Element-resolved evidence of superdiffusive spin current arising from ultrafast demagnetization process
Rahul Gupta, F. Cosco, R. S. Malik, Xin Chen, Susmita Saha, A. Ghosh, T. Pohlmann, J. R. L. Mardegan, Sonia Francoual, R. Stefanuik, Johan Söderström, Biplab Sanyal, Olof Karis, Peter Svedlindh, Peter M. Oppeneer, Ronny Knut
Abstract
Using element-specific measurements of the ultrafast demagnetization of Ru/${\mathrm{Fe}}_{65}{\mathrm{Co}}_{35}$ hetero-structures, we show that Ru can exhibit a significant magnetic contrast (3% asymmetry) resulting from ultrafast spin currents emanating from the demagnetization process of the FeCo layer. We use this magnetic contrast to investigate how superdiffusive spin currents are affected by the doping of heavy elements in the FeCo layer. We find that the spin currents are strongly suppressed, and that the recovery process in Ru slows down by Re doping. This is in accordance with a change in interface reflectivity of spin currents as found by the superdiffusive spin transport model.