Nuclear Magnetic Resonance Reveals Structural Evolution Upon Annealing In Epitaxial Co2mnsi Heusler Films

Co2MnSi films were recently reported to show a significant increase in current-perpendicular-to-plane-giant-magnetoresistance upon annealing. Here, nuclear magnetic resonance was used to study the impact of annealing on the structure of such films. Below 550 degrees C, no long-range L2(1)-order is observed, while annealing above 550 degrees C leads to the formation of the ideal L2(1) configuration, however, with a distinct degree of off-stoichiometry. Further evidence from restoring field measurements hints that interdiffusion may account for the drop in magnetoresistance observed for samples annealed above 600 degrees C. These results show that optimizing films for spintronics involves the identification of the best annealing temperature, high enough for long-range order to emerge, but low enough to maintain smooth interfaces. (C) 2013 AIP Publishing LLC.