Artificial square ice and related dipolar nanoarrays

TL;DR

This paper investigates artificial square ice dipolar nanoarrays, analyzing their thermodynamics, dynamics, and phase transitions, and explores how geometric modifications influence their magnetic states and ordering behaviors.

Contribution

It introduces models for the thermodynamics and dynamics of lithographically fabricated dipolar arrays, showing how to stabilize ice regimes and induce different magnetic states.

Findings

Ice regime stabilization via geometric adjustments

Identification of a thermodynamic ordering transition

Detection of a dynamical bottleneck preventing full equilibration

Abstract

We study a frustrated dipolar array recently manufactured lithographically by Wang {\em et al.} [Nature {\bf 439}, 303 (2006)] in order to realize the square ice model in an artificial structure. We discuss models for thermodynamics and dynamics of this system. We show that an ice regime can be stabilized by small changes in the array geometry; a different magnetic state, kagome ice, can similarly be constructed. At low temperatures, the square ice regime is terminated by a thermodynamic ordering transition, which can be chosen to be ferro- or antiferromagnetic. We show that the arrays do not fully equilibrate experimentally, and identify a likely dynamical bottleneck.