Study of Neutron Double Refraction by Interferometry.

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Experiments on magnetic double refraction phenomena of thermal neutrons were made using a perfect crystal neutron interferometer of LLL type1) The variation of intensities of O-(transmitted) and H(diffracted) neutron beams from a perfect crystal neutron interferometer was measured using high permeability materials magnetized by a pair of permanent magnets as phase shifters. Changes of visibilities and phases of interference pattern, which were due to magnetic and nuclear scattering in phase shifters, were clearly observed. The agreement between experimental results and calculated ones was well.2) The same measurement as described in 1) was made using a perfect Fe-3%Si crystal to which any magnetic field was not applied as a phase shifter. The inside of the Fe-3%Si crystal was partitioned with 180ﾟ magnetic domain walls whose images were clearly observed by neutron topography. From the analysis of intensity oscillations the magnetic forward scattering length of Fe atoms in the crystal was estimated as 5.56 x 10^<-8> cm, which is very close to the established value, 5.98 x 10^<-8> cm. This result indicates that the spontaneous magnetization in each domain is almost saturated.3) The change of polarization of neutrons caused by double refraction was measured by a polarization analyzer made of a Heusler alloy crystal. The result indicates that at the angular position of the phase shifter where the visibility of interference pattern vanished, the polarization of outgoing neutron beam changed periodically from -1 to 1. This phenomenon may be applicable to the realization of a new kind of neutron polarizer.