Effect of Chemical Pressure on the Magnetic Transition of Multiferroic Ca-BiFeO3

TL;DR

This study investigates how chemical doping with calcium influences the magnetic transition temperature of BiFeO3 ceramics, suggesting that chemical pressure can tune magnetic and ferroelectric properties to enhance magnetoelectric coupling.

Contribution

It demonstrates that calcium doping acts as chemical pressure, increasing the Neel temperature and providing insights into how hydrostatic pressure could similarly tune multiferroic properties.

Findings

Ca doping increases TNeel at 0.66K per 1%Ca

Chemical pressure effects suggest hydrostatic pressure can raise TNeel by ~2.2K/GPa

Pressure can potentially align ferroelectric and magnetic transition temperatures

Abstract

Multiferroic BiFeO3 ceramics have been doped with Ca. The smaller ionic size of Ca compared with Bi means that doping acts as a proxy for hydrostatic pressure, at a rate of 1%Ca=0.3GPa. It is also found that the magnetic Neel temperature (TNeel) increases as Ca concentration increases, at a rate of 0.66K per 1%Ca (molar). Based on the effect of chemical pressure on TNeel, we argue that applying hydrostatic pressure to pure BiFeO3 can be expected to increase its magnetic transition temperature at a rate around ~2.2K/GPa. The results also suggest that pressure (chemical or hydrostatic) could be used to bring the ferroelectric critical temperature, Tc, and the magnetic TNeel closer together, thereby enhancing magnetoelectric coupling, provided that electrical conductivity can be kept sufficiently low.