Dielectric and Elastic Studies of the Phase Transition in NaNH_4SeO_4・2H_2O

概要

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The dielectric constant of NaNH.Se0.? 2H.0 along the c axis under stress-free andclamped conditions, e$, and c5., were experimentally determined, and its elasticstiffnesses under constant electric field and constant electric polarization conditions,c'; and c:., and other elastic stiffnesses were also determined experimentally. It wasclarified that both e'Q. and 1 / c'; (.sp) follow the Curie-Weiss law, but the phase transi-lion in NaNH.SeO.- 2H.0 is caused by predominant dielectric instability more thanelastic instability. It was predicted basing on the Landau theory that one of threeelastic shear stiffnesses, c';, shows discontinuous behaviour at the Curie temperatureT., but the other two, c'; and c's, show continuous behaviours at T., if the phase Iransition is of first order. The prediction was confirmed to be the case by the experimental results.
社団法人日本物理学会の論文
1988-01-15