Origin of Colossal Dielectric Response of Pr(0.6)Ca(0.4)MnO(3)

TL;DR

This study investigates the colossal dielectric response of Pr(0.6)Ca(0.4)MnO(3), revealing that the large dielectric constant primarily originates from Schottky barriers at contacts, with variations across samples and influence from magnetic fields.

Contribution

It demonstrates that the colossal dielectric constant in Pr(0.6)Ca(0.4)MnO(3) is mainly due to contact effects, providing a detailed analysis across multiple samples and conditions.

Findings

Dielectric constant varies from 1000 to 100000 across samples.

Large dielectric response is explained by surface barrier capacitance at contacts.

Magnetic field and bias measurements support contact-related origin.

Abstract

We report the detailed study of dielectric response of Pr(0.6)Ca(0.4)MnO(3) (PCMO), member of manganite family showing colossal magnetoresistance. Measurements have been performed on four polycrystalline samples and four single crystals, allowing us to compare and extract the essence of dielectric response in the material. High frequency dielectric function is found to be 30, as expected for the perovskite material. Dielectric relaxation is found in frequency window of 20Hz-1MHz at temperatures of 50-200K that yields to colossal low-frequency dielectric function, i.e. static dielectric constant. Static dielectric constant is always colossal, but varies considerably in different samples from 1000 until 100000. The measured data can be simulated very well by blocking (surface barrier) capacitance in series with sample resistance. This indicates that the large dielectric constant in PCMO arises from the Schottky barriers at electrical contacts. Measurements in magnetic field and with d.c. bias support this interpretation. Weak anomaly at the charge ordering temperature can also be attributed to interplay of sample and contact resistance. We comment our results in the framework of related studies by other groups.