Transport properties in manganite thin films

TL;DR

This study investigates the temperature-dependent electrical resistivity of manganite thin films, revealing different scattering mechanisms and phase behaviors influenced by disorder and doping, with implications for understanding their transport properties.

Contribution

It provides a comprehensive analysis of resistivity in manganite thin films across various disorder levels and doping, supporting phase separation and magnon scattering theories.

Findings

Resistivity scales as T^{2.5} in low-temperature ferromagnetic phase with moderate disorder.

At high disorder, resistivity follows a T^{3} law indicative of anomalous magnon scattering.

In the high-temperature phase, resistivity exhibits activated behavior consistent with polaronic carriers.

Abstract

The resistivity of thin $La_{0.7}A_{0.3}MnO_{3}$ films ($A=Ca, Sr$) is investigated in a wide temperature range. The comparison of the resistivities is made among films grown by different techniques and on several substrates allowing to analyze samples with different amounts of disorder. In the low-temperature nearly half-metallic ferromagnetic state the prominent contribution to the resistivity scales as $T^{\alpha}$ with $\alpha \simeq 2.5$ for intermediate strengths of disorder supporting the theoretical proposal of single magnon scattering in presence of minority spin states localized by the disorder. For large values of disorder the low-temperature behavior of the resistivity is well described by the law $T^{3}$ characteristic of anomalous single magnon scattering processes, while in the regime of low disorder the $\alpha$ exponent tends to a value near 2. In the high temperature insulating paramagnetic phase the resistivity shows the activated behavior characteristic of polaronic carriers. Finally in the whole range of temperatures the experimental data are found to be consistent with a phase separation scenario also in films doped with strontium ($A=Sr$).