Study of Neutron Double Refraction by Interferometry.

用LLL型完美晶体中子干涉仪对热中子的磁双折射现象进行了实验研究1)用一对永磁体磁化的高磁导率材料作为移相器，测量了完美晶体中子干涉仪输出的O-（透射）和H（衍射）中子束的强度变化。在相移器中，由于磁散射和核散射，干涉图的可见度和相位发生了明显的变化。实验结果与计算结果吻合较好。2)与1)中描述的相同的测量是使用完美的Fe-3%Si晶体进行的，其中没有任何磁场作为移相器施加。Fe-3%Si晶体内部用180个<s:1>磁畴壁划分，用中子形貌可以清晰地观察到其图像。从强度振荡分析中估计出晶体中铁原子的磁正向散射长度为5.56 × 10^<-8> cm，与已建立的值5.98 × 10^<-8> cm非常接近，这表明各畴的自发磁化几乎是饱和的。3)用赫斯勒合金晶体极化分析仪测量了双折射引起的中子极化变化。结果表明，在移相器的角度位置，干涉图样的可见性消失，出射中子束的偏振从-1到1周期性变化。这一现象可用于实现一种新型中子偏振器。

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.