Magnetism in Al(Si)-Mn quasicrystals and related phases.

An extreme sensitivity of the magnetic properties to the atomic structure has been observed in Al(Si)-Mn and Al-Pd-Mn quasicrystals, approximants, and liquids with similar Mn concentrations (of the order of 8%- 20%). Here, we show that the effect of the local environment of the Mn atoms is not sufficient to explain this complex behavior. A new model is presented, which, taking into account Mn-Mn interactions mediated by the conduction electrons over large distances ( 5 A and more), allows one to understand why only a small fraction of the Mn atoms carry a localized magnetic moment in quasicrystals and why a large proportion is magnetic in liquids.