Comparing the magnetocaloric effect in
single crystal and polycrystal La1-xSrxMnO3
Brian Myer, Appalacian State University, (Advisor: John Neumeier)
The thermodynamic properties of ferromagnetic La1-xSrxMnO3 (0.15 ≤ x ≤ 0.19) were investigated. They are a representative group of manganates under scrutiny for potential use a magnetorefrigerant. The change in magnetic entropy was calculated from magnetization and heat capacity data gathered in the 0 ≤ H ≤ 2 tesla range. A smaller heat capacity than found in prior reports leads to a large maximum adiabatic temperature change of approximately 6 K. This large value of |∆T| increases the promise of the manganese perovskites as candidates for applications in room temperature magnetic refrigeration.
Link to Brian's publication in
Physical Review B: MagCaloCrystal.pdf
At left, Brian is pictured near the optical image furnace. This device is used to grow single crystals of complex materials. It can reach 2150˚C using two high-powered lamps (up to 3500 watts) in elliptical cavities. The light is focused on the sample to produce the high temperature region.
High
Finesse Fabry-Perot Interferometer for 793nm Tunable Diode Laser
Gregory Zicarelli, San Francisco State University, (Advisor: Rufus Cone)
A high finesse was constructed using a 15 cm long ultra low expansion glass spacer with a 3/16" bore down the center. At each end of this bore are two mirrors with 20 cm radius of curvature and 99.99% reflectivity. A 793 nm tunable diode laser is mode-matched to the cavity in order to measure the cavity ringdown time. The exact reflectivity of each mirror was found to be 99.958%.
At left, Greg is pictured giving a presentation on his project. At the end of the REU program, a one day seminar session is held where each student has the opportunity to tell everyone about their research projects.
High
Temperature Impedance Spectroscopy System for Solid Oxide Fuel Cell
Ceramics
Arnold Braker, University of Oklahoma, (Advisor: Hugo Schmidt)
The development of high performance ceramics for use in Solid Oxide Fuel Cells could lead to improved efficiency and decreased cost. Impedance spectroscopy is one method of examining the properties of these materials. Because SOFCs operate at high temperatures, we will use impedance spectroscopy in a temperature range of 100 ˚C-900 ˚C. Specifically, we plan to study the grain and grain boundary of ceramics. In my project, I developed Labview Software to run these impedance spectroscopy measurements. I also researched improvements for the high temperature sample holder.
At left, Arnold hikes down from Saddle Peak in the Bridger Mountains. Saddle Peak is at 9000 ft, and the hike winds through Upper Cottonwood Canyon along a mountain stream. This hike was one of the outings arranged by the MSU REU Materials and Solar Physics Programs in 2004.
Scott,
far left, rafting on the Yellowstone river
with other REU participants.
with other REU participants.
Atomic Force Biosensors: Detection
and characterization of single molecule antibody-antigen interactions
via atomic force microscopy
Scott Randall, University of Washington, Seattle, (Advisor: Recep Avci)
By covalently bonding antibody-terminated polymer tethers to an atomic force microscope (AFM) tip, it is possible to study antibody interactions with a biological surface. In order to verify the chemical attachment of these polymer tethers, the AFM tip surface chemistry was characterized via x-ray photoelectron spectroscopy (XPS). Using these data, the tether attachment protocols were refined to allow better surface coverage by first washing the silicon nitride tips in piranha solution (H2O2 & H2SO4). These improved tips were then compared with similar chemically modified tips to ascertain the efficacy of the new product.
Measuring Anisotropy With the Surface
Magneto-optic
Kerr Effect
Kerr Effect
Kyle Story, Cornell University, (Advisor: Yves Idzerda)
This summer was spent sudying the Surface Magneto-Optic Kerr Effect and its uses in characterizing thin magnetic films. By measuring changes in the intensity of polarized light reflected off of samples in variable external magnetic films, hysteresis loops are obtained and Coercive Field and Magnetic Remnance values are extracted. The degree to which these values depend on the orientation of the sample is reflected by a property called Anisotropy. The Anisotropy constants for a new material, Co2MnSi/GaAs, were measured.
At left, Kyle is pictured giving a presentation on his project. At the end of the REU program, a one day seminar session is held where each student has the opportunity to tell everyone about their research projects.
Ben, far left, at the trail head for the hike to Saddle Peak. This hike was organized by Prof. Hugo Schmidt (2nd
from right) and is playfully named "Hugo's Death March".
Calidistat Design and Construction for use
with Varian E-Line Century Series Spectrometer and Angular Variation of
KNbO3 at Room Temperature
Ben Losby, Montana State University, (Advisor: Galina Malovichko)
In studying crystal such as potassium niobate (KNbO3) it is advantageous to observe changes in the electron paramagnetic resonance (EPR) spectra as the crystal undergoes phase changes. To accomplish this it is necessary to integrate a heating system (Calidistat) that allows the acquisition of EPR spectra at temperatures in excess of 600 ºC. One approach to a solution will be offered. In addition, the obtained spectra for the angular variation of KNbO3 at room temperature will be presented.