Anisotropy of Nuclear Magnetic Resonance due to Crystal Dislocations

Abstract

Using plastically deformed crystals of KI, the nuclear magnetic resonance of I¹²⁷ has been observed. The broadened signals of I¹²⁷ show distinct anisotropy as regards the direction of the external magnetic field. This anisotropy is interpreted to arise from the definite orientation of a crystal dislocation. The experimental results are analyzed in terms of the gradient-elastic tensor which has been introduced by Shulman-Wyluda-Anderson. It is concluded that densities of edge and screw dislocations are fairly well balanced and increase for a certain range almost linearly with degree of cold-working, in agreement with the previously reported result for KBr. Assuming the total dislocation density to be 10⁹ cm⁻² for ten percent deformation, we get |C₄₄|∼8×10⁴ statvolts/dyne and its one-third for |C₁₁|. Comparison with the result for KBr shows that the amplification factor of eQq is greater than 50 for I¹²⁷ in KI.