Magnetic order and dynamics in Ammann-Beenker artificial magnetic quasicrystals

Artificial spin lattices (ASLs) consist of arrays of nanoscale magnets whose properties can be tuned by geometry and composition. Periodic ASLs, or artificial spin ices (ASIs), have been extensively studied as model systems for magnetic frustration (1, 2). ASIs are also emerging as platforms for unconventional computing (e.g., reservoir and neuromorphic) (3, 4). In contrast, understanding of aperiodic ASLs, artificial magnetic quasicrystals (AMQs), is limited. AMQs possess the aperiodicity of natural quasicrystals and can also exhibit complex magnetic order, frustration, and ground-state degeneracy. Here, we focus on the Ammann-Beenker AMQ (AB-AMQ), which is tiled using rhombi and squares (5). Thermally active AMQs were fabricated using permalloy (Ni_0.8Fe_0.2). Using photoemission electron microscopy (PEEM) imaging with x-ray magnetic circular dichroism (XMCD) as well as resonant x-ray scattering, we study the ground state ordering of the AB-AMQ and experimentally confirm the existence of degenerate ground states. Additionally, Monte Carlo simulations predict magnetic phase transitions in the AB-AMQ system. These dynamics were studied using temperature-dependent PEEM-XMCD and x-ray photon correlation spectroscopy.

1. Appl. Phys. Lett. 118, 110501 (2021).

2. Nat. Rev. Phys. 2, 13 (2020).

3. Nat. Nanotechnol. 17, 460 (2022).

4. Appl. Phys. Express 14, 033001 (2021).

5. J. Appl. Phys. 115, 17C502 (2014).