  Spin relaxation in the ultrathin metallic films of stacked microelectronic
devices is investigated on the basis of a modified Landau-Lifshitz equation of
micromagnetic dynamics in which the damping torque is treated as originating
from the coupling between precessing magnetization-vector and the introduced
stress-tensors of intrinsic and extrinsic magnetic anisotropy. Particular
attention is given to the time of exponential relaxation and ferromagnetic
resonance linewidth which are derived in analytic form from the equation of
magnetization energy loss and Gabor uncertainty relation between the
full-width-at-half-maximum in resonance-shaped line and lifetime of resonance
excitation. The potential of developed theory is briefly discussed in the
context of recent measurements.
