Magnetodielectric consequences of phase separation in the colossal magnetoresistance manganite Pr$_{0.7}$Ca$_{0.3}$MnO$_{3}$

We have studied the low-frequency dielectric properties of the phase-separated manganite Pr$_{0.7}$Ca$_{0.3}$MnO$_{3}$ as a function of applied magnetic field in the low temperature phase-separated state. The dielectric constant is strongly field dependent and also depends on the magnetic field history of the sample. The dielectric behavior appears to be associated with the hopping of polaronic charge carriers, and we can derive the field dependent hopping energy barrier from the frequency dependence of the dielectric constant. This analysis allows us to associate the metal-insulator transition observed in this material with the field-induced suppression of the polaron activation energy. Reference: \textit{Phys. Rev. B} \textbf{72}, 144429 (2005). Research was supported by the NSF and DOE.