HIGH-PRESSURE FORMS OF CSNIF3

The atmospheric pressure form of CsNiF3 consists of hcp layers of CsF3 with F6 octahedra face-shared to form infinite chains along the c axis. CsNiF3 transforms at ∼5 kbars to a 9-layer stacking sequence with 2/3 of the layers hcp and 1/3 of the layers ccp while at ∼50 kbars it transforms to a 6-layer stacking sequence with 1/3 of the layers hcp and 2/3 of the layers ccp. Once formed, these phases are stable at atmospheric pressure to several hundred degrees C. The 9-layer phase is paramagnetic above 80°K with μeff=3.2 μB and θp=-75°K. Trace amounts of a ferromagnetic material prevented further analysis below 80°K. The light-yellow 6-layer phase shows a ferrimagnetic Tc=111°K and a dTc/dp=0.53°K/kbar. The magnetic and optical properties are very similar to the isostructural RbNiF3. © 1969 The American Institute of Physics.