Hard meets soft: tuning binary ferrofluids
- Author(s)
- Malika Khelfallah, Ekaterina V. Novak, Andrey A. Kuznetsov, Deniz Mostarac, Niéli Daffé, Marcin Sikora, Sophie Neveu, Jovana Zečević, Johannes D. Meeldijk, Dario Taverna, Philippe Sainctavit, Mauro Rovezzi, Hebatalla Elnaggar, Enzo Bertuit, Nicolas Mille, Rachid Belkhou, Vincent Dupuis, Claire Carvallo, Amélie Juhin, Sofia S. Kantorovich
- Abstract
We study binary ferrofluids composed of multicore “nanoflowers” of magnetically hard CoFe2O4 and magnetically soft MnFe2O4, as a way to optimise heat dissipation while suppressing aggregation–properties essential for biomedical applications. Bulk magnetometry and molecular dynamics simulations were combined to elucidate their behaviour. Experiments show wasp-waisted hysteresis, composition-dependent coercivity, and strong protocol dependence (field cooling). Simulations reproduce these trends and reveal the underlying structure–property coupling: (i) in an applied magnetic field, CoFe2O4 forms chains that dominate collective switching; (ii) adding MnFe2O4 “poisons” these chains—shortening and de-branching clusters—thereby lowering coercivity and loop area relative to a weighted superposition of the individual component responses without interactions; (iii) dipolar coupling reciprocally hardens the magnetically soft phase and softens the magnetically hard phase even without large-scale aggregation; and (iv) at higher total volume fraction (ϕ = 0.1) magnetically soft particles still suppress chain growth, reducing mean cluster size by up to an order of magnitude while keeping heating-relevant hysteresis close to Stoner–Wohlfarth expectations. These results establish composition-controlled microstructure as a means to decouple thermal output from aggregation: CoFe2O4 : MnFe2O4 mixtures can be tuned to enhance loss mechanisms while mitigating aggregation, offering a route to binary ferrofluids optimized for magnetic hyperthermia and drug delivery.
- Organisation(s)
- Computational and Soft Matter Physics
- External organisation(s)
- Sorbonne University, Ural Federal University, Synchrotron SOLEIL, AGH University of Science and Technology, Utrecht University, European Synchrotron Radiation Facility ESRF, University of Grenoble Alpes, Météo-France, Observatoire des sciences de l'univers de Grenoble
- Journal
- Nanoscale
- Volume
- 18
- Pages
- 11724-11738
- No. of pages
- 15
- ISSN
- 2040-3364
- DOI
- https://doi.org/10.1039/D5NR05218A
- Publication date
- 03-2026
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103015 Condensed matter
- ASJC Scopus subject areas
- General Materials Science
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/5fb42da1-7467-4159-8a5e-d27c1b856549