Deuteron Magnetic Resonance Study of Cupric Formate Tetrahydrate Cu(DCOO)_2・4D_2O

概要

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Deuteron magnetic resonance (DMR) of single crystals of Cu(DCOO)_2・4D_2O has been studied from 153°K to 291°K to reveal the changes in the structure and the motions of the crystalline water molecules due to the paraelectric-antiferroelectric phase transition (T_c=246.1±0.2°K). Above T_c, all the DMR lines of water molecules are broadened out by fast motions of deuterons among seven sites. Below T_c, 20 pairs of DMR lines are observed corresponding to four water molecules in stable position and two formate ions and their ac-plane enantiomorphs. Following conclusion are derived from measurements of temperature and angular dependences of the quadrupole splittings for these DMR lines. The phase transition is an order-disordering type of water molecules. In the antiferroelectric phase, the unit cell doubling occurs along the c-axis direction and the space group is P2_1/n. The structure involves a three dimensional ordering of water molecules. The structure of hydrogen-bond network is determined. Each two-dimensional layer of water molecules has a ferroelectric structure and the two successive layers in a unit cell arrange anti-parallel. Torsional motion of formate ion, DCOO-, is activated around the O…O direction.
社団法人日本物理学会の論文
1969-02-05