Summer Research Experience for Teachers
In the summer of 2007, the following teachers have joined the MRSEC team:
“This summer, with the goal of attaining a core shell structure, I continued research with sputtered CuFe clusters. I also worked with ball-milled Nd-Fe-B. This was in an attempt to reduce the size yet enhance the properties of high-energy permanent magnets. As “nano” becomes a buzz word in the news, I can speak from first hand experiences. These experiences allow me to infuse nanomagnetic research into my high school classroom.”
“This summer I am continuing my MRSEC work with Dr. Ducharme’s capacitor project. We are testing the ferroelectric properties of the polymer PVDF, with current focus on the iodine oligomer. A ferroelectric material’s molecules are all aligned in the same direction giving a uniform polarization that can be manipulated and switched by an external electric field. This can be useful for computer data storage.”
“My MRSEC internship this summer centered on the fabrication of Fe microbeads. These beads will be used at Los Alamos for research projects they are doing with magnetic separation, and biological targeting. This was an entirely new experience for me, and gave me many new insights into how broad research in Physics has become, and how many different disciplines in science it involves.”
“For my summer MRSEC internship, I had the privilege of working in Dr. Tan’s engineering mechanics group focusing on polymer nanofabrication. The purpose of the research was to determine better processes to formulating breath figure complexes. The process for forming breath figures is by running humid air over a hydrophobic solution with dissolved polystyrene. As the solution evaporates water droplets embed and form breath figure structures. Our work was utilizing different insoluble seed compounds to determine if we could consume fewer raw materials while still generating well-ordered breath figure arrangements. Long-term impact of this branch of research includes ant-adhesive and anti-reflection coatings, tailored interfaces for solar cells, and tissue implantation.
The biggest impact for me this summer is the real-world experience and activities I will be able to bring back to the classroom and excite students about the limitless opportunities in nanotechnology and science pursuits.”
“This summer I have been working on a project with the intention of optimizing a magnetic characterization technique which measures the magneto-optic Kerr effect in magnetic thin films. The Kerr effect describes the phenomenon of changes in the polarization state of light when it is reflected by a magnetized sample. Specifically, linearly polarized monochromatic light is transformed into elliptically polarized light upon reflection. In addition to the reflection-induced ellipticity, the large axis of the polarization ellipse is slightly rotated with respect to the polarization plane of the incoming light. This rotation is quantified by the Kerr rotation angle. Both the Kerr rotation and the Kerr ellipticity are in good approximation proportional to the magnetization of the sample. Therefore, the Kerr effect allows us to measure the dependence of the magnetization of a sample as a function of the applied external magnetic fields and temperature. The Kerr rotation and Kerr ellipticity can be determined from an intensity measurement of the reflected light when the polarization state of the reflected light is analyzed by a polarizer located in front of a photosensitive diode. In order to increase the signal-to-noise ratio, Dr. Binek’s lab uses a modulation technique allowing the application of phase sensitive detector methodology by means of a lock-in amplifier.
This measurement requires a complex setup consisting of a laser diode as a monochromatic and roughly linearly polarized light source, a polarizer, the sample, a photo-elastic modulator, an analyzer and the photo-detector. While the modulation technique is in principle well known, there are various arrangements of the optical components which yield similar but not identical results from the point of view of signal-to-noise optimization. It was my task to analyze a set of possible arrangements of the optical elements where the position of the modulator and the relative orientations of the polarizer and analyzer with respect to each other and with respect to the modulator retardation axis have been systematically changed. My goal was to theoretically determine the best configuration with respect to the signal-to-noise ratio by using Jones matrix calculations. In addition to this theoretical analysis, we confirmed our conclusions experimentally by measuring hysteresis loops and the corresponding signal-to-noise ratios of the loops for each configuration. We analyzed various configurations where the first and/or second harmonic of the periodic light intensity turned out to be directly proportional to the off-diagonal elements of the dielectric tensor containing the magnetic information. The optimized setups are free from large field-independent contributions which originate from the diagonal elements of the dielectric tensor. Some of these setups appear to be counterintuitive. The results of my work could provide valuable information regarding the optimization and theoretical understanding of the configurations used to measure the Kerr effect.”