“…Additionally, concerning the application, it is important to say that Bi 2 Fe 4 O 9 compound is an important material that can be used for a semiconductor gas sensor and catalyst for ammonia oxidation to NO [5,6]. This compound shows a para-antiferromagnetic transition around 240-265 K [3,7], in which the magnetic ordering is due to superexchange interaction between the Fe ions mediated by the O atoms.…”