THE MAGNETIC TRANSITION IN FE-SUBSTITUTED HEXAGONAL BETA-AL9SIMN3 PHASE

Recently we have studies β-Al9Si(Mn1-xFex)3 using Mössbauer effect spectroscopy with x=0.28 and discovered a new transition at about 80 K. Neutron diffraction studies down to low temperatures reveal no structural changes, so that this transition at 80 K is indeed of magnetic origin. The magnetic susceptibility shows a small maximum near this temperature superimposed on a large Curie-like background. In addition to this transition, the Curie-like background shows a cusp near 4 K. We thus infer a magnetic double transition in this disordered alloy. These magnetic transitions have been followed to lower Fe concentrations (x=0.10 and 0.20) by both Mössbauer spectroscopy (Tc) and by magnetic susceptibility (Tg). It is found that TC decreases rapidly with decreasing Fe concentration, while Tg remains relatively constant. The saturation hyperfine field Bhf(0) decreases rapidly with decreasing x, indicating that the Fe atoms loose their magnetic moments in the limit of infinite dilution, and the important role played by Fe-Fe nearest neighbors in determining the magnetic properties. © 1990 J.C. Baltzer A.G. Scientific Publishing Company.