Electron spin resonance investigations of some fenoelectric sulphates

Abstract

The present ESR work on Cu²? in (NH?)?SO? is reportedly the first one on the Cu²? ion doped as an impurity in a trigonal bipyramidal environment in a diamagnetic host lattice. The present study shows that the symmetry of the crystal is lowered on going through the phase transition by the loss of the mirror plane perpendicular to the c?axis. It is also shown that hydrogen atom positions change in going through the phase transition, and this is consistent with the formation of stronger hydrogen bonds at low temperature as is already known from neutron diffraction studies. In this appendix it has been shown how in triplet species it is possible to see anomalous hfs in the fs components and how such a study helps in the determination of the sign of the zero?field splitting tensor. Further, it has also been pointed out here, for the first time, why in some circumstances this anomaly is not seen, and how this leads to certain inferences regarding spin?lattice interaction of the pair.