Development of ultra-slow muon instruments for spintronics studies under pulsed current conditions

パルス電流条件下のスピントロニクス研究に向けた超低速ミュオン実験装置開発

伊藤 孝   ; 髭本 亘  

Ito, Takashi; Higemoto, Wataru

The ultra-slow muon microscope (USMM) using a low energy tunable pulsed muon beam at J-PARC MUSE opens up new possibilities to investigate electromagnetic properties of thin films from a microscopic point of view in a depth-resolved manner. The depth resolution of this new apparatus (1 nm at the best) is much improved from that of the low-energy muon facility in PSI. This feature allows us to study nanoscale depth-dependent phenomena just below the surface. We plan to use USMM to investigate electric current-induced nonequilibrium spin accumulation in strong spin-orbit metals, which is expected to decay in nanometer length scale from their surface. In this presentation, we will report on the development of a mechanism for applying pulsed electric currents to metallic thin films at cryogenic temperatures, which are synchronized to 25-Hz muon pulses. A low duty factor of the pulsed currents 510 establishes both negligible Joule heating and high electric current density 10 A/m for a 50-nm thick Pt film. The pulsed current mechanism equipped on a He flow cryostat is compatible with the regulation on sample transfer for USMM.