FERROMAGNETIC-RESONANCE STUDIES OF ICOSAHEDRAL AL-MN-PD-B ALLOYS

Single-phase quasicrystalline alloys of the series Al70-xMn15Pd15Bx (0 less than or equal to x less than or equal to 10) prepared by the mel t spinning method have been shown to be of the icosahedral structure. Ferromagnetic resonance (FMR) studies have been undertaken in order to characterize the magnetic behaviour of these materials. The alloy wit h x = 0 exhibits a single resonance peak and does not exhibit spontane ous magnetic order. Alloys with x greater than or equal to 1 show the existence of two resonances due to two distinct Mn environments in the icosahedral structure. One resonance, resulting from non-magnetic Mn ions, shows FMR parameters which are temperature independent. The reso nance resulting from magnetically ordered Mn ions shows an amplitude a nd field which is a function of temperature, and disappears above a cr itical temperature. FMR measurements are supplemented with x-ray diffr action, calorimetry and magnetization data. The magnetic behaviour of this alloy system is explained on the basis of Anderson's theory of mo ment formation and the indirect coupling of 3d moments.