Debye-H\"uckel theory for spin ice at low temperature

TL;DR

This paper applies Debye-Hückel theory to low-temperature spin ice, modeling magnetic monopoles as a Coulomb liquid, and compares theoretical predictions with experimental and numerical data.

Contribution

It provides a detailed, context-specific Debye-Hückel framework for understanding magnetic monopoles in spin ice at low temperatures, including thermodynamics and dynamics.

Findings

Debye-Hückel theory accurately describes specific heat and AC susceptibility data.

Entropic Coulomb interactions are negligible in current compounds.

Derived an expression for monopole mobility considering bound pairs.

Abstract

At low temperatures, spin ice is populated by a finite density of magnetic monopoles-pointlike topological defects with a mutual magnetic Coulomb interaction. We discuss the properties of the resulting magnetic Coulomb liquid in the framework of Debye H\"{u}ckel theory, for which we provide a detailed context-specific account. We discuss both thermodynamical and dynamical signatures, and compare Debye H\"{u}ckel theory to experiment as well as numerics, including data for specific heat and AC susceptibility. We also evaluate the entropic Coulomb interaction which is present in addition to the magnetic one and show that it is quantitatively unimportant in the current compounds. Finally, we address the role of bound monopole anti-monopole pairs and derive an expression for the monopole mobility.