Nuclear spin-lattice relaxation times, T1, have been measured over a temperature range T=(1.1-300) °K and frequency range ν=2-15 MHz in a single crystal of CdS doped with 13-ppm cobalt. Minima in T1 vs T are observed, and absolute values of the effective electron relaxation time, τe, may be calculated at the temperatures of the minima, e.g., at 14 °K, τe=8.0×10-8 sec. At low temperatures, T≲5 °K, τe is dominated by a resonant Orbach process involving the two ground-state Kramers doublets (S=±3/2 and S=±1/2) which, according to our measurements, are split by Δ=(4±1) °K at zero magnetic field. At higher temperatures, T≳20 °K, τe is dominated by a nonresonant process, and these data are well fitted from 40 to 300 °K by τe-1∝T5J4(210/T), where J4 is a transport integral and 210 °K is the CdS Debye temperature.
Look, D. C.,
& Locker, D. R.
(1972). Nuclear-Magnetic-Resonance Study of Co2+ in CdS. Physical Review B, 6 (3), 713-718.