Spin-Lattice Relaxation of Al^{27} in Thulium Aluminum Garnet

Abstract

The Al27 spin-lattice relaxation time T1 has been measured between 127 and 425 °K at 8 and 14 MHz for the aluminum a and d sites in thulium aluminum garnet. Both sites exhibit T1 dips at 275 °K which are attributed to Al27-Tm169 cross relaxation. Below 190 °K the a-site T1 magnitudes and approximately ω−2 frequency dependence are explained by magnetic field fluctuations caused by the Tm3+ ion making transitions between its two lowest crystal-field levels with a correlation time near 4 × 10−12 sec.