Optical Properties Of Ba(Fe1-Xtmx)(2)As-2 (Tm = Cr, Mn, And Co)

In this chapter, I report the optical conductivity spectra of magnetic impurity substituted Ba(Fe $$_{1-x}$$ TM $$_{x}$$ ) $$_2$$ As $$_2$$ (TM = Cr and Mn) and compare them with that of nonmagnetic impurity substituted Ba(Fe $$_{1-x}$$ Co $$_{x}$$ ) $$_2$$ As $$_2$$ . I found that the coherent charge transport is strongly suppressed by magnetic impurities, such as Cr and Mn. In addition, the magnetic-impurity-substitution induces a novel spectral feature related to the carrier localization in the far-infrared region above the antiferromagnetic transition temperature. I attribute the behavior to the cooperative effect between conduction electrons and local magnetic order induced by magnetic impurities. The present results demonstrate that Cr and Mn are not conventional magnetic pair-breakers in iron pnictides.