Long-range Magnetic Order in Models for Rare Earth Quasicrystals

TL;DR

This paper investigates the magnetic properties of rare earth quasicrystals by modeling Ising spins with RKKY interactions on quasiperiodic tilings, revealing long-range magnetic order despite frustration.

Contribution

It introduces a two-step theoretical approach combining RKKY interaction calculations and Monte Carlo simulations to demonstrate long-range magnetic order in quasiperiodic systems.

Findings

RKKY interactions are frustrated and environment-dependent

Models exhibit a phase transition to long-range quasiperiodic magnetic order

Spin clusters can fluctuate below the ordering temperature

Abstract

We take a two-step theoretical approach to study magnetism of rare earth quasicrystals by considering Ising spins on quasiperiodic tilings, coupled via RKKY interactions. First, we compute RKKY interactions from a tight-binding Hamiltonian defined on the two-dimensional quasiperiodic tilings. We find that the magnetic interactions are frustrated and strongly dependent on the local environment. This results in the formation of clusters with strong bonds at certain patterns of the tilings that repeat quasiperiodically. Second, we examine the statistical mechanics of Ising spins with these RKKY interactions, using extensive Monte Carlo simulations. Although models that have frustrated interactions and lack translational invariance might be expected to display spin glass behaviour, we show that the spin system has a phase transition to low-temperature states with long-range quasiperiodic magnetic order. Additionally, we find that in some of the systems spin clusters can fluctuate much below the ordering temperature.