iron arsenide formula is one of the main impurities in raw water in most sulfide ore mines and concentrates. It is also one of the major impurities in waste water from nonferrous metallurgical industrial processes. Iron arsenide is usually precipitated from aqueous solutions by coprecipitation with ferric hydroxide. The precipitate is subsequently subjected to filtration and electrowinning, which results in the production of high purity ferric arsenate. The purified product is used for the production of industrial grade iron and steel, as well as in the treatment of industrial wastewater.
The stability of superconductivity in iron arsenide at temperatures above Ts is a remarkable achievement. It reflects the robustness of the ordered structure of the FeAs slabs. However, it is still unclear what is the origin of this extraordinary phenomenon. It may be a result of the unique coupling between charge, spin, and phonons in the iron-pnictide system, which has so far been largely overlooked.
Recently, the anisotropy of conductivity in detwinned BaFe2As2 crystals was observed and attributed to the rotational symmetry breaking of the tetragonal phase by vibrational excitations associated with a spin-double exchange mechanism (16). However, a narrow absorption band with a singular polarization dependence emerges in a lower-energy region of the spectrum in which it is difficult to discern the contribution of a vibrational mode (17). This feature suggests that orbital degree of freedom plays a more important role than has been anticipated in the iron-pnictide system via unique coupling with charge, spin, and phonons.