Annealing Effects on Magnetic Properties of Co/Pt Multilayers

Co/Pt multilayer films sputter-deposited with and without a substrate bias of V
_B
=-30 V were annealed in vacuum at 300 and 400°C. On annealing the saturation magnetization M
_s
and the saturation Kerr rotation angle θ
_K
both increased, while the perpendicular anisotropy energy K
_u
decreased monotonically. The decrease in K
_u
was larger for -30 V biased films than for 0 V films because of the larger decrease in the surface anisotropy K
_s
for -30 V biased films. This larger decrease in K
_s
is discussed taking the relaxation of lattice strain due to annealing into account.