Defect induced weak ferroelectricity and magnetism in cubic off-stoichiometric nano bismuth iron garnet: effect of milling duration

Abstract

The mechanical activation technique has been used to synthesize nanocrystalline multiferroic materials as it creates large density of crystal defects in these materials leading to novel magnetic properties of the nanostructured materials. In the present work, an attempt has been made to prepare nanocrystalline bismuth ferrite by mechanical activation process using high-energy planetary ball mill followed by sintering at 830 °C for 2 h. The milled powder was characterized using X-ray diffraction, scanning and transmission electron microscope, which revealed the formation of Bi_3−δFe₅O₁₂ instead of BiFeO₃. A giant dielectric peak has been observed at around the Curie temperature indicating magneto dielectric coupling which is a primary requisite for potential applications and transition temperature increases with the milling duration. Suppression in ferroelectric nature and enhancement in magnetic properties has been observed with the milling duration.