PublishedThis is the author accepted manuscript. The final version is available from American Physical Society via the DOI in this record.There is another ORE record for this article: http://hdl.handle.net/10871/22513Despite recent progress in spin-current research, the detection of spin current has mostly remained indirect. By synchronizing a microwave waveform with synchrotron x-ray pulses, we use the ferromagnetic resonance of the Py (Ni_{81}Fe_{19}) layer in a Py/Cu/Cu_{75}Mn_{25}/Cu/Co multilayer to pump a pure ac spin current into the Cu_{75}Mn_{25} and Co layers, and then directly probe the spin current within the Cu_{75}Mn_{25} layer and the spin dynamics of the Co layer by x-ray magnetic circular dichroism. This element-resolved pump-probe measurement unambiguously identifies the ac spin current in the Cu_{75}Mn_{25} layer.We acknowledge helpful discussion with Arne Brataas.
Financial support from the National Science Foundation
Grant No. DMR-1504568, Future Materials Discovery
Program through the National Research Foundation of
Korea (Grant No. 2015M3D1A1070467), and Science
Research Center Program through the National Research
Foundation of Korea (Grant No. 2015R1A5A1009962) is
gratefully acknowledged. The Advanced Light Source is
supported by the U.S. Department of Energy under Award
No. DE-AC02-05CH11231. J. D. acknowledges fellowship
support from the China Scholarship Council and National
Science Foundation of China under Grant No. 51331006.
L. R. S., P. S. K., and R. J. H. acknowledge the support of
the Engineering and Physical Sciences Research Council
(EPSRC) through Grants No. EP/J018767/1 and No. EP/
I038470/1. G. v. d. L. acknowledges support of the EPSRC
through Grant No. EP/J018767/1
