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

Variations in the multiferroic properties of BiFeO3 (BFO) powders were investigated with respect to the crystallite size and Gd-doping. Nanoscale BFO powders with an average particle size range of similar to 30-80 nm were synthesized by a solid-state reaction using microwave-assisted heat treatment with Bi(NO3)(3)center dot 5H(2)0, FeC2O4 center dot 2H(2)O and Gd(NO3)(3)center dot 6H(2)O as source precursors supplying Bi, Fe, and Gd, respectively. These were heat-treated at temperatures ranging from 200 to 700 degrees C. The reaction led to the formation of crystallite powders with a particle size of a few tens of nanometers. It was confirmed that these samples had multiferroic properties at room temperature, and the value of M-s varied significantly 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 < similar to 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 similar to 60% and 240% in similar to 30 nm and similar to 60 nm particle-sized powders. [Graphics] .