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Senior Undergraduate Students Presentations

Jenniffer Roames and Tim Young

Physics Department

The University of Memphis

April 12th, 2006, 4:00pm, Manning Hall 201

Refreshments served at 3:30pm, Manning Hall 222

TRACE: Isothermal "Eyes" Only?

Jennifer Roames

Even though the Sun is the most studied star, we do not know everything about it. One unanswered question is the “coronal heating problem.” The surface of the Sun is approximately 5800 K. However, the solar atmosphere (corona) extends more than a million kilometers from the surface of the Sun and reaches temperatures greater than 1,000,000 K. There are many theories as to how the corona is heated. One is by studying the temperature along coronal loops that are formed when plasma follows the twisted magnetic field of the Sun.

The loops extend many thousands of kilometers above the Sun’s surface. To support these theories it must be determined whether these loops are preferentially heated at the footpoints or the apex. The Transition Region and Coronal Explorer (TRACE) has provided many spectacular images of these solar loops. TRACE also has the ability to calculate temperature along these loop structures. After studying many TRACE loops our data gave us the same answer every time. Which was that each loop had the same temperature, 1.2 MK. An important question is why is the temperature always the same? Tune in to find out the answer.

Core-shell Ferromagnetic-Antiferromagnetic Nanocomposite

Tim Young

Permanent magnetic materials currently available in the market are based on the rare earth transition metal alloys such as Sm2Fe17Nx and Nd2Fe14B. The strength of the magnet, energy product (BHmax), is defined by the maximum area under the second quadrant of the hysteresis loop; i.e. squarness of the loop. Thus, an increase in the strength of the magnet can be brought in by increasing the coercivity and remanence of the hysteresis loop.

In theory coercivity and remanence enhancement for a magnetic material is possible via exchange bias interaction between ferromagnetic (FM) and antiferromagnetic (AFM) phases in contact. We have synthesized core-shell ferromagnetic-antiferromagnetic nanocomposite, Fe2O3 (FM)-NiO (AFM) material via hydrothermal synthesis technique. Details of the structural measurements including XRD, TGA and TEM along with magnetization measurements will be presented. The magnetization measurements indeed show an increase in the coercivity and the remanence of Fe2O3-NiO composite.

Encouraged by these results we are in a process of synthesizing Sm2Fe17Nx-NiO/CoO nanocomposite magnets. Our research has great industrial significance because FM-AFM nanocomposites will use less rare-earth element compared to pure Sm2Fe17Nx but still be able to maintain high energy product. This will reduce the cost of magnet and increase their environmental stability.

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