UCLA

Magnetic nanoparticles show promise in a vast array of devices that utilize control of nano magnetism. For these devices to properly function, the magnetic properties of the nanomaterials must be precise and uniform across the synthesized materials. The focus of the work that is presented here is to develop ways of characterizing nanoparticles to better understand the materials. Further to the work is to show how to create improved nanoparticles which can be used in eventual nanoscale magnetic devices.The first three chapters of this work show ways to improve the nanoparticle materials used in eventual nanoparticle based magnetic devices. Chapter one is concerned with improving a method for adhering nanoparticles to surfaces to later manipulate their magnetic moments. The method alters a synthetic method for nickel nanoparticles to remove a phosphorus impurity allowing for an air-free adhesion method. Thus, the method avoids oxidation damage to the nanoparticle magnetic properties. The second chapter displays the development of a new nanoparticle synthetic method for cobalt ferrite nanoparticles. The new method improves size dispersity and shows a higher degree of size control. Further, the magnetic properties of these crystals are shown to be superior. The third iv chapter shows the adaptation of a known magnetostrictive material galfenol, an iron gallium alloy, into a nanoparticle. This is the first synthesis of such a material as a processable solution nanoparticles and is shown to be able to be adhered to surfaces using the methodology in chapter 1. The remainder of the chapters of this work are methodologies of measuring nanoparticles to generate a better understanding of the structure of those nanoparticles and how this can help improve magnetic nanoparticle systems downstream. Chapter 4 involves using combined surface sensitive and bulk stoichiometry measurements to create a picture of the nanoparticle atomic distribution. The example system of annealing of FePt nanoparticles is used to show the value of this method. Finally in Chapter 5 a novel mathematical fitting of nanoparticle anisotropy distributions is shown. This method is used to calculate a temperature dependent anisotropy constant inherent to the chemical structure of the nanoparticles revealing important information about the synthetic process. Further surface and shape anisotropies are propped to provide a fuller picture of nanoparticle quality and thus understand methods of improving synthesis.