Tunable morphology and magnetic properties of Bi ₂Fe ₄O ₉ nanocrystal synthesized by hydrothermal method

Bi ₂Fe ₄O ₉ nano and micron powders have been synthesized by a hydrothermal method. The as-obtained samples are pure phase and crystallize in the orthorhombic structure. Diverse particle morphologies, including nanoplates, nanospheres, microcubes, and microcylinders, are obtained under different synthesis conditions. The solvent N, N-Dimethylformamide (DMF), together with the mineralisers NaOH and NH ₄OH, are found to be the key factors for the formation of the particles with their diverse morphologies and sizes. The magnetization dependence of temperature (M-T), observed in a field of 1000 Oe from 10 to 340 K, and M-H loops measured at 10 K indicate that the Bi ₂Fe ₄O ₉ particles are paramagnetic at room temperature and undergo an antiferromagnetic transition at a Néel temperature (T _N) of 250 K.