  We study the charge and spin dependent scattering in a set of CoFeB thin
films whose crystalline order is systematically enhanced and controlled by
annealing at increasingly higher temperatures. Terahertz conductivity
measurements reveal that charge transport closely follows the development of
the crystalline phase, with increasing structural order leading to higher
conductivity. The terahertz-induced ultrafast demagnetization, driven by
spin-flip scattering mediated by the spin-orbit interaction, is measurable in
the pristine amorphous sample and much reduced in the sample with highest
crystalline order. Surprisingly, the largest demagnetization is observed at
intermediate annealing temperatures, where the enhancement in spin-flip
probability is not associated with an increased charge scattering. We are able
to correlate the demagnetization amplitude with the magnitude of the in-plane
magnetic anisotropy, which we characterize independently, suggesting a
magnetoresistance-like description of the phenomenon.
