Four-Year College Faculty-Student Team Fellowships Program
n summer 2009, the following faculty/student teams joined the MRSEC group:
“This summer our work was focused on fabrication and characterization of Pt/Co and Co/Pd perpendicular magnetic heterostructures and Cr2O3 thin films using molecular beam epitaxy (MBE). The growth mechanism and film thickness were monitored in-situ using reflection high energy electron diffraction (RHEED). X-ray reflectivity and atomic force microscopy (AFM) measurements were carried out for measuring film thickness.
The orientation and crystallinity of the films were studied using X-ray diffraction (XRD). In order to understand the perpendicular magnetic anisotropy, the heterostructures were investigated using a superconducting quantum interference device (SQUID) and an alternating gradient force magnetometer (AGFM).”
Todd's Project: “I worked on micromagnetic simulation of two different systems. (1) I looked at how the morphology if Co in a SmCo5/Co alloy affects the magnetic properties of the sample and (2) I simulated the effects of surface anisotropies of FePt nanoclusters on the magnetic properties of the clusters.”
Marks Project: “My task is to magnetically characterize the Eutectic region of the phase diagram of Gadolinium/Boron alloys using the melt spin technique for alloy production. Throughout my characterization I have been looking for evidence of an amorphous structure. So my project, in short, is the magnetic characterization of a possibly amorphous mixture of Gd and B.”
“Our work this summer consisted on the adsorption of isomers of 1,2-diodobenzene, 1,3-diodobenzene and 1,4-diodobenzene on zwitterion p-benzoquinonemonoimine compound from the class of N-alkyldiaminoresorcinones (or 4,6-bis-dialkylaminobenzene-1,3-diones, i.e. C6H2(NHR)2(O)2), where R=C4H9), on a gold substrate. Zwitterions are spin coated on a gold substrate and we find that the molecule bonds to the surface through the imines group forming fairly uniform films. Selective adsorption from the gas phase of the diodobenzenes has been observed on the zwitterion surface. The molecular preferential orientation and substrate interactions upon adsorption seems to be influence by their strong dipole-dipole interactions and molecular structure.”
“This summer our goal was to produce an inexpensive, room-temperature, atmospheric-pressure scanning tunneling microscope (STM) with atomic resolution. Our prototype uses slip-stick motion for coarse approach to the surface to be imaged. Motion of the tip is accomplished with four flat piezoelectric translators that provide both z-motion (slip-stick) as well as the x-y scanning motion. Maximum x-y scan range is approximately 1.7 µm x 1.7 µm and the fine z-motion range is estimated to be about 570 nm. The x-y scan range was calculated from the piezo constants and from measurements of the deflection of a laser reflected from a mirror mounted on the tip. Both values agreed to within about 10%. When driven by a 16-bit DAC (digital to analog converter) these ranges correspond to step sizes of 0.025 nm in x and 0.01 nm in z. Increasing the gain of the piezo drive amplifiers can reduce these step sizes but we will be limited by the noise levels. So far, the prototype has a noise level of about 0.05 nm. Eventually we will incorporate a digital signal processing microcontroller to drive the DACs, read the tunnel current, and provide the interface to the electronics (possibly even adding an LCD screen for local display of the images). Materials for the prototype total about $300.”
The MRSEC research of the UTPA Professor (Mircea Chipara) – Student (Thomas Mion) pair was focused on ferroic nanocomposites. The student concentrated his research on the synthesis of ferroelectric-magnetic bilayers. His work was focused on the deposition of thin films of perovskites - a magnetic material with potential applications in future spintronics devices. The obtained thin films were characterized by structural techniques (X-Ray Diffraction and electron microscopy) as well as by preliminary magnetic and electric testing. Future detailed magnetic and electric measurements on thin films of perovskites covered by ferroelectric polymers will be performed.
The research activity of the professor concentrated on two directions: 1. Investigations on the physical properties of lanthanum lead perovskites. These work implied structural measurements (X-Ray diffraction and microscopy), electric measurements, as well as extensive ferromagnetic resonance measurements at various temperature, near Curie temperature. Details regarding the magnetocrystalline anisotropy were obtained by ferromagnetic resonance and confirmed by MOKE experiments on the same samples. The coexistence of paramagnetism and ferromagnetism in the vicinity of Curie temperature was observed. A paper that contains these results is under preparation.
2. Synthesis of ferroics nanocomposites by dispersing nanometer-sized magnetic nanoparticles (Fe3O4 purchased from Sigma Aldrich) within a soluble fluorinated ferroelectric copolymer, available from Sigma Aldrich. The nanocomposites were obtained by dissolving the polymer in dimethylformamide, addition of magnetic nanoparticles to the solution and sonication of the fluid mixture for several hours. The sonication is required to improve the dispersion of magnetic nanoparticles within the polymeric matrix. Two concentrations were prepared, one containing 20 %wt. Fe3O4 and the other containing 40 %wt, magnetic nanoparticles. Thin films of such ferroic nanocomposites were obtained by spin coating. Preliminary experimental data confirmed the magnetic and ferroelectric characteristics of the composite. Further measurements are required to assess the coupling between electric and magnetic properties.