Scaled frequency-dependent transport in the mesoscopically phase-separated colossal magnetoresistive manganite La_{0.625-y}Pr_yCa_{0.375}MnO_3

TL;DR

This study investigates the frequency-dependent electrical transport in phase-separated manganite La_{0.625-y}Pr_yCa_{0.375}MnO_3, demonstrating the applicability of percolation scaling theory to understand its complex conduction behavior.

Contribution

It applies the scaling theory of percolation to ac conductivity measurements in manganite with phase separation, revealing universal behavior in the critical regime.

Findings

Impedance follows a universal scaling form in the critical regime.

Incomplete growth of ferromagnetic metallic phase observed on cooling.

Anomalous diffusion of holes in percolating FM clusters identified.

Abstract

We address the issue of massive phase separation (PS) in manganite family of doped Mott insulators through ac conductivity measurements on La$_{0.625-y}$Pr$_{y}$Ca$_{0.375}$MnO$_{3}$ (0.375 $\leq$ y $\leq$ 0.275), and establish applicability of the scaling theory of percolation in the critical regime of the PS. Measurements of dc resistivity, magnetization (M(T)) and electron diffraction show incomplete growth of a ferromagnetic (FM) metallic component on cooling the high temperature charge ordered (CO) phase well below Curie temperature. The impedance $\mid$Z(T,f)$\mid$ measured over a frequency (f) range of 10 Hz to 10 MHz in the critical regime follows a universal scaling of the form $\approx$ R(T,0)g(f$\xi^{2+\theta}$) with $\theta$ $\approx$ 0.86 and the normalized correlation length varying from 1 to 4, suggesting anomalous diffusion of holes in percolating FM clusters.