Abstract

Magnetic nanoparticles are used in nanotechnologies and biomedical applications, such as drug targeting, hyperthermia treatment, MRI contrasting agents, and bio-separation of compound solutions. Magnetite (Fe3O4) nanoparticles stand to be effective in these roles due to the non-toxic nature of magnetite and its strong magnetization. To this end, a greater understanding of the magnetic behavior of the individual magnetite nanoparticles is needed when a collection of them is used. This research seeks to discover the local magnetic ordering and dynamics of fluctuations of ensembles of magnetite nanoparticles at various stages of the magnetization process, throughout the superparamagnetic blocking transitions, and for various particle sizes. We use x-ray circular dichroism and x-ray resonant magnetic scattering (XRMS), which provides information about the various magnetic orders in the samples. We discuss the modeling of the magnetic scattering data using a one-dimensional chain of nanoparticles in real space as well as an empirical Gaussian packet model in reciprocal space. We find that at low temperature, and field values close to the coercive point, magnetite nanoparticles experience a significant amount of antiferromagnetic ordering which increases with particle size. We present real space magnetic images of the nanoparticles obtained via dichroic x-ray ptychography, which confirm our predictions from scattering. Finally, we investigate the dynamics of magnetic fluctuations by using x-ray photon correlation spectroscopy.

Degree

PhD

College and Department

Computational, Mathematical, and Physical Sciences; Physics and Astronomy

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-08-20

Document Type

Dissertation

Keywords

magnetite, nanoparticles, magnetic scattering, XRMS, computational modeling, ptychography, XAS, XMCD, XPCS

Language

english

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