Speaker
Description
The design of magnetic nanoparticles (MNPs) relies on the precise control of size, shape, and material composition, as these parameters critically influence their properties for applications in technology [1], biomedicine [2], and environmental science. Achieving optimal performance in a specific application requires a deep understanding of how the macroscopic properties of MNPs and their ensembles are governed by their nanoscale structural and magnetic characteristics. However, characterizing the magnetic morphology and internal spin structure of MNPs remains a significant challenge, as conventional macroscopic techniques often lack the spatial resolution required to probe these features accurately. To address these limitations, the magnetic Small-Angle Neutron Scattering technique with incident beam polarization (SANSPOL) has emerged as a powerful tool. SANSPOL enables the resolution of magnetization distributions at the nanometer scale, allowing for the disentanglement of spin disorder effects [3-4] and the distinct magnetization contributions from the core and shell regions in core$\\@$shell nanoparticles [5].
In this work, we investigate the influence of chemical composition on the magnetic structure of manganese (Mn)-doped ferrite MNPs. By systematically varying Mn doping levels in cubically shaped CoFe$_2$O$_4$ nanoparticles synthesized via the thermal decomposition method, we achieved uniform particle sizes and narrow size distributions ($\sigma_{log}<10\%$). We used SANSPOL to investigate the chemical homogeneity and magnetic morphology of the MNPs, revealing variations in surface spin disorder linked to Mn concentration. Additionally, we evaluated the heating performance of the Mn-doped MNPs under an alternating magnetic field to assess their potential for applications such as magnetic hyperthermia. By correlating heating efficiency with structural, chemical, and magnetic properties, we established a comprehensive relationship between composition and performance. This study advances the fundamental understanding of magnetic behavior in Mn-doped ferrite MNPs and provides practical guidelines for optimizing their properties for targeted technological and biomedical applications.
Acknowledgements
The authors thank ISIS Neutron and Muon Source for beamtimes (RB2210159 & RB2310314-1) and acknowledge support from the AMULET project supported by the Ministry of Education, Youth, and Sports of the Czech Republic (CZ.02.01.01/00/22_008/0004558), and co-funded by the EU.
References
[1] P. Bender et al., “Relating Magnetic Properties and High Hyperthermia Performance of Iron Oxide Nanoflowers,” The Journal of Physical Chemistry C, vol. 122, no. 5. American Chemical Society (ACS), pp. 3068–3077, Jan. 26, 2018. https://doi.org/10.1021/acs.jpcc.7b11255
[2] A. Lak et al., “Embracing Defects and Disorder in Magnetic Nanoparticles,” Advanced Science, vol. 8, no. 7. Wiley, Feb. 15, 2021. https://doi.org/10.1002/advs.202002682
[3] D. Zákutná et al., “Field Dependence of Magnetic Disorder in Nanoparticles,” Physical Review X, vol. 10, no. 3. American Physical Society (APS), Jul. 24, 2020. https://doi.org/10.1103/physrevx.10.031019
[4] M. Gerina et al., “Size dependence of the surface spin disorder and surface anisotropy constant in ferrite nanoparticles,” Nanoscale Advances, vol. 5, no. 17. Royal Society of Chemistry (RSC), pp. 4563–4570, 2023. https://doi.org/10.1039/d3na00266g
[5] D. Zákutná et al., “Magnetic Coupling in Cobalt-Doped Iron Oxide Core–Shell Nanoparticles: Exchange Pinning through Epitaxial Alignment,” Chemistry of Materials, vol. 35, no. 6. American Chemical Society (ACS), pp. 2302–2311, Mar. 09, 2023. https://doi.org/10.1021/acs.chemmater.2c02813
