Effect of annealing temperature on exchange stiffness of CoFeB thin films

We investigate the exchange stiffness constants of 28-nm-thick CoFeB film using Brillouin light scattering. Series of CoFeB films are prepared on the MgO(001) substrate with or without additional 5-nm thick MgO buffer layer, the effect of the annealing temperature on the exchange stiffness constants are studied. We found that the exchange stiffness constant of 400oC annealed sample with MgO buffer increased by 10 % form the 200oC annealed sample (=0.73 +/- 0.01 x 10-11 J/m), while the exchange stiffness constant of without MgO buffer layer sample increase by 6 % from the as-grown sample (=1.11 +/- 0.02 x 10-11 J/m).