Novel measurement of hyperfine interactions in solids: 207Pb3+ in YPO4 and LuPO4

Stable trivalent lead impurities have been observed at room temperature in ''flux-grown'' single crystals of YPO/sub 4/ and LuPO/sub 4/ by electron paramagnetic resonance. Because of a fortuitous set of circumstances, a unique measurement of the hyperfine constant of /sup 207/Pb/sup 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 /sup 31/P neighbors has also been measured and, surprisingly, this interaction is larger for the second /sup 31/P neighbors than for the first /sup 31/P neighbors.