Study of optical properties and electronic structure of ferromagnetic FeCo

The optical properties of ordered cubic FeCo were investigated by spectroscopic ellipsometry in the 1.5–5.5 eV photon energy region at room temperature. A strong absorption structure exists around 2 eV in the optical conductivity spectrum of the compound, which is located close to that of pure bcc Fe. The spin-polarized band structure of FeCo calculated by the linear-muffin-tin orbitals method shows that the d-states from Co sites disperse in the same energy region as those from Fe sites. The calculated real part of the optical conductivity of FeCo from its band structure exhibits a strong absorption structure around 2 eV in good agreement with the experimental spectrum. Such agreement indicates a dispersive character of the d-bands of FeCo comparable to those of pure Fe.