Magnetic Dissipation in Ferrofluids

TL;DR

This paper provides a comprehensive overview of magnetic dissipation mechanisms in ferrofluids, emphasizing the importance of frequency-dependent susceptibility and validating theoretical predictions with experimental calorimetric data.

Contribution

It introduces a unified framework for understanding energy dissipation in ferrofluids and correlates magnetometry with calorimetric measurements across a broad frequency range.

Findings

Magnetometry-based predictions align with calorimetric results.

Frequency-dependent susceptibility is key to understanding dissipation.

Experimental validation conducted with magnetite nanoparticle ferrofluid.

Abstract

Ferrofluids, composed of magnetic nanoparticles suspended in a non-magnetic carrier liquid, have attracted considerable attention since their discovery in the 1960s. Their combination of liquid and magnetic properties gives rise to complex behaviors and unique functionalities, enabling a wide range of technological applications. Among these is the ability of the magnetic material to be moved by and to absorb heat when exposed to an external magnetic field -- a process that can occur through various dissipation mechanisms depending on the system. A detailed understanding of these mechanisms is crucial for tailoring materials to specific applications. We provide a comprehensive overview of the theoretical principles underlying different energy dissipation processes and propose a coherent framework for their interpretation. Particular attention is devoted to describing the frequency-dependent susceptibility, which is the key parameter to describe dissipation. We demonstrate that dissipation, predicted from magnetometry-based studies, matches well with direct, frequency-dependent calorimetric results, expanding the available frequency range of the characterization. The demonstrating measurements were carried out with a dilute ferrofluid containing magnetite nanoparticles of a mean diameter of 10.6 nm.