Finite temperature ordering of dilute graphene antiferromagnets

TL;DR

This study uses large-scale quantum Monte Carlo simulations to investigate magnetic ordering in dilute graphene antiferromagnets, revealing a finite-temperature antiferromagnetic transition driven by long-range RKKY interactions.

Contribution

It provides the first detailed simulation-based analysis of magnetic ordering in dilute graphene systems with long-range interactions, highlighting a crossover in the ordering temperature's scaling behavior.

Findings

Finite-temperature antiferromagnetic order exists in dilute graphene with RKKY interactions.

The ordering temperature exhibits a crossover in its power-law scaling with dilution.

Long-range interactions induce a finite transition temperature in a two-dimensional system.

Abstract

We employ large-scale quantum Monte Carlo simulations to study the magnetic ordering transition among dilute magnetic moments randomly localized on the graphene honeycomb lattice, induced by long-ranged RKKY interactions at low charge carrier concentration. In this regime the effective exchange interactions are ferromagnetic within each sublattice, and antiferromagnetic between opposite sublattices, with an overall cubic decay of the interaction strength with the separation between the moments. We verify explicitly, that this commensurability leads to antiferromagnetic order among the magnetic moments below a finite transition temperature in this two-dimensional system. Furthermore, the ordering temperature shows a crossover in its power-law scaling with the moments' dilution from a low- to a high-concentration regime.