ESR Observation of Coexistence of Paraelectric and Ferroelectric Phases in DKDP

Abstract

The ESR spectrum of SeO₄³⁻ radicals doped in the DKDP single crystal has been found to behave near T_c in a manner quite different from those of SeO₄³⁻ in KDP and Cr⁵⁺ in DKDP. The spectrum consists of two kinds of signals from paraelectric and ferroelectric phases of the crystal in a narrow temperature range around T_c. The range is estimated to be about 4 K. Above this range, only high symmetric paraelectric spectrum can be observed and the low symmetric ferroelectric one does not survive in contrast with the results on the KDP: SeO₄³⁻ and DKDP: Cr⁵⁺ previously reported.