Competition between ferromagnetic and charge-orbital ordered phases in Pr$_{1-x}$Ca$_{x}$MnO$_3$ for $x$=1/4, 3/8, and 1/2

TL;DR

This study investigates the competition between ferromagnetic and charge-orbital ordered phases in doped manganites, revealing a small energy difference that explains the colossal-magnetoresistive effect observed experimentally.

Contribution

The paper combines analytic mean-field and numerical techniques to model spin, charge, and orbital structures, providing new insights into phase competition in manganites at specific doping levels.

Findings

Small energy difference between FM and COO phases at studied densities.

Theoretical predictions align with experimental spin-charge-orbital patterns.

Results support the robustness of colossal-magnetoresistive effects across a range of densities.

Abstract

Spin, charge, and orbital structures in models for doped manganites are studied by a combination of analytic mean-field and numerical relaxation techniques. At realistic values for the electron-phonon and antiferromagnetic $t_{2g}$ spin couplings, a competition between a ferromagnetic (FM) phase and a charge-orbital ordered (COO) insulating state is found for $x$=1/4, 3/8, and 1/2, as experimentally observed in Pr$_{1-x}$Ca$_{x}$MnO$_3$ for $x$=0.3$\sim$0.5. The theoretical predictions for the spin-charge-orbital ordering pattern are compared with experiments. The FM-COO energy difference is surprisingly small for the densities studied, result compatible with the presence of a robust colossal-magnetoresistive effect in Pr$_{1-x}$Ca$_{x}$MnO$_3$ in a large density interval.