Influence of a weak magnetic field on spin-dependent relaxation of structural defects in diamagnetic crystals

The purpose of the work is to investigate relaxation of residual stresses a nd metastable point defects and plastic properties of ionic crystals in cro ssed static and microwave magnetic fields at the paramagnetic resonance con dition. It is revealed that coincidence of quantum energy of a microwave fi eld with energy of Zeeman splitting of electronic spin sublevels of paramag netic centers leads to an increase in relaxation rate of residual stresses and of metastable point defects, and, as a result, to resonant weakening of crystals which manifests itself in an increase of dislocation mobility and macroplastic flow rate, as well as in a decrease of crystal microhardness. It is shown that the metastable Ca and Eu aggregates sensitive to a static magnetic field in the absence of microwave fields are responsible for reso nant weakening. The resonance arises in short-lived non-thermalized states of these aggregates excited by thermal fluctuations. (C) 2000 Elsevier Scie nce S.A. All rights reserved.