Spontaneous liquid crystal and ferromagnetic ordering of colloidal magnetic nanoplates

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 magnetomechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in the absence of a field. Here we report a fluid suspension of magnetic nanoplates that 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.

A comparison between size dependent paraelectric and ferroelectric BaTiO3 nanoparticle doped nematic and ferroelectric liquid crystals

“…This is often achieved by coating the surface with monomolecular organic materials, surfactants (stabiliser), or ligands. For instance, oleic acid, 7,10,17,20,21,[24][25][26][27] selenium docosane 28 and dodecylbenzenesulphonic acid 29,30 have been widely utilized for the coating of NPs.…”

Gold Nanoparticles Thin Films with Thermo‐ and Photoresponsive Plasmonic Properties Realized with Liquid‐Crystalline Ligands

“…Covering the surface of nanoparticles with properly designed LC ligands yields systems able to form nematic, smectic, and complex 3D structures . It was shown that the melting of LC affects the plasmonic properties of the material (i.e., causes the shift of SPR wavelength), therefore significant effort was directed at controlling the organization of nanoparticles by temperature .…”

Calculation of exchange integrals and Curie temperature for La-substituted barium hexaferrites

“…Owing to the large magnetocrystalline anisotropy, high Curie temperature T c and saturation magnetization M s , barium hexaferrites [BaFe 12 O 19 , BaM] are of great interest for magnetic recording, microwave magnetic devices, and permanent magnets123. Many schemes34567 have been attempted in the past few decades to improve the intrinsic magnetic properties of barium hexaferrites.…”