Thermally and field-driven mobility of emergent magnetic charges in square artificial spin ice

TL;DR

This study investigates how emergent magnetic monopoles in artificial square spin ice respond to thermal and magnetic field stimuli, revealing a linear drift regime and temperature-dependent mobility characteristics.

Contribution

It introduces a detailed analysis of monopole mobility in artificial spin ice, incorporating a creep model and temperature effects, advancing understanding of magnetic charge dynamics.

Findings

Monopole drift velocity is linear in field above a critical threshold.

Monopole mobility increases with temperature and interaction strength.

Temperature-dependent critical field described by an extended Bean-Livingston model.

Abstract

Designing and constructing model systems that embody the statistical mechanics of frustration is now possible using nanotechnology. We have arranged nanomagnets on a two-dimensional square lattice to form an artificial spin ice, and studied its fractional excitations, emergent magnetic monopoles, and how they respond to a driving field using X-ray magnetic microscopy. We observe a regime in which the monopole drift velocity is linear in field above a critical field for the onset of motion. The temperature dependence of the critical field can be described by introducing an interaction term into the Bean-Livingston model of field-assisted barrier hopping. By analogy with electrical charge drift motion, we define and measure a monopole mobility that is larger both for higher temperatures and stronger interactions between nanomagnets. The mobility in this linear regime is described by a creep model of zero-dimensional charges moving within a network of quasi-one-dimensional objects.