Hydrothermal synthesis of Bi2Fe4O9 nanochains and study of their multiferroic coupling

Abstract

We report synthesis of self-assembled Bi2Fe4O9 nanochains by hydrothermal method using Oleic acid as a surfactant which plays an important role in the self-assembled nanochain formation. Temperature dependent dc magnetization study suggests downward shift of the Neel temperature TN ~ 63 K for the particles of size ~ 22 nm while it is reported to be ~ 260 K in the bulk sample. The magnetic hysteresis (M−H) loops offer evidence of weak ferromagnetism across the entire temperature range 10–300 K. Exchange coupling across the interface between coexisting ferromagnetic and antiferromagnetic orders gives rise to a small amount of exchange bias at low temperature. The sample also exhibits substantial magnetoelectric multiferroic coupling at room temperature with ~77% suppression of ferroelectric polarization under 10 kOe magnetic field.