Competing soft dielectric phases and detailed balance in thin film manganites

Abstract

Using frequency dependent complex capacitance measurements on thin films of the mixed-valence manganite (La1−yPry)1−xCaxMnO3, we identify and resolve the individual dielectric responses of two competing dielectric phases. We characterize their competition over a large temperature range, revealing they are in dynamic competition both spatially and temporally. The phase competition is shown to be governed by the thermodynamic constraints imposed by detailed balance. The consequences of the detailed balance model strongly support the notion of an 'electronically soft' material in which continuous conversions between dielectric phases with comparable free energies occur on time scales that are long compared with electron-phonon scattering times.

Crossover of persistent photoconductivity in a phase-separated La0.325Pr0.3Ca0.375MnO3thin film

“…Upon cooling, the occurrence of the percolation transition at T P1 ≈ 92 K is clearly confirmed by the sharp changes in R as well as M. When the LPCMO was formed as a thin film, it lacked the COOI associated anomaly seen in bulk manganites [9,17]. Although the explicit signature of the COOI transition is absent in the R − T and M − T measurements of the LPCMO thin film, electron diffraction and complex capacitance measurements clearly show the onset of the COOI transition at about 210 K [18,19]. The accompanying large thermal hysteresis indicates phase separation of the FMM and COOI states and the first-order nature of the transition [14][15][16][17][18][19][20].…”

“…Although the explicit signature of the COOI transition is absent in the R − T and M − T measurements of the LPCMO thin film, electron diffraction and complex capacitance measurements clearly show the onset of the COOI transition at about 210 K [18,19]. The accompanying large thermal hysteresis indicates phase separation of the FMM and COOI states and the first-order nature of the transition [14][15][16][17][18][19][20]. The two hatched areas represent the 'PPC+' (80-110 K) and 'PPC−' (100-140 K) regions in the cooling and warming processes, respectively.…”