Annealing Effect on Internal Stress in Co/Pt Sputtered Multilayers

Co/Pt multilayer films were sputter-deposited onto glass substrates with a negative bias voltage applied during sputtering of either Co or Pt layers, and the perpendicular magnetic anisotropy and lattice strain were investigated in detail. An in-plane tensile stress was induced in the Co layers of films with zero bias voltage applied, while a compressive stress was found in biased films. The lattice strain was relaxed by annealing at 400°C in vacuum, resulting in a change in the volume anisotropy. In addition, the annealing causes interdiffusion of Co and Pt, thus decreasing the surface anisotropy energy.