The Electron Spin Resonance Determination of Site Populations in Erbium Doped Calcium Fluoride.

摘要

The populations of erbium ions in the tetragonal, cubic, and trigonal sites in CaF2 crystals were measured for concentrations of .01 o/o, .03 o/o, .1 o/o, and .3 o/o erbium in CaF2 crystals. Experimental results show that the relative population of erbium ions in the cubic (quasi-cubic or perhaps aggregate) site increased as the concentration of total erbium ions increased while the relative site population in the tetragonal site decreased with increasing erbium ion concentration. The relative population in the trigonal site increased slightly from the .01 o/o to the .1 o/o concentration, then decreased in the .3 o/o concentration. Electron spin resonance techniques were used to obtain the absorption resonance characteristics of CaF2:Er(3+) in the different sites. The relative populations were determined as a function of total concentration of erbium ions. The doped crystals were maintained at liquid helium temperature (4.2K) and spin resonance spectra taken as a function of azimuthal angle of the DC magnetic field with respect to the (110) axis of the crystal in order to determine the symmetry and thus identify the site.