Spontaneous Liquid Crystal and Ferromagnetic Ordering of Colloidal Magnetic Nanoplates

TL;DR

This paper reports a novel colloidal suspension of magnetic nanoplates that spontaneously forms a ferromagnetic liquid crystal phase, exhibiting unique magnetic textures and high sensitivity to magnetic fields without external alignment.

Contribution

It introduces a new spontaneous ferromagnetic liquid crystal phase of magnetic nanoplates, demonstrating zero-field magnetization and self-organized magnetic textures.

Findings

Spontaneous ferromagnetic liquid crystal formation

Distinctive magnetic self-interaction effects

High sensitivity to Earth's magnetic field

Abstract

Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles are randomly oriented but their moments become aligned if a magnetic field is applied, producing a variety of exotic and useful magneto-mechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in absence of a field. Here we report a fluid suspension of magnetic nanoplates which spontaneously aligns into an equilibrium nematic liquid crystal phase that is also macroscopically ferromagnetic. Its zero-field magnetization produces distinctive magnetic self-interaction effects, including liquid crystal textures of fluid block domains arranged in closed flux loops, and makes this phase highly sensitive, with it dramatically changing shape even in the Earth's magnetic field.