Order-disorder effects in the magneto-optical properties of evaporated Fe-Co alloy films

The magneto-optical properties of evaporated films of Fe-Co alloys have been studied as a function of composition using ellipsometric techniques to obtain the components of the index of refraction N = n-ik and the magneto-optical coefficient Q = Q 1 -iQ 2 at the He-Ne laser wavelengths of λ = 1.15μm and 0.63μm. The results indicate a very sharply defined compositional range between Fe .5 Co .5 and Fe .6 Co .4 in which the order-disorder transition affects the optical properties by increasing both n and k, as well as increasing |Q| to values larger than any previously reported except for the compound MnBi.