Electron spin relaxation of the Jahn–Teller Cu(H2O)6 complex in Cs2Zn(SO4)2·6H2O crystals

The electron spin–lattice and phase relaxation times were measured by electron spin echo (ESE) method in the temperature range 10–50K, where Jahn–Teller dynamics of the Cu(H2O)6 complexes is too slow to dominate in the EPR spectra of Cu2+ in Cs2Zn(SO4)2·6H2O. The spin–lattice relaxation is governed by ordinary the two-phonon Raman processes which overdominate the effects expected from the Jahn–Teller dynamics. It allowed us to determine the Debye temperature of Cs2Zn(SO4)2·6H2O crystals as ΘD=220K. The ESE amplitude decay is governed by nuclear spectral diffusion below 23K with phase memory time TM=5μs. At this temperature a broadening of the lines in FT-ESE spectrum (pseudo-ENDOR spectrum) appears, and then a continuous acceleration of the phase relaxation on heating is observed. This is due to the excitations to the vibronic level of energy 71cm−1 in the deepest well of the potential energy surface.