Dynamic origin of segment magnetization reversal in thin-film Penrose tilings

摘要

Artificial quasicrystals (AQC) have become the subject of a new research effort in the area of magnetic metamaterials for magnonic applications. Fibonacci lattices or quasicrystal tilings occupy a unique niche of "intermediate order" lying in between periodic crystals and amorphous materials: they are aperiodic, but "locally" self-similar. Two-dimensional Penrose P2 tilings (P2T), in particular, can be built up by consecutive iterations of a "deflation" algorithm to yield a finite network of wire segments having two lengths, d_1 and d_2, with global fivefold rotational symmetry, but without translational symmetry. Elongated thin-film segments are connected to outline the characteristic P2 tiling of "kites" and "darts" (see supplemental material in). The strong segment shape anisotropy forces the segment magnetizations to be parallel or antiparallel to their long axis in weak external magnetic fields. For this reason, the segments are often termed, "Ising macrospins". The global P2T rotational symmetry is broken by the application of an external magnetic field. The segment magnetization aligns as much as possible with an increasing field until the field is strong enough to overcome the segment shape anisotropy and destroy the Ising macrospin.