Magnetic Properties of the Highly Diluted Al-Fe Disordered System

Abstract

Disordered solid solutions containing a highly diluted magnetic element in which competitive exchange interactions are present, can allow the observation of different magnetic phases at dilutor element contents different from those corresponding to ordered alloys. In this work we present a simulational study of the magnetic properties of the Al-rich Al-Fe disordered alloy system, which meets the above mentioned requirements and it is, therefore, a good candidate to show differences between the magnetic phase diagrams corresponding to the ordered and disordered states. Our simulations were carried out on the basis of a random site-diluted Ising model, by using the Monte Carlo method as energy minimization tool. In our model, the Fe spins are assumed to be coupled by a nearest-neighbor ferromagnetic exchange interaction J (depending on the Al concentration); and by an Al-mediated antiferromagnetic superexchange interaction -αJ. Our results suggest the presence of ferromagnetic order for Al contents higher than those for which that order disappears in ordered alloys and the occurrence, for Al atomic percentages above 75% of a reentrant spin glass phase whose freezing temperature decreases with the degree of dilution.