and an increase of 50% of the saturation magnetization . In order to understand the effect of the annealing on the magnetic proper ties, we performed a detailed structural analysis by means of Rutherford ba ck scattering spectroscopy (RBS), nuclear magnetic resonance (NMR), and tra nsmission electron microscopy (TEM). All these techniques attribute the lar ge changes in the magnetic properties to the formation of a new ferromagnet ic FeMnCo phase at the FeMn/Co interfaces.