ULTRAFAST SPIN DYNAMICS IN NICKEL

The spin dynamics in Ni is studied by an exact diagonalization method on the ultrafast time scale. It is shown that the femtosecond relaxati on of the magneto-optical response results from exchange interaction a nd spin-orbit coupling. Each of the two mechanisms affects the relaxat ion process differently. We find that the intrinsic spin dynamics occu rs during about 10 fs while extrinsic effects such as laser-pulse dura tion and spectral width can slow down the observed dynamics considerab ly. Thus, our theory indicates that there is still room to accelerate the spin dynamics in experiments.