Measurements of orbit-lattice coupling of Er and Dy impurities in Ag and Al hosts

The magnetic resonance of dilute Dy and Er impurities has been observed in thin polycrystalline Al and Ag films on two different substrates. The films are deposited at room temperature, and the measurements are made at liquid-helium temperatures. During cooling, the difference in thermal contraction between film and substrate produces an effectively uniaxial strain in the film. This results in an anisotropic $g$ value, which we have used to obtain lower limits on the orbit-lattice coupling coefficient for these systems. We find values for $V({\Gamma }_{3g}, 2)$ from 600 to 2000 ${\mathrm{cm}}^{-1\mathrm{}}$, somewhat smaller than observed in insulators, but of the same order of magnitude. Measurements on substrates with different thermal contractions indicate that all of the expected strain is present in these films, contrary to previous measurements on Ag: Er films grown on NaCl surfaces.