Effect of Si interlayers on the magnetic and mechanical properties in Fe/Ge neutron polarizing multilayer mirror

Maruyama, Ryuji   ; Yamazaki, Dai   ; Okayasu, Satoru  ; Takeda, Masayasu  ; Zettsu, Nobuyuki*; Nagano, Mikinori*; Yamamura, Kazuya*; Hayashida, Hirotoshi; Soyama, Kazuhiko  

Neutron polarizing supermirrors need to display high polarization efficiencies at low external magnetic fields. The Fe/Si/Ge/Si multilayer, obtained by adding thin interlayers of Si to an Fe/Ge multilayer, is effective in reducing the external field strength necessary to achieve efficient neutron polarization. To gain insight into the mechanism that controls the required external field strength for a neutron polarizing supermirror, we investigated the magnetic and mechanical properties of Fe/Si, Fe/Ge, and Fe/Si/Ge/Si multilayers. The required external field strength was found to be proportional to the compressive film stress. The compressive stress of the Fe/Si/Ge/Si multilayer was much smaller than those of Fe/Si and Fe/Ge multilayers, respectively. These measurements and analyses showed that a reduction in the compressive film stress in the Fe/Si/Ge/Si multilayer permits the use of a lower external field strength to achieve efficient neutron polarization.