Self-consistent simulation approach to magnetic soft matter

Context To reveal the fundamental relationship between the shape/internal structure of magnetic colloidal particle and acting magnetic/mechanical/hydrodynamic forces, on one side, and resulting dynamic magnetic response, on the other, is crucial to optimise applications of magneto-controllable systems, such as hyperthermia. However, in order to understand such a complex interplay, one needs a qualitatively new approach that will take into account both particle intrinsic magnetisation dynamics and their spatial rearrangements/self-assembly. Objectives SAM aims at investigating the behaviour of magnetic colloids in fluid and gel carriers in AC magnetic fields from both fundamental and applied perspectives. First, a method to obtain a self-consistent solution of the Langevin equations of motion for magnetic colloids combined with magnetisation dynamics of individual particles in both liquid and gel carries at finite temperature will be developed. Second, we will use this method to study Neel and Brownian heating mechanisms in hyperthermia, providing a detailed description of both as a function of properties of the magnetic particles (magnetic anisotropy, saturation magnetisation, shape, size and density) as well as the properties of the carrier (viscosity for liquids and elasticity for gels). Originality Such a study has not been performed yet, as it requires to bridge together Physics of Magnetism and Soft Matter. The joint effort to deeply understand dynamics of magnetic soft matter, as proposed in SAM, is essential in order to make a step forward in the development of new smart materials with targeted applications. Methods We employ a unique combination of methods: coarse-grained molecular dynamic simulations of magnetic soft matter on particle level and thermally activated micromagnetics of solid materials inside the particles. Experimental verification for available anisometric particle systems via magnetic measurements will be performed by the National Research Partner. Primary researchers involved Ass. Prof. Sofia. S. Kantorovich will lead the project and supervise one of the PhD students. She will provide her expertise in coarse-grained computer simulation in soft matter. Ass. Prof. Dieter Suess will supervise another PhD student. He will provide his expertise in micromagnetic simulations, solid state physics and magnetic measurements.

Magnetic colloids-tiny magnetic particles dispersed in liquids or soft gels-are key components of many emerging technologies, including biomedical applications such as magnetic hyperthermia for cancer treatment. In these systems, external alternating magnetic fields cause the particles to move, rotate, and change their magnetic state, generating heat or other useful responses. The efficiency and controllability of these effects depend in a complex way on the particles' size, shape, internal structure, and on how they interact with their surrounding medium. Despite their importance, the fundamental link between the internal magnetic dynamics of individual particles, their collective motion and self-assembly, and the resulting macroscopic magnetic response is still not fully understood. Addressing this challenge requires a new, integrated approach that treats magnetic and mechanical effects on an equal footing. The SAM project aims to uncover these relationships by studying magnetic colloids in both liquid and gel-like environments under alternating magnetic fields. We will develop a novel theoretical and computational framework that simultaneously describes the magnetic behaviour inside each particle and the motion and rearrangement of particles in the surrounding soft material, including the effects of thermal fluctuations. Using this approach, we will investigate the two main mechanisms responsible for heat generation in magnetic hyperthermia-Néel and Brownian relaxation-and analyse how they depend on particle properties such as size, shape, magnetic anisotropy, and magnetisation, as well as on the viscosity or elasticity of the carrier medium. Theoretical predictions will be validated through magnetic measurements on experimentally available particle systems. By bridging the fields of magnetism and soft-matter physics, SAM will provide new fundamental insights into the dynamics of magnetic soft materials. These results will support the rational design of next-generation magnetically controllable systems with improved performance in biomedical and technological applications.