Imaging Magnetic Frustration in Quasicrystal Artificial Spin Ices

Brajuskovic, Vuk

doi:https://doi.org/10.21985/n2-ym7f-h017

Work

Imaging Magnetic Frustration in Quasicrystal Artificial Spin Ices

Public

Download PDF

Download All Files (.zip)

The study of magnetic frustration has attracted considerable interest in the fields of materials science and condensed matter physics. Artificial Spin Ices (ASIs) are the primary systems in which magnetic frustration has been studied. To date, most studies on ASIs have been on fully periodic systems. In this thesis, we instead study quasicrystal (QC) ASIs based on a P2 Penrose tiling, which lack translational symmetry like periodic ASIs but have high rotational symmetry. This lack of translational symmetry results in novel forms of frustration as, while certain local structures are repeated, there is never an exact repetition of any one section of the lattice. In particular, we wish to understand how changes in the energy landscape of the QC-ASIs affects the resulting magnetization. By studying the global states of the QC-ASIs, we have found that they can be broken down into two sublattices. One sublattice consists of vertex motifs with a relatively low coordination number. The energy landscape of this sublattice is such that a change in the magnetization of one bar is more likely to result in a significant change in energy. The second sublattice consists of vertex motifs with a relatively high coordination number and its energy landscape is such that a change in the magnetization of bar is more likely to leave the overall energy relatively unchanged. The difference in the energy landscapes of these two sublattices leads to the formation of transient high energy states such as vortex states that form within the vertices of the QC-ASIs during magnetization reversal and magnetic solitons that become frozen in during cooling following a thermal anneal at the ordering temperature. The quasiperiodicity of the QC-ASIs also results in magnetization reversal in these ASIs proceeding through dendritic cascades rather the linear ones observed in traditional periodic ASIs.

Creator