Nuclear-Magnetic-Rosonance Study of Thulium Aluminum Garnet

The Tm"' and the Al" nuclear magnetic resonance have been studied in cubic thulium aluminum garnet. The Tm'6' results at 1.5'K give magnetic-susceptibility tensor components of x&=0.014, X2=0.551, and and X,=0.030 emu jg ion, which show much more anisotropy than found previously for thulium gallium garnet. The measured A12 paramagnetic shifts at 1.5 K agree quite well with values calculated from Tm'+-ion dipole sums, The Al" paramagnetic shifts from 1.5 to 300'K are used to calculate the approximate temperature dependence of the Tm'+-ion susceptibility components. The room-temperature A12' quadrupolar coupling constants ~ esqg/h ~ for the axially symmetric o and d sites are 0.892&0.005 and 6.155&0.005 MHz, respectively. The unshielded electric field gradients are calculated and compared with corresponding values for other aluminum garnets and for Fe" sites in several iron garnets. These field gradients agree quite well with values calculated using a point-charge model.