Local structure and ferromagnetic character of Fe-B and Fe-P amorphous alloys

We present clear experimental evidence that the dissimilar magnetic behavio r of Fe-B and Fe-P amorphous alloys is connected with differences in the lo cal structure around Fe atoms and with the different ferromagnetic characte r that these systems present. Structural parameters, obtained by x-ray abso rption fine structure, show that Fe-Fe nearest distances are responsible fo r the behavior of the Curie temperature. Both magnitudes increase with incr easing the metalloid content for Fe-B and remain constant for Fe-P. The res ults from x-ray magnetic circular dichroism reveal that Fe-B behaves as a w eak ferromagnet in all the composition range while Fe-P evolves from a weak to strong ferromagnetism character when P concentration increases. This fa ct determines the behavior of the magnetic moment with increasing metalloid content that displays a large decrease for Fe-P and a negligible variation for Fe-B.