Scaled frequency-dependent transport in the mesoscopically phase-separated colossal magnetoresistive manganite La_0.625-yPr_yCa_0.375MnO₃

Abstract

We address the issue of massive phase separation (PS) in the manganite family of doped Mott insulators through ac conductivity measurements on La_0.625-yPr_yCa_0.375MnO₃ (0.375 y 0.275), and establish the 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 the CO temperature. The impedance |Z(T,f)| measured over a frequency (f) range of 10 Hz-10 MHz in the critical regime follows a universal scaling of the form ≈R(T,0)g(fξ^2+θ), with θ≈0.86 and the normalized correlation length varying from 1 to 4, suggesting anomalous diffusion of holes in percolating FM clusters.