X-Ray Diffraction Study on the Incommensurate-Commensurate Phase Transitions in {N(CH₃)₄}₂CoCl₄

抄録

By means of X-ray diffraction study two incommensurate phases were found in {N(CH₃)₄}₂CoCl₄ in the temperature ranges of 20.6∼8.0°C and 6.3∼4.5°C. As the temperature decreases, the modulation wave vector q₀ decreases from about 0.42c^* at 20°C to the commensurate value of 2⁄5c^* without a recognizable jump at 8.0°C. Between 8.0 and 6.3°C, it stays at 2⁄5c^* and below 6.3°C it decreases from 2⁄5c^* to about 0.39c^* at 4.5°C and then jumps to the commensurate value of 1⁄3c^*. Between 4.5 and −81°C (monoclinic phase) it stays at 1⁄3c^*.