Amorphous metallic alloys were developed at 1960. Since then, scientists have not stopped researching in order to improve their properties and find new applications. The innovation in techniques has let to the creation of functional structural materials with unknown properties until now, that have certain properties that could be of great utility for engineering applications. The aim of this project is to produce three amorphous steel alloys, Fe71.2-x C7.0Si3.3B5.5P8.7Cr2.3Al2.0Mox (x=0, 4.5 and 6.5 at%) by the melt-spinning technique. This work presents a detailed description of the basic equipment to produce these ribbons. The Fe-based metallic glasses were then characterized by electronic microscopy and X-ray diffraction that allow us to know the real composition of the ribbons and if the atomic structure is or is not amorphous. Transmission Mössbauer spectroscopy (TMS) allows us to study the local environments of the Fe atoms in the glassy state, showing the changes in the amorphous structure due to the addition of Mo. A reduction of the mean hyperfine field is observed as the amount of Mo increases. Moreover the three alloys were studied with differential scanning calorimetry (DSC) to find the glass transition temperature and to decide the suitable temperature of the heat treatments to relax the glasses. Finally, the relaxed samples were analized again with TMS in order to see the stability of the alloys and the effect of the local structure changes. The main conclusions reached during the project can be summarized as follows. In the alloys with intermediate Mo content, the hyperfine field reduction is associated to the substitution of Fe by Mo in a disordered magnetic Fe-rich structure, whereas for the alloys with high Mo content, this structure is destroyed leading to an increase of paramagnetic environments. The relationship between the GFA of these alloys and their local structure determined by TMS is discussed.