Multiferroic order in BiFeO₃ nanoparticles

Multiferroics exhibit simultaneous presence of magnetic and electric ordering. The archetypical multiferroic material, BiFeO₃ (BFO), has attracted much attention since it has both, high ferroelectric Curie temperature (1103 K) and, high antiferromagnetic Néel temperature (643 K) in bulk and thin film form. Furthermore, it has one of the highest electrical polarization (~90μC/cm2) among ferroelectric materials. We propose a new route to a magnetic control via nano-structuration in the form of nanoparticles (NPs). We have grown BFO NPs by a sol-gel process and found that their magnetism can be tuned from antiferromagnetic to ferromagnetic by controlling the particle size. Piezoelectric force microscopy and VSM measurements show that our NPs are ferroelectric and ferromagnetic, and therefore our results open new ways to achieve magnetoelectric coupling in BFO nano-structures.