MAGNETIC-ORDERING OF FE ATOMS IN ICOSAHEDRAL AL70-XBXPD30-YFEY QUASI-CRYSTALS

Novel icosahedral quasicrystals, in which Fe atoms possess a magnetic moment, have been found in Al70-xBxPd30-yFey compounds with 5<x<10 and 10<y<20. The compounds have ferromagnetic properties, and their Curie temperature ranges between 280 and 340 K, the saturation magnetizatio n sigma(S)(5 K)approximate to 7.5 emu/g. It follows from Mossbauer spe ctra that only a fraction of Fe atoms (12 to 15%) are magnetically ord ered at 4.2 K, and the mean saturation held [H-hf] = 96 kOe. The isome r shift values confirm that the atomic volume of magnetic Fe sites is larger than that of nonmagnetic Fe sites. The magnetic properties of t hese quasicrystals can be interpreted in terms of large magnetic clust ers with a size of 185 to 290 Angstrom. This size correspond to about 4x10(4) ''unit cells,'' hence the magnetic state can be described in t erms of bulk parameters. The localized magnetic moment of Fe atoms is tentatively ascribed to bonding between Fe and B, similarly to that in the amorphous Fesimilar to 50Bsimilar to 50 alloy. (C) 1997 American Institute of Physics.