Chapter 5 Magnetism and quasicrystals

Abstract

Publisher Summary This chapter discusses the magnetism and quasicrystals (QCs). QCs are a new phase of condensed matter whose structures differ from those of either crystals or glasses. QCs exhibit long-range orientation order that is incompatible with three-dimensional periodic crystallographic packing. This non classical orientation order can only be accommodated in three dimensions by allowing for two sets of reciprocal lattice vectors of incommensurate length. Three-dimensional QCs are discovered thatexhibit five-fold symmetry (icosahedral QCs) and two-dimensional QCs with eight-fold (octahedral QCs) and ten-fold (decagonal QCs) orientational order are observed. However, other orientational orders are also possible. The important implications for crystal-field effects and moment formation on a local scale and for domain-wall symmetries on a long-range scale are reviewed in the chapter. New QC structures are metastable phases that are generally produced by rapid solidification or by some other nonequilibrium processing methods such as energetic particle-beam bombardment, solid-state reaction, and, in some cases, thermal transformation from an amorphous precursor, and mechanical alloying. The free energy of a given alloy composition decreases through a series of stable or metastable phases as the order increases from a short-range orientational order in amorphous metallic phases.