Polymorphic nanowires of magnetic shape memory MnAs

TL;DR

This paper explores how strain in nanostructured MnAs influences its crystal phases and magnetic properties, revealing a new stable phase in nanowires that could impact future magnetic and electronic device applications.

Contribution

It demonstrates, through first-principles calculations, the existence of a new stable crystal phase in MnAs nanowires induced by strain and one-dimensional confinement, extending understanding of shape memory nanostructures.

Findings

MnAs nanowires as small as two nanometers can be stable in a new crystal phase.

Strain from surfaces induces structural transitions in MnAs nanowires.

The structural transition involves twin domains and could be applicable to other magnetic nanowire systems.

Abstract

For nanostructured materials, strain is of fundamental importance in stabilizing a specific crystallographic phase, modifying electronic properties, and in consequence their magnetism when it applies. Here we describe a magnetic shape memory alloy in which nanostructure confinement strain influences the crystallographic phase and the electronic and magnetic properties of the resulting nanowires. We use first-principles calculations on shape memory MnAs nanostructures to study the influence of strain on crystal phases, which arises from surfaces. We show that MnAs nanowires down to two nanometers can be stable in a new crystal phase different from bulk hexagonal and induced by one-dimensionality. The changes between structures through use of strain require the existence of twin domains. Our analysis suggests that the strain-induced structural transition, demonstrated here in MnAs compounds, could be extended to other (magnetic) shape memory nanowire systems for applications ranging from mechanical to magneto-electronic devices.