The distribution of B-site in the perovskite for a d5-d3 superexchange system studied with Molecular field theory and Monte Carlo simulation

TL;DR

This study combines molecular field theory and Monte Carlo simulations to analyze B-site disorder in perovskites, providing a model that predicts lattice B-site distribution and explains phase transition behaviors in d5-d3 systems.

Contribution

The paper introduces a novel model for B-site distribution in perovskites applicable across doping levels, incorporating superexchange interactions and DM effects, advancing understanding of phase transitions.

Findings

The model accurately predicts B-site ordering for various compositions.

Long-range order emerges when x and y are large.

Distribution of Fe and Cr deviates from uniform, reducing Fe-Fe clustering.

Abstract

The B-site disorder in the d5 - d3 system of perovskites has been analyzed with molecular field theory and Monte Carlo method. The model is applicable to RFe1-pCrpO3 at any p value. When the saturation magnetization MS and phase transition temperature TP are known, a model can be built to calculate the order or disorder distribution of lattice B-sites. We analyze the case that the Fe-Cr superexchange is antiferromagnetic and ferromagnetic coupling respectively. The simulation result shows that the theoretical calculation formula is suitable for the calculation of different B-site distribution. Through the simulation, we find that when the x and y are large, the system will appear obvious long-range order. The DM interaction has a certain influence on the saturation magnetization. Via calculation, we found that the distribution states of Fe and Cr do not always conform to the uniform distribution but rather exhibit an effect that reduces the Fe-Fe clustering. The establishment of this model offers an explanation for several previously contentious issues, e.g., what is the phase transition temperature range of double perovskite, and why the different phase transition temperatures with the same doping proportion. It provides theoretical guidance for the design of functional materials with an arbitrary phase transition temperature.