Spin Dynamics of Rare Earth Ions in Phosphate Laser Glasses

The spin dynamics of rare earth ions (Er, Nd, Sm and Gd) in heavily doped phosphate glasses have been investigated using 31P NMR. Correlation times in the range 10^-2 to 10^-12 s have been obtained for temperatures between 4 K and 100 K. No evidence of spin-spin coupling between the ions has been found and spin relaxation occurs via conventional phonon processes, including the Orbach process. A model involving inhomogeneous broadening of the NMR resonance lines, with distinct sample regions corresponding to the presence or absence of nuclear spin diffusion, has been used in extracting the electron spin correlation times from the NMR measurements.