Optimization of the Gilbert Damping Constant by Annealing CoFeB Films Sandwiched by Ta, Ru, and Pd Layers

The effects of annealing on the Gilbert damping constant and the magnetic properties are investigated in CoFeB films sandwiched by either Ta, Ru, or Pd layers. As the annealing temperature increases, the damping constant is found to be slightly decreased first and then, rapidly increased. The minimum damping constant is, thus, obtained with a 300 °C-annealed Ta/CoFeB/Ta film while the samples with Ru and Pd layers exhibit their minimum at 200 °C. The coercive field also exhibits a behavior similar to the damping constant; thus, an empirical correlation between them is proposed.