Structural modifications induced by electronic energy deposition during the slowing down of heavy ions in matter

Abstract

The defects or the phase transformations induced by high density electronic excitation are studied in thick targets. Two kinds of materials have been studied: electrical conductors and magnetic insulators. These materials are insensitive to individual electronic excitations such as those created by photon or electron irradiations. In amorphous metallic alloys a two step process of damage creation has been observed: defect production followed by a change of dimensions of the samples. In high- T c. superconductors large electronic excitations enhance the rate of decrease of the critical temperature except in La 2CuO 4 where T c increases upon ion irradiation. In the case of magnetic insulators a description of ion-induced tracks is proposed which accounts for the experimental data over the whole range of electronic energy losses. Two rates of damage, correlated with a change of the shape of induced defects, are shown by Mössbauer spectroscopy and high resolution electron microscopy observations.