By synchronizing a microwave waveform with the synchrotron x-ray pulses, we use the ferromagnetic resonance (FMR) of the Py (Ni81Fe19) layer in a Py/Cu/Cu75Mn25/Cu/Co multilayer to pump a pure spin current into the Cu75Mn25 spacer layer, and then directly probe the spin current in the Cu75Mn25 layer by a time-resolved x-ray magnetic circular dichroism (XMCD). This element-specific pump-probe measurement unambiguously identifies the AC spin current in the Cu75Mn25 layer. In addition, phase resolved x-ray measurements reveal a characteristic bipolar phase behavior of the Co spins that is a fingerprint of spin-current driven spin precession.
@article{arxiv.1505.03959,
title = {Direct detection of pure spin-current by x-ray pump-probe measurements},
author = {J. Li and L. R. Shelford and P. Shafer and A. Tan and J. X. Deng and P. S. Keatley and C. Hwang and E. Arenholz and G. van der Laan and R. J. Hicken and Z. Q. Qiu},
journal= {arXiv preprint arXiv:1505.03959},
year = {2016}
}