Direct Detection of Pure ac Spin Current by X-Ray Pump-Probe Measurements

J Li; L R Shelford; P Shafer; A Tan; J X Deng; P S Keatley; C Hwang; E Arenholz; G van der Laan; R J Hicken; Z Q Qiu

doi:10.1103/PhysRevLett.117.076602

Direct Detection of Pure ac Spin Current by X-Ray Pump-Probe Measurements

Phys Rev Lett. 2016 Aug 12;117(7):076602. doi: 10.1103/PhysRevLett.117.076602. Epub 2016 Aug 11.

Authors

J Li^{1

2}, L R Shelford³, P Shafer⁴, A Tan², J X Deng², P S Keatley³, C Hwang⁵, E Arenholz⁴, G van der Laan⁶, R J Hicken³, Z Q Qiu²

Affiliations

¹ International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
² Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA.
³ Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, Devon EX4 4QL, United Kingdom.
⁴ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
⁵ Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, Republic of Korea.
⁶ Magnetic Spectroscopy Group, Diamond Light Source, Didcot, Oxfordshire OX11 0DE, United Kingdom.

PMID: 27563981
DOI: 10.1103/PhysRevLett.117.076602

Abstract

Despite 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.