Studies on dielectric relaxation in ceramic multiferroic Gd_1−xY_xMnO₃

Abstract

Dielectric study over a broadband was carried out from 10 to 70 K on ceramic Gd1−xYxMnO3 (x=0.2, 0.3 and 0.4). For all the compositions, a prominent sharp peak about ~18 K was observed in the temperature dependence of both ε′(T) and ε″(T) at all frequencies, indicating a long‐range ferroelectric (FE) transition. Using Cole‐Cole fit to the permittivity data, the relaxation time τ and the dielectric strength ∆ε were estimated. Temperature variation of τ(T) in the Arrhenius representation is found to be nonlinear (non‐Debyean relaxation), with increasing barrier‐activation energy over successive temperature‐windows. Interestingly, for all the compositions, we witness a jump in τ(T) about the ferroelectric transition temperature, concurred by a broad‐maximum in ∆ε(T),signifying the critical slow down of relaxations near long‐range FE‐correlations.

Strain-Engineered Tetragonal Phase and Ferroelectricity in GdMnO3 Thin Films Grown on SrTiO3 (001)

“…In addition, the observed anomalies in the imaginary part of ɛ ”(T) are also frequency dependent in the whole studied temperature range. These features in ε ’(T) and ε ”(T) evidence for the existence of a dielectric relaxation process in GMO thin film, whose activation energy is 80 meV, higher than the reported value 22 meV found in bulk GMO 25 . The ɛ ”(T) curve measured at 1 kHz exhibits a small anomaly at 105 K, which is associated with the antiferrodistortive phase transition of the STO substrate.…”