Extraordinary Tunability of the Superexchange Interactions in Nanoparticles of the Multiferroic 0.50BiFeO3-0.50PbTiO3

TL;DR

This study demonstrates that in 0.50BiFeO3-0.50PbTiO3 nanoparticles, the superexchange interactions can be significantly tuned, raising the Ne9el temperature from 120K to 350K by adjusting ferroelectric distortions, enabling room-temperature multiferroic applications.

Contribution

It reveals a novel size-dependent enhancement of antiferromagnetic superexchange interactions in multiferroic nanoparticles, unlike non-multiferroic oxides.

Findings

Ne9el temperature increases from 120K to 350K with size reduction

Superexchange interactions are tunable via ferroelectric distortion

Potential for room-temperature multiferroic device development

Abstract

The coexistence and coupling of magnetic and ferroelectric orderings in single phase multiferroics has evinced enormous scientific interest as it involves breaking of time reversal and space inversion symmetries in the same material. The mutual controllability of the two diverse orderings in multiferroics has potential for developing new generation multifunctional sensor, actuator and data storage devices. We present here evidence for a new exotic facet of multiferroicity, whereby one can raise the strength of antiferromagnetic (AFM) superexchange interaction and hence tune the N\'eel temperature (TN) from ~120K in bulk to ~350K in 18nm size particles by tuning the ferroelectric distortion in the tetragonal phase of multiferroic (1-x)BiFeO3 -xPbTiO3 solid solutions . This observation is unique to multiferroics only as the TN in non-multiferroic AFM oxides decreases with particle size. Our results provide a scientific basis for designing room temperature single phase multiferroics, useful for making multifunctional device operating at room temperature.