Dynamics of an octahedral Cu2+ jahn-teller system. consequences on its electron spin resonance

Publisher Website
Google Scholar
Abstract
The Cu2+(H2O)6 complex in zinc fluosilicate is subject to a « static » Jahn-Teller effect. It is well known that its spin resonance spectrum changes from one of tetragonal symmetry at low temperatures to become isotropic at high temperatures. We have made a detailed experimental study of this transition between 1.2 K and 80 K and compared the observations with the spectral features worked out from a model where the crystal vibrations cause the complex to reorient between the three strain stabilised tetragonal distortions. The model accounts very well for the observations without having to invoke excited levels. The reorientation rate 1/τ ~ 1.2 x 105 T3 s-1 was deduced from line broadening for 4.2 < T < 18 K and its extrapolation to higher temperatures confirmed by comparison with theoretically reconstructed spectra for H along < 100 > and < 111 > directions. The spin lattice relaxation time 1/T1 ~ 800 T3s-1 for 1.2 < T < 4.2 K. The « isotropic » spectrum shows a small trigonal anisotropy from which we estimate the parameters describing the trigonal component of the crystal field and calculate their effect in the low temperature region