Raman process studied by 87Rb spin-lattice relaxation in a Rb2ZnCl4 single crystal at low temperature

87Rb 1/2↔−1/2 spin-lattice relaxation time in the Rb2ZnCl4 single crystal was measured in the temperature range of 4.2–300 K. The dominant relaxation of this crystal in the whole temperature range investigated here is due to quadrupolar interaction. The changes in the 87Rb spin-lattice relaxation rate near 75 and 192 K correspond to the phase transitions in the crystal. These suggest that the phase IV to III transition is of second-order, and the phase III to II transition is of first-order. The temperature dependence of the relaxation rates in phases II, III, and IV is in accordance with the Raman process dominated by the phonon mechanism.