On thermalization of magnetic nano-arrays at fabrication

TL;DR

This paper presents a model predicting the thermalization process of magnetic nano-arrays during fabrication, highlighting how fabrication conditions influence the magnetic phases and effective temperature of the resulting artificial spin ice structures.

Contribution

It introduces a novel model linking fabrication parameters to the magnetic state and effective temperature of artificial spin ice, enabling control over phase access during growth.

Findings

Arrays can be described by an effective temperature.

Phase transitions depend on lattice constant and deposition temperature.

Control of effective temperature allows measurement of critical exponents.

Abstract

We propose a model to predict and control the statistical ensemble of magnetic degrees of freedom in Artificial Spin Ice (ASI) during thermalized adiabatic growth. We predict that as-grown arrays are controlled by the temperature at fabrication and by their lattice constant, and that they can be described by an effective temperature. If the geometry is conducive to a phase transition, then the lowest temperature phase is accessed in arrays of lattice constant smaller than a critical value, which depends on the temperature at deposition. Alternatively, for arrays of equal lattice constant, there is a temperature threshold at deposition and the lowest temperature phase is accessed for fabrication temperatures {\it larger rather than smaller} than this temperature threshold. Finally we show how to define and control the effective temperature of the as-grown array and how to measure critical exponents directly. We discuss the role of kinetics at the critical point, and applications to experiments, in particular to as-grown thermalized square ASI, and to magnetic monopole crystallization in as-grown honeycomb ASI.