DETERMINATION OF HOST-ION SPIN-LATTICE RELAXATION-TIMES FROM GD3+ EPR LINEWIDTHS IN NH4PR(SO4)2.4H2O, NH4SM(SO4)2.4H2O, NH4CE(SO4)2.4H2O, NH4ND(SO4)2.4H2O SINGLE-CRYSTALS

Spin-lattice relaxation times (τ) for the host rare-earth ions R3+ (R Sm, Ce, Nd) in NH4R(SO4)2·4H2O crystal lattices have been estimated at room-temperature from X-band EPR linewidths of Gd3+ impurity ion, using an appropriate expression based on the second moment for crystals consisting of two different kinds of paramagnetic spins. In addition, the τ values for Pr3+ ions in NH4Pr(SO4)2·4H2O lattice have been estimated in the 266-410 K temperature range from EPR linewidths of the impurity ion Gd3+. The values of τ for Pr3+ indicate that τ-1 varies as T7 (T = temperature) in the 266-296 K range, and as T2 in the range 296-410 K. It is concluded that the T7 behaviour is predominantly due to the sum process, while the T2 behaviour is predominantly due to the Raman process. © 1990.