Signatures of long range dipolar interactions in artificial square ice

TL;DR

This study reveals that long-range dipolar interactions significantly influence the magnetic correlations in artificial square ice, challenging the assumption that only nearest-neighbor interactions are relevant.

Contribution

It demonstrates that including multiple further neighbor dipolar couplings is necessary to accurately model experimental magnetic structure factors in artificial square ice.

Findings

Long-range dipolar interactions affect magnetic correlations.

Multiple neighbor couplings are needed for semi-quantitative modeling.

Experimental features are only explained when extended interactions are considered.

Abstract

Analyzing the magnetic structure factor of a field demagnetized artificial square ice, qualitative deviations from what would predict the square ice model are observed. Combining micromagnetic and Monte Carlo simulations, we demonstrate that these deviations signal the presence of interactions between nanomagnets that extend beyond nearest neighbors. Including further neighbor, dipolar-like couplings in the square ice model, we find that the first seven or eight coupling strengths are needed to reproduce semi-quantitatively the main features of the magnetic structure factor measured experimentally. An alternative, more realistic numerical scenario is also proposed in which the ice condition is slightly detuned. In that case as well, the features evidenced in the experimental magnetic structure factor are only well-described when further neighbor couplings are taken into account. Our results show that long range dipolar interactions are not totally washed out in a field demagnetized artificial square ice, and cannot be neglected as they impact the magnetic correlations within or at the vicinity of the ice manifold.