Crystalline-field effects in the electron-spin resonance of rare earths in the noble metals

The effect of a low-lying crystalline-field excited state on the electron-spin-resonance (ESR) linewidth and g shift of the ground state in a dilute magnetic alloy is calculated. Departures from linearity are found for the linewidth at temperature substantially below the excitation energy of the first excited state. Measurements on Ag:Dy164 and (especially) Au:Er are reported which exhibit this behavior. Upon comparison with Ag:Gd and Ag:Er measurements, it is found possible to estimate the energy separation of the first excited level from the ground state from ESR linewidth and g-shift measurements alone.