Theoretical basis for electro- and magnetoplasticity

The energy of dislocation bonds to paramagnetic obstacles depends on the spin multiplicity of the radical pairs formed by the orbitals of these entities. The radical pairs may be either in the singlet or in triplet spin states with strongly different binding energies. A magnetic field induces transitions between the singlet and triplet states. These transitions may result in an additional population of the triplet states with a lower binding energy than that of the singlet states. Depinning of the dislocations from obstacles is facilitated and, hence, the plasticity in a magnetic field increases. This mechanism allows one to explain the principal features of the magnetoplastic effect. The notions about spin-dependent transitions in the dislocation-obstacle systems were also used for an explanation of the nature of the electroplastic effect. We consider the electroplastic effect as a result of the magnetic field, induced by the electric current, acting on the dislocation depinning from paramagnetic obstacles. (C) 2000 Elsevier Science S.A. All rights reserved.