Magnetized FeSi film with micrometer thickness inserted with Cr layers as π-flippers for neutron spin-echo spectrometry

Magnetized soft ferromagnetic films with micrometer thickness can be used as π-flippers for a spin echo small-angle neutron scattering (SESANS) instrument. Two FeSi monolayers and two FeSi/Cr multilayers were fabricated using a direct-current magnetron sputtering technique. The thicknesses of the two FeSi monolayers were 114 nm and 1140 nm, respectively. The two FeSi/Cr multilayers with 2 and 20 periods, respectively, were composed of FeSi layers having thicknesses of 1000 nm and 100 nm, respectively, and 10 nm-thick Cr layers. Hysteresis loop measurements and X-ray diffraction measurements were used to characterize their magnetic properties and texture, respectively. Polarized neutron flipping efficiency measurements were conducted using the TPNR (Time-of-flight and Polarized Neutron Reflectometer) to determine the flipping efficiency of the FeSi/Cr multilayer with [100 nm FeSi/10 nm Cr]20. The experimental results show that the saturation magnetization of the FeSi-monolayers decreased and the coercivity increased as their thickness increased. The FeSi/Cr multilayer with [100 nm FeSi/10 nm Cr]20 had higher saturation magnetization (1300 emu/cm 3) and lower coercivity than those of [1000 nm FeSi/10 nm Cr]2, although the total thickness of the FeSi layers was almost the same, and its maximum flipping efficiency was up to 98% for polarized neutrons.