NEW INCOMMENSURATE PHASE IN K2ZNCL4 AT LOW-TEMPERATURE

The satellite reflections at (h+0.5, k+0.5, l) in K2ZnCl4 have been measured by neutron diffraction above and below the first-order phase transition at 144.5 K. In the intermediate phase between 144.5 K and 148.0 K, the satellite reflection at (2.5, 1.5, 0) splits into two peaks at (2.5±δ, 1.5, 0). This indicates that the intermediate phase is of an incommensurate structure which is characterized by the modulation wave number vector of q=(0.5±δ)a0* + 0.5b0*. The misfit parameter δ is about 0.04, and its temperature variation is slight. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.