Kinetics and thermodynamics of the degree of order of the B cations in double-perovskite Sr2FeMoO6

TL;DR

This study investigates how the ordering of B-site cations in Sr2FeMoO6 is influenced by kinetics and thermodynamics, showing that controlled synthesis conditions can significantly enhance magnetic properties.

Contribution

It introduces a low-O2-pressure encapsulation technique enabling long synthesis times to achieve high B-site cation order in Sr2FeMoO6.

Findings

High Ms values of 3.7-3.9 μB achieved at 1150°C with long heating periods

B-site cation order is controlled by both kinetics and thermodynamics depending on temperature

Special synthesis method prevents Mo evaporation, enabling equilibrium state attainment

Abstract

Here we show that the B-site cation (Fe/Mo) ordering in the double-perovskite magnetoresistor, Sr2FeMoO6, is controlled by either kinetics or thermal equilibrium depending on the temperature range. In order to enhance the ordering, long synthesis periods at moderate temperatures are thus required. Employment of a special oxygen-getter-controlled low-O2-pressure encapsulation technique for the sample synthesis enabled us to use long heating periods without evident evaporation of Mo, and thereby reach the thermal equilibrium state and a high degree of B-site cation order. For samples fired at 1150C for long periods (> 36 hours), record-high Ms values of 3.7 ~ 3.9 muB were obtained.