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The behavior with temperature variation of the “small-signal” dielectric constant of single crystals of SrTiO 3 has been measured from 296 down to 1.4°K, with a maximum value of 18,000 at 1.4°K. The temperature-dependence of the dielectric constant was observed to deviate from the classical Curie-Weiss law at ∼50°K. The D – E curves (“large-signal”) show a remnant or “spontaneous” polarization, and hence hysteresis, beginning at 45°K. A maximum value of the saturation polarization of 1.5 μC/cm2 was observed at 1.4°K. These data are taken as evidence of ferroelectricity in SrTiO 3 below 45°K.

Dielectric hysteresis in manganese dioxide has been studied in d.c. and a.c. fields as a function of temperature and the biassing field. At a temperature near 50°C., the dielectric constant is maximum and the loss factor tan δ is minimum. In the same temperature region, the saturation polarization, and the coercive field calculated from the hysteresis loop fall to a low value. These results give further indication of the ferroelectric properties of manganese dioxide.

The transverse force and flux distributions are examined for the important case of overlapping rectangular poles of saturable material. Results from measurements on physical devices and from numerical iterative solutions of the field equations are presented, with flux plots for varying pole positions. Accuracy, as determined from control cases and other means, is better than 1%. The transverse force is presented in a novel way as a unique function of the three variables, the mmf, the overlap distance, and the saturation polarization of the pole material. This shows that the force is remarkably independent of overlap, and for large overlap is double the force for the corresponding linear case and directly proportional to both the mmf and the saturation polarization.

The following paper deals with evidence of ferroelectricity in KNb${\mathrm{O}}_{3}$ and NaNb${\mathrm{O}}_{3}$. Temperatures at which both materials undergo crystallographic changes and corresponding changes in dielectric constant and loss tangent are reported. Photographs of dielectric hysteresis loops and values of saturation polarization taken at various points over a temperature range are given for KNb${\mathrm{O}}_{3}$.