RELAXATION IN A JAHN-TELLER SYSTEM .I. COPPER IN OCTAHEDRAL WATER COORDINATION

A study has been made, using EPR and electron-spin-echo methods, on the Jahn-Teller systems La2Mg3(NO3)12•24H2O and its deuterated counterpart and Zn (BrO3)2•6H2O, all containing substitutional divalent copper. At low temperatures, it is found that the Cu2+•6H2O complex exists as a tetragonally distorted octahedron. Anisotropies in the g tensor or random strains may stabilize a distortion. Phonon-induced reorientation of the distortions is observed, using electron-spin-echo methods, and is found to yield a rate π-1 linearly dependent on temperature with a proportionality factor of 5×104 deg-1 sec-1 for La2Mg3(NO3)12•24D2O at temperatures up to 12°K. The spin-lattice relaxation rate T1-1 has been measured using the pulse-saturation method and is given by T1-1100T+3.3×10-2T5 for 1.3°K<T<20°K. Such a low-temperature rate is some four orders of magnitude faster than that observed for Cu2+ in the static octahedral water coordination of the KZn Tutton salt. Over the range that both have been measured, T1-1τ-1. © 1969 The American Physical Society.