Dielectric Anomalies of NaN0_2 above the Ferroelectric Curie Tomperature

概要

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The physical properties of NaN0_2 above the ferroelectric Curie temperature have drawn many worker's interest since Tanisaki^<1)> discovered a microdomain structure existing immediately above the Curie temperature. Hoshino and Shibuya^<2),3)> showed from their precise X-ray measurements that there are at least two anomalies above the Curie temperature. First one exists about 1℃ above the Curie temperature and corresponds to thed isappearance of a peculiar stmcture in which the magnitude of spontaneous polarization of (100) net plane is sinusoidally modulated along the <100> direction. They also discovered a small λ-type anomaly on specific heat vs. temperature curve at this temperature^<4)>. Second one exists at about 15℃above the Curie temperature and is characterized by an anomaly in lattice dilatation^<2)>. The cause of this anomaly is not clear but may probably be some kind of short range order or antiferroelectric cluster which may disappear around tbis point. At these points, anomalies in the dielectric properties should be expected. Already, Sawada et al.^<5)> reported a gradual change in the slope of the ε^<-1> vs. T curve at about 15℃ above the Curie temperature. A careful control of the temperature of the specimen must be necessary in order to decide whether this change is gradual or abrupt.
社団法人日本物理学会の論文
1964-01-05