Effective Landau theory of ferronematics

TL;DR

This paper develops an effective Landau theory for ferronematics, describing their magnetic and nematic properties based on microscopic models, and predicts complex responses to weak magnetic fields.

Contribution

It introduces a quantitative Landau-like framework for ferronematics derived from microscopic and density functional theories, capturing magnetization-nematic coupling.

Findings

Predicts ferromagnetic phase in ferronematics.

Provides quantitative coupling between magnetization and nematic director.

Describes complex mesoscopic response patterns to magnetic fields.

Abstract

An effective Landau-like description of ferronematics, i.e., suspensions of magnetic colloidal particles in a nematic liquid crystal (NLC), is developed in terms of the corresponding magnetization and nematic director fields. The study is based on a microscopic model and on classical density functional theory. Ferronematics are susceptible to weak magnetic fields and they can exhibit a ferromagnetic phase, which has been predicted several decades ago and which has recently been found experimentally. Within the proposed effective Landau theory of ferronematics one has quantitative access, e.g., to the coupling between the magnetization of the magnetic colloids and the nematic director of the NLC. On mesoscopic length scales this generates complex response patterns.