Magnetic properties of icosahedral Al-Pd-Mn quasicrystals

The magnetic properties of icosahedral Al-Pd-Mn phases have been investigated by studying a large set of samples, including single crystals and polycrystalline ribbons. The composition and structure (F, F 2 , or F 2 M ) of each sample have been determined. Composition changes and thermal treatments lead to a wide range of magnetic susceptibility variations (by a factor around 55). The comparison of susceptibility data for all studied samples, as well as for literature samples, shows that the temperature dependence of the magnetic susceptibility exhibits a universal behavior, whatever the structural state, composition, and thermal treatment. It can be accounted for by a Kondo effect gradually affected by magnetic RKKY-type interactions as the concentration of magnetic Mn atoms increases. The magnetic Mn atom concentration is small, ranging from 3.8×10 - 5 for the less magnetic sample studied up to 2×10 - 3 for the more magnetic one-i.e., much less than the Mn concentration in the icosahredral phase(∼8×10 - 2 ). It varies with thermal treatments and depends strongly on the composition of the icosahedral phase. In particular, the magnetic properties are found to evolve along the growth direction of a large single grain obtained by the Czochralski technique in relation with composition variations.