Study of Neutron Double Refraction by Interferometry.

用LLL型全晶体中子干涉仪进行了热中子磁双折射现象的实验研究。1）用一对永磁体磁化的高磁导率材料作为移相器，测量了全晶体中子干涉仪中O（透射）和H（衍射）中子束强度的变化。观察到移相器中磁散射和核散射引起的干涉条纹的振幅和相位的变化。实验结果与计算结果吻合较好。2）使用未施加任何磁场的完整Fe-3%Si晶体作为移相器进行了与1）中所述相同的测量。Fe-3%Si晶体内部被180 μ m的磁畴壁隔开，用中子形貌术可以清楚地观察到磁畴壁的图像。根据强度振荡的分析，晶体中Fe原子的磁前向散射长度估计为5.56 x 10^<-8>cm，这非常接近于已建立的值5.98 x 10^<-8>cm。这一结果表明，各畴的自发磁化强度几乎达到饱和。3）用Heusler合金晶体制成的极化分析仪测量了双折射引起的中子极化变化。结果表明，在干涉条纹消失的移相器角位置处，出射中子束的极化呈周期性变化，从-1到1。这一现象可能适用于实现一种新型的中子极化器。

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.