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 400 °C annealed sample with MgO buffer increased by 10% form the 200 °C annealed sample (=0.73±0.01×10−11 J/m), while the exchange stiffness constant of without MgO buffer layer sample increase by 6% from the as-grown sample (=1.11±0.02×10−11 J/m).