Double Hysteresis Loop of BaTiO3 at the Curie Point

Walter J. Merz
Phys. Rev. 91, 513 – Published 1 August 1953

Abstract

It is known that the Curie point θ of the ferroelectric BaTiO3 shifts to higher temperatures when a dc bias field is applied. If the crystal shows a sharp transition, we expect by applying an ac field at the Curie temperature that the crystal would become alternately ferroelectric and nonferroelectric in the cycle of the ac field. This can be seen in the shape of the hysteresis loop at temperatures slightly above θ. In the center of the polarization P versus field E plot, we observe a linear behavior corresponding to the paraelectric state of BaTiO3 above θ. At both high voltage ends, however, we observe a hysteresis loop corresponding to the ferroelectric state. A change in temperature causes a change in size and shape of the double hysteresis loops, ranging from a line with curves at the ends (higher temperature) to two overlapping loops (lower temperature). The results obtained allow us to calculate the different constants in the free-energy expression of Devonshire and Slater. One of the results shows that the transition is of the first order since the P4 term turns out to be negative. The properties of the hysteresis loops are discussed, especially the large spontaneous electrical polarization and the low coercive field strength.

  • Received 23 April 1953

DOI:https://doi.org/10.1103/PhysRev.91.513

©1953 American Physical Society

Authors & Affiliations

Walter J. Merz

  • Bell Telephone Laboratories, Murray Hill, New Jersey

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Vol. 91, Iss. 3 — August 1953

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