Specific heat of NaNO2 near its transition points |
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Authors: | I Hatta A Ikushima |
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Institution: | Department of Physics, Faculty of Science, Tokyo Institute of Technology, Oh-okayama, Meguro-ku, Tokyo 152, Japan;The Institute for Solid State Physics, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan |
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Abstract: | Using an a.c. technique, the specific heat of NaNO2 was measured as a function of temperature near its antiferroelectric-to-paraelectric phase transition point (TN). The transition was found to be of the second order. The critical exponents are; α = 0·38 for ? = 2 × 10?4 ~ 1 × 10?1, and α′ = 0·18 for ? = ?2 × 10?4 ~ ?3 × 10?3. The critical exponents deduced from the scaling-law relations are roughly close to the values obtained from a random phase approximation for a system with an isotropic interaction. However, a difference was recognized between the observed exponent for the specific heat and the values theoretically given for T > TN by the random phase approximation for a system with a short-range interaction or for a system with a long-range dipolar interaction. A thermodynamical analysis was made by using the generalized Pippard relation, and the present result was found to be consistent with the pressure dependence of the antiferroelectric transition point. |
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