Strong temperature dependence of antiferromagnetic coupling in   CoFeB/Ru/CoFeB
  The temperature dependence of saturation and spin-flop fields for artificial ferrimagnets (AFi) based on antiparallel coupled CoFeB/Ru/CoFeB trilayers has been investigated in a temperature range between 80K and 600K. The results presented in this paper are relevant for magnetic devices using this system, e.g. magnetic-random access memory based on spin-flop switching. In good accordance to the theory, the saturation field Hsat behaves like Hsat ~ H_0 (T/T_0)/sinh(T/T_0) with a characteristic temperature of T_0 = 150K. Within this model, the Fermi velocity for the Ru layer is of the order of 10^5m/s, therefore, explaining the strong variation of the coupling strength with the temperature in Ru based AFi. Furthermore, a strong uniaxial anisotropy of K_u = 2x10^3 J/m^3 with a small angular distribution of the anisotropy axes is observed for the AFi trilayers based on amorphous CoFeB alloys. 
N. Wiese, T. Dimopoulos, M. R\"uhrig, J. Wecker, G. Reiss, J. Nogues,   J. Sort