Ground states of a family of frustrated spin models for quasicrystals and their approximants

TL;DR

This paper investigates the ground states of cluster spin models to understand magnetic order in quasicrystals and approximants, revealing two novel quasiperiodic magnetic phases.

Contribution

It introduces analytically tractable spin models that capture key features of quasicrystals and approximants, identifying new magnetic phases.

Findings

Identification of two novel quasiperiodic magnetic phases.

Models reproduce experimental signatures of magnetic order and spin glass behavior.

Results motivate further numerical studies of magnetic ordering in quasicrystals.

Abstract

Many new families of quasicrystal-forming magnetic alloys have been synthesized and studied in recent years. For small changes of composition, the alloys can go from quasiperiodic to periodic (approximant crystals) while conserving most of the local atomic environments. Experiments show that many of the periodic approximants order at low temperatures, with clear signatures of ferromagnetic or antiferromagnetic transitions, and also in some cases undergo non-equilibrium spin glass transitions. In contrast, the quasicrystals are mostly found to be spin glasses. Systematically studying these alloys could help elucidate the role played by quasiperiodicity in (de)stabilizing long range magnetic order. In this work, we study cluster spin models with the aim of understanding the mechanisms behind various types of long range magnetic ordering in approximants and quasicrystals. These models embody key features of real systems, and to some extent are analytically tractable, both for periodic and quasiperiodic cases. For the quasicrystal, we describe two novel magnetic phases with quasiperiodic ordering. Our results should serve to motivate further studies with detailed numerical explorations of this family of models.