Exploring laser-induced interlayer spin transfer by an all-optical method

We investigate the influence of spin currents during ultrafast laser-induced demagnetization of magnetic bilayer structures by a new all-optical method to measure material- and/or depth-resolved magnetization dynamics. By describing the magneto-optical response of the bilayers in the complex Kerr plane, it is shown that the material-specific magnetization dynamics of the individual layers can be measured by a marginal adjustment to any conventional time-resolved magneto-optical Kerr effect setup. We use this technique to trace superdiffusive spin currents in magnetic Ni/Fe bilayers, providing new insight on its importance to ultrafast laser-induced demagnetization.