¹⁴NNMR investigation of KSCN

¹ J. Stefan Institute, SI-1000 Ljubljana, Slovenia
² Institut für Experimentalphysik, Universität Wien A-1090, Wien, Austria
³ Department of Physics, University of Utah, Salt Lake City, Utah 84112

Received: 9 April 1997
Accepted: 12 August 1997

Abstract

We have directly determined with  NMR the SCN head-tail flipping rate in KSCN on going through the order-disorder phase transition at T_c. The results can be explained in terms of an asymmetric double-well potential for the SCN reorientations below T_c and a symmetric double-well potential above T_c. The time scale for the SCN fluctuations is so slow that low symmetry angular rotation patterns are observed in the high-temperature high-symmetry phase. KSCN thus seems to be the first known example where a structural phase transition can be observed with NMR in the slow-motion and not in the fast-motion regime and where a dynamic breaking of the symmetry of the high-temperature phase takes place.