Magnetoplastic effect in LiF crystals and longitudinal spin relaxation

New features of the dependence of the average travel distance l of dislocations on the magnetic field B have been found in an investigation of the magnetostimulated dislocation mobility in LiF crystals: A transition has been found from ordinary proportionality l∝B ² to saturation l≈ const in high fields B. It is shown that the experimental points can be described satisfactorily by the theoretical dependence l∝ (B ₀/B)²+1]⁻¹ (B ₀≈0.8 T), typical for the mechanism of longitudinal spin relaxation in a system of radical pairs, which are supposedly formed when dislocation nuclei interact with paramagnetic impurity centers. According to the theory, the level of the field B ₀ is determined by the characteristic frequency of the oscillations of the internal fields in the lattice, which for B ₀∼1 T is of the order of 10¹¹s⁻¹, which corresponds to the typical frequency of characteristic oscillations of dislocation segments between pinning centers, which, naturally, does not depend on temperature. This in turn explains the fact that the measured values of B ₀ are the same at 293 K and 77 K. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 749–753 (10 December 1999)