Fine Control of Multiferroic Features of Nanoscale BiFeO3 Powders Synthesized by Microwave-assisted Solid-State Reaction

다국어 초록 (Multilingual Abstract)

Variations in the multiferroic properties of BiFeO 3 (BFO) powders were investigated with respect to the crystallite size and Gd-doping. Nanoscale BFO powders with an average particle size range of ~ 30–80 nm were synthesized by a solid-state reaction using microwave-assisted heat treatment with Bi(NO 3 ) 3 ·5H 2 0, FeC 2 O 4 ·2H 2 O and Gd(NO 3 ) 3 ·6H 2 O as source precursors supplying Bi, Fe, and Gd, respectively. These were heat-treated at temperatures ranging from 200 to 700 °C. The reaction led to the formation of crystallite powders with a particle size of a few tens of nanometers. It was confi rmed that these samples had multiferroic properties at room temperature, and the value of M s varied signifi cantly from ferromagnetic to antiferromagnetic and vice versa with the size of the powders. In particular, ferromagnetic and ferroelectric features were observed when the size of the BFO powder was < ~ 30 nm (half of the spin-canted cycle). As the crystallite size was reduced to that corresponding to half of the spin canted cycle, the value of Ms increased by 8.8 times from 1.41 to 12.46 memu/g. Compared to pure BFO, when Gd was doped, Ms values increased by ~ 60% and 240% in ~ 30 nm and ~ 60 nm particle-sized powders.