Verification of ultrafast spin transfer effects in iron-nickel alloys
Christina Möller, Henrike Probst, G. S. Matthijs Jansen, Maren Schumacher, Mariana Brede, J. K. Dewhurst, Marcel Reutzel, Daniel Steil, Sangeeta Sharma, Stefan Mathias
Abstract
Abstract The optical intersite spin transfer (OISTR) effect was recently verified in Fe 50 Ni 50 using extreme ultraviolet magneto-optical Kerr measurements. However, one of the main experimental signatures analyzed in this work, namely a magnetic moment increase at a specific energy in Ni, was subsequently found also in pure Ni, where no transfer from one element to another is possible. Hence, it is a much-discussed issue whether OISTR in FeNi alloys is real and whether it can be verified experimentally or not. Here, we present a comparative study of spin transfer in Fe 50 Ni 50 , Fe 19 Ni 81 and pure Ni. We conclusively show that an increase in the magneto-optical signal is indeed insufficient to verify OISTR. However, we also show how an extended data analysis overcomes this problem and allows to unambiguously identify spin transfer effects. Concomitantly, our work solves the long-standing riddle about the origin of delayed demagnetization behavior of Ni in FeNi alloys.