Orientador: Carlos RettoriTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb WataghinResumo: Não informadoa Abstract: ESR experiments on diluted Er in Au and Ag and Dy in Ag thin films ( 300 Å - 5000 Å ) evaporated on NaCl and quartz substrates, were carried out at liquid helium temperatures. The anisotropy observed on the g - value, linewidth and lineshape were interpreted in terms of stress-induced admixtures of excited crystalline field levels with the G7 ground state, due to the difference in the thermal expansion coefficients between substrate and film. The data allows the estimation of lower limits for the tetragonal and trigonal second order spin-lattice coupling parameters. In Au their magnitude and sign agrees with that predicted by the point charge model, while in Ag the trigonal parameter does not. From the anisotropy of the g - value, linewidth and lineshape we were able to get some idea about the strain distribution across the filmDoutoradoFísicaDoutor em Ciencias