The distinction between the magnetic properties of quasicrystalline and amorphous Al85-xPd15Mnx alloys

Abstract

Quasicrystalline and amorphous Al85-xPd15Mnx (x=12,13,14,15) alloys have been prepared by rapid melt quenching and high-rate DC sputtering. The saturation magnetic moment Ms, the magnetic Mn atom ratio, the magnetic moment per magnetic Mn atom Ps and spin glass behaviour have been investigated for both these phases. The temperature dependence of DC magnetic susceptibility for these quasicrystalline and amorphous alloys follows a Curie-Weiss law over a wide temperature range. The value of Ms and the average magnetic moment per Mn atom (Pc) for the quasicrystalline alloys are much smaller than those for the amorphous alloys. The magnetic Mn atom ratio in the quasicrystalline phase is about 10%, being almost half that in the amorphous phase in a similar manner to the Al80-xCu20Mnx (x=13, 14 and 15) alloy system. The Mn concentration dependence of Pc in the quasicrystalline phase is steeper than that in the amorphous phase, and the value of Pc of the quasicrystalline Al70Pd15Mn15 alloy exceeds 5 mu B of a bare moment of Mn. It is, therefore, considered that a giant moment is formed by polarization of 4d electrons of Pd in the quasicrystalline alloy. The present alloys in both phases are magnetically dilute alloys and spin glass behaviour has been observed. The spin freezing temperature Tf for the quasicrystalline phase is lower than those for the amorphous phase in accordance with the smaller Mn atom ratio. From these results, a marked difference in the magnetic properties between the quasicrystalline and amorphous phases has been confirmed, reflecting their different local atomic structure.