Hrkac, V.; Lage, E.; Köppel, G.; Strobel, J.; McCord, J.; Quandt, E.; Meyners, D.; Kienle, L.: Amorphous FeCoSiB for exchange bias coupled and decoupled magnetoelectric multilayer systems: Real-structure and magnetic properties. Journal of Applied Physics 116 (2014), p. 134302/1-7

The effect of field annealing for exchanged biased multilayer films is studied with respect to the resultant structural and magnetic film properties. The presented multilayer stacks comprise repeating sequences of Ta/Cu/{1 1 1} textured antiferromagnetic Mn70Ir30/amorphous ferromagnetic Fe70.2Co7.8Si12B10. Within the ferromagnetic layers crystalline filaments are observed. An additional Ta layer between the antiferromagnet and ferromagnet is used in order to investigate and separate the influence of the common Mn70Ir30/Fe70.2Co7.8Si12B10 interface on the occurring filaments and structural changes. In situ and ex situ transmission electron microscopy is used for a comprehensive structure characterization of multilayer stacks for selected temperature stages. Up to 250 C, the multilayers are structurally unaltered and preserve the as-deposited condition. A deliberate increase to 350 C exhibits different crystallization processes for the films, depending on the presence of crystal nuclei within the amorphous ferromagnetic layer. The influence of volume-to-surface ratio of the multilayer stacks to the crystallization process is emphasized by the comparison of in situ and ex situ investigations as the respective specimen thickness is changed. Complementary magnetic studies reveal a defined exchange bias obtained at the first annealing step and a decrease of total anisotropy field with partial crystallization after the subsequent annealing at 350 C.