Optical and magneto-optical properties of Fe 4−x Co x (x=1–3)

We report a systematic study of the electronic, optical, and magneto-optical properties of the Fe4-xCox (x = 1–3) compounds using the full-potential linearized augmented plane waves (FPLAPW) method within the local spin density approximation (LSDA). Pure Fe (x = 0) and Co (x = 4) have also been studied, the latter in hcp as well as bcc structure, to offer a better comparison. A good agreement is obtained between calculated optical conductivity spectra and experimental data. We note that the magneto-optical properties of these compounds are found to be more akin to those of bcc Co (which has MOKE very similar to that of bcc Fe) than to those of hcp Co. This shows strong impact of the environment on the MOKE of these compounds. With respect to the elemental values, the magnetic moments at Fe sites are found to be larger in general, while those at Co sites are almost the same. However, interestingly, despite their larger magnetic moment, the Kerr rotation remains comparable to that of bcc Fe for most of the energy range. The origin of Kerr spectra has been explained in terms of optical transitions