Magnetoplastic effect and spin-lattice relaxation in a dislocation-paramagnetic-center system

A magnetic induction threshold B-c above which the magnetoplastic effect - depinning of dislocations from paramagnetic pinning centers - can be observed in samples placed in a magnetic field is predicted and observed in Al, NaCl, and LiF crystals. The existence of a threshold is associated with the fact that for B<B-c the spin-lattice relaxation time tau(sl) in a dislocation-paramagnetic-center system is less than the time required for spin evolution in a magnetic field resulting in the removal of the spin forbiddenness of an electronic transition that ''switches off'' the dislocation-pinning-center interaction. It is shown that the threshold field B-c is sensitive to temperature and x-ray irradiation of the samples. A new method for measuring the spin-lattice relaxation time in paramagnetic centers on dislocations is proposed on the basis of the data obtained. (C) 1995 American Institute of Physics.