An optical study of dislocation-induced anisotropy in alkali halide single crystals

Abstract

A series of investigations was carried out on four KCl single crystals and LiF single crystal to determine how the observed optical anisotropy of the samples was related to the magnetic anisotropy of alkali halide crystals detected by other experimenters. [Superscript 1,2,4,5] The birefringent crystals were subjected to a variety of tests, including magnetization and X-irradiation treatments, and the behavior of the anisotropy noted. Optical studies were made with the sample between crossed Nicol prisms using a sensitive photomultiplier detector. A majority of the optical-anisotropy-producing defects were linked with the <110> direction in the KCl crystal samples, in agreement with the direction of the defects that produced the magnetic anisotropy. Results of this investigation showed that the dislocations were responsible for the optical anisotropy, but that electrons along the dislocation lines, which are thought to be responsible for the magnetic anisotropy, did not contribute to the birefringence.