Superparamagnetism induced by polar nanoregions in relaxor ferroelectric (1$-$$x$)BiFeO$_{3}$-$x$BaTiO$_{3}$

TL;DR

This study discovers a new form of superparamagnetism in relaxor ferroelectric materials, where magnetic domains coincide with polar nanoregions, indicating strong coupling between electric and magnetic properties.

Contribution

The paper reveals that superparamagnetism in relaxor ferroelectrics is induced by polar nanoregions, establishing a direct link between magnetic domains and PNRs, which was not previously understood.

Findings

Magnetic particle size matches PNR size

Temperature-dependent domain sizes support the PNR-magnetism link

Strong electric-magnetic coupling via domain size is suggested

Abstract

A new class of superparamagnetism was found in relaxor ferroelectric 2/3BiFeO$_{3}$-1/3BaTiO$_{3}$. The size of the magnetic particle, estimated from the superparamagnetic magnetization curve, coincides with the size of the polar nanoregion (PNR), which governs the relaxor ferroelectric property. This suggests that the magnetic domain is identical to the PNR. The temperature variations in the sizes of the magnetic domains and PNRs estimated by our neutron diffraction measurements support this picture. Since the same domain provides both electric and magnetic properties, strong coupling between the two properties through the domain size is expected.