Anomalous 141Pr nuclear magnetic relaxation in PrF3 Van Vleck paramagnet

摘要

The magnetic nuclear spin-lattice relaxation has been studied in PrF3. It was found that 141Pr spin-lattice relaxation rate is untypically high for the Van Vleck insulator. According to all existing experimental data the only relaxation channel for enhanced nuclear moments at low temperatures is interaction with paramagnetic impurities and typical nuclear relaxation rate in rare earth Van Vleck paramagnets at liquid helium temperatures is 1 s?1. The measured value is 100 s?1. At the assumption that relaxation is caused by the strong 4f-4f cooperative interaction mediated by phonons [1], we measured 141Pr relaxation rates in a number of PrxLa1?xF3 samples and found that in diluted samples relaxation slows down to the usual for insulators values.