The pair exchange interactions and Jahn–Teller correlations of Cu(D2O)62+ centres in some Tutton salt crystals

Abstract

The pair exchange and vibronic interactions in the K2Zn0.92Cu0.08(SO4)2·6D2O (I) and (ND4)2Mg0.92Cu0.08(SO4)2·6D2O (II) single crystals were studied by the X-band EPR in the temperature range 4.2–300K. The pair of the similar (S–S) and dissimilar (D–S) Cu(D2O)62+ ions were recognised and characterised. All interactions were found to be ferromagnetic. The S–S exchange is about ten times stronger than D–S ones. The change of JS–S> in (I) from −0.026cm−1 at 4–20K to −0.047cm−1 above 110K was discovered. In (II) JS–S=−0.044cm−1 up to 110K and increases to −0.051cm−1 at 130K.The existence of the pair vibronic interactions was discovered in (I). The energy of the ferrodistortive correlations of 25cm−1 was found in (I) with energy interval between the two lowest Jahn–Teller configurations of the isolated ion equal to 72cm−1. The correlations in (II) are suggested to be antiferrodistortive.