Access Type
Open Access Dissertation
Date of Award
January 2015
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Physics and Astronomy
First Advisor
BHANU P. JENA
Second Advisor
CHRISTOPHER V. KELLY
Abstract
The study of magnetic nanoparticles is of great interest because of their potential uses in magnetic-recording, medical diagnostic and therapeutic applications. Additionally, they also offer an opportunity to understand the physics underlying the complex behavior exhibited by these materials. Two of the most important relaxation phenomena occurring in magnetic nanoparticles are superparamagnetic blocking and spin-glass-like freezing. In addition to features attributed to superparamagnetism, these nanoparticles can also exhibit magnetic relaxation effects at very low temperatures (≲ 50 K). Our studies suggest that all structural defects, and not just surface spins, are responsible for the low-temperature glass-like relaxation observed in many magnetic nanoparticles. The characteristic dipolar interaction energy existing in an ensemble of magnetic nanoparticles does not apparently depend on the average spacing between the nanoparticles but is likely to be strongly influenced by the fluctuations in the nanoparticle distribution. Our findings revealed that incorporating a small percentage of boron can stabilize the spinel structure in Mn3O4 nanoparticles. We have also demonstrated that the dipolar interactions between the magnetic cores can be tuned by introducing non-magnetic nanoparticles. In particular, we studied the magnetic properties of Gd-doped Fe3O4 nanoparticles, a potential applicant for T1–T2 dual-modal MRI contrast agent. We have explored the interactions of BiFeO3 nanoparticles on live cells and the binding of FITC-conjugated Fe3O4 nanoparticles with artificial lipid membranes to investigate these materials as candidates in medical imaging. Taken together, these studies have advanced our understanding of the fundamental physical principles that governs magnetism in magnetic materials with a focus on developing these nanoparticles for advanced biomedical applications. The materials developed and studied expand the repertoire of tools available for multimodal imaging, using both x-ray and magnetic resonance.
Recommended Citation
Laha, Suvra Santa, "Understanding The Physics Of Magnetic Nanoparticles And Their Applications In The Biomedical Field" (2015). Wayne State University Dissertations. 1343.
https://digitalcommons.wayne.edu/oa_dissertations/1343