Wide bandwidth neutron polarizing supermirror due to ferromagnetic interlayer exchange coupling

丸山 龍治; 山崎 大; 青木 裕之; 阿久津 和宏*; 花島 隆泰*; 宮田 登*; 曽山 和彦; Bigault, T.*; Saerbeck, T.*; Courtois, P.*

no journal, , 

The polarized neutron off-specular scattering measurement of Fe/Ge periodic multilayers revealed that the ferromagnetic (FM) interlayer exchange coupling between neighboring Fe layers grew with decreasing Ge thickness less than 2 nm. The FM interlayer exchange coupling observed here contributed to the presence of the saturation magnetization comparable to the bulk and to smaller coercivity and larger initial permeability than the multilayer without the FM interlayer exchange coupling. This offers a possibility to keep the spontaneous magnetization for the multilayer with a thin bilayer thickness and hence to increase the bandwidth of the polarizing supermirror. We proposed a modified layer sequence of the neutron polarizing supermirror, where the minimum Fe thickness was set to 3.5 nm, whereas the Ge thickness was reduced. A performance test of the neutron polarizing supermirror showed that the FM interlayer exchange coupling contributed to the presence of the magnetization comparable to the bulk and resulted in a marked enhancement in the m-value larger than 6.