Room temperature magnetoelectric coupling in single crystal Bi₂Fe₄O₉ nanotubes grown within an anodic aluminum oxide template

Abstract

Single crystalline Bi₂Fe₄O₉ nanotubes with diameter ~ 100 nm were synthesized within the pores of Anodic Aluminium Oxide template by vacuum injection technique. The material showed ferroelectric hysteresis and weak ferromagnetism. The latter is ascribed to uncompensated spin at the nanotube surface. A core shell structure with an antiferromagnetic core and a ferromagnetic shell explain the observation of an exchange bias in the specimen. The latter showed a 20% relative change in the dielectric constant for an applied magnetic field of 1.9 Tesla. This is ascribed to a change in the non centro-symmetricity of the crystal due to magnetostriction.