Magnetoplastic effect in LiF crystals and longitudinal spin relaxation

New features of the dependence of the average travel distance l of dislocat ions on the magnetic field B have been found in an investigation of the mag netostimulated dislocation mobility in LiF crystals: A transition has been found from ordinary proportionality l proportional to B-2 to saturation l a pproximate to const in high fields B. It is shown that the experimental poi nts can be described satisfactorily by the theoretical dependence l proport ional to[(B-0/B)(2) + 1](-1) (B-0 approximate to 0.8 T), typical for the me chanism of longitudinal spin relaxation in a system of radical pairs, which are supposedly formed when dislocation nuclei interact with paramagnetic i mpurity centers. According to the theory, the level of the field B-0 is det ermined by the characteristic frequency of the oscillations of the internal fields in the lattice, which for B-0 similar to 1 T is of the order of 10( 11) s(-1), which corresponds to the typical frequency of characteristic osc illations of dislocation segments between pinning centers, which, naturally , does not depend on temperature. This in turn explains the fact that the m easured values of B-0 are the same at 293 K and 77 K. (C) 1999 American Ins titute of Physics. [S0021-3640(99)00923-8].