EVIDENCE FOR THE HIGH-TEMPERATURE SPIN-RELAXATION ANOMALY IN METAL-HYDRIDES

Proton spin-lattice relaxation data R1 (1/T1) are reported for the solid solution Nb0.5V0.5H0.36. In the region of the previously reported anomaly (T>700 K), a strong frequency dependence is observed by extending the measurements to a high frequency, 341 MHz. The correlation time tau(c) is determined and is found to decrease with increasing temperature. The mean-square magnetic-field fluctuation M2 responsible for the relaxation is also determined. Surprisingly, M2 increases rapidly with increasing temperature, suggesting an excited state with a large spin interaction, such as molecular hydrogen.