Date of Award
2015-01-01
Degree Name
Master of Science
Department
Physics
Advisor(s)
Cristian E. Botez
Abstract
We have investigated the effect of dipolar interactions on the superspin blocking and freezing of 10 nm average size Fe3O4 magnetic nanoparticle ensembles. Our dynamic susceptibility data reveals a two-regime behavior of the blocking temperature, TB, upon diluting a Fe3O4/hexane magnetic nanoparticle fluid. As the nanoparticle volume ratio, Phi, is reduced from an as-prepared reference Phi = 1 to Phi = 1/96, the blocking temperature decreases from 46.1 K to 34.2 K, but higher values reenter upon further diluting the magnetic fluid to Phi = 1/384 (where TB = 42.5 K). We show that cooling below TB within the higher concentration range (Phi > 1/48) leads to the collective freezing of the superspins in a spin-glass-like fashion, whereas individual superspin blocking occurs in the presence of weaker dipolar interactions (Phi < 1/96). The unexpected increase of the blocking temperature with the decrease of the interparticle interactions observed at low nanoparticle concentrations is well described by the Mørup-Tronc (MT) model.
Language
en
Provenance
Received from ProQuest
Copyright Date
2015
File Size
38 pages
File Format
application/pdf
Rights Holder
Joshua Logan Morris
Recommended Citation
Morris, Joshua Logan, "AC-Susceptibility Investigations of Superspin Blocking and Freezing in Interacting Magnetic Nanoparticle Ensembles" (2015). Open Access Theses & Dissertations. 1106.
https://scholarworks.utep.edu/open_etd/1106