Novel Measurement of Hyperfine Interactions in Solids:Pb+3207in YPO4and LuPO4

Stable trivalent lead impurities have been observed at room temperature in "flux-grown" single crystals of YP${\mathrm{O}}_4$ and LuP${\mathrm{O}}_4$ by electron paramagnetic resonance. Because of a fortuitous set of circumstances, a unique measurement of the hyperfine constant of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}_{}^{3+}{}_{}{}^{}$ in these materials was possible. The resulting values are the largest ever observed for the trivalent lead ion in a solid. A super hyperfine interaction with ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ neighbors has also been measured and, surprisingly, this interaction is larger for the second ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ neighbors than for the first ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ neighbors.