FORMATION OF THE SODIUM 1-D STRUCTURES IN DOPED NACL BY HIGH-ENERGY ELECTRON-IRRADIATION

An investigation of the formation and properties of linear sodium stru ctures in electron-irradiated potassium doped NaCl crystals was carrie d out by means of electron spin resonance (ESR) and nuclear magnetic r esonance (NMR). It has been found that the behavior of ESR and NMR sig nals depends on the dose and temperature. The most interesting propert ies were observed in heavily irradiated samples. The magnetic spin sus ceptibility determined by ESR signal intensity showed temperature inse nsitive Pauli paramagnetism at high temperature and then decreased bel ow 160 K, indicating metal-insulator transition (MIT). The nuclear spi n-lattice relaxation rate T-1(-1) showed a remarkable (root) frequency dependence, which is due to the one-dimensional diffusive motion of e lectrons. The influence of some impurities on the formation of microst ructures has been studied too and the nature of the MIT at low tempera tures in heavily irradiated NaCl:K crystals is discussed. (C) 1998 Els evier Science Ltd. All rights reserved.