NSF Nugget for FY06Investigating the scattering processes in MgB2

Work in the group of Newman and Rowell, Arizona State University, DMR0514592

Sept. 2006FRG on Two Gap Superconductivity

Wisconsin-Penn State- Arizona State-Puerto Rico-Mayaguez collaboration

DMR-0514592PI David Larbalestier, Eric Hellstrom and Paul Voyles

(UW), Zi-Kui Liu (Penn State), Nate Newman and John Rowell (Arizona State), and Oswald Uwakweh (U. Puerto

Rico Mayaguez)

Investigating the scattering processes in MgB2

Work in the group of Newman and Rowell, Arizona State University, DMR0514592 – in collaboration with Xi (Penn State)

The green area consists of data taken from samples that were damaged using high energy particles and carbon doped bulk samples. It seems that O doping also enhances Hc2 though not as strongly as C.

Understanding the role of scattering processes in MgB2 is of great practical importance as Hc2 of C-doped MgB2 films exceeds that of Nb-based conductor materials. Carrier scattering can be altered by varying the synthesis process, by doping, and by energetic particle irradiation. The effect of damage induced by 2-MeV alpha particles, followed by annealing, on the critical temperature (Tc), resistivity (), and upper critical field (Hc2), of MgB2 films made by different deposition processes has been studied. We also study the incorporation of oxygen into MgB2 films grown by MBE (at ASU). To increase carrier scattering, which in turn increases Hc2, many groups have doped MgB2, particularly with carbon. We find that MgB2 films with high oxygen content have reduced Tc but enhanced Hc2.

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Tc(K)

ASU O-doped films

PSU C-doped films

Hc2

(0)

(T)

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Tc(K)

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Tc(K)

ASU O-doped films

PSU C-doped films

Hc2

(0)

(T)

Education:Substantial progress has been made in designing and developing the project Science is Fun modules that address the National and Arizona Science Education Standards (Physical Sciences) associated with magnetism for elementary grades. Under direct supervision, two Science is Fun senior Interns have compiled a variety of exciting explorations for the modules. Field testing of the 15-minute presentation is expected to begin during the second half of the Fall semester, with field testing of the 45-minute presentation to begin in Spring 2007.

Societal Impact:A fundamental understanding of the scattering processes occurring within MgB2 is essential for MgB2 to reach its full potential. Once a reliable means of increasing Hc2 is obtained, MgB2 will be ready to compete with the existing Nb- based superconductors from which all MRI and high field magnets are made.

Investigating the scattering processes in MgB2

Group of Newman, Arizona State University, DMR-0514592

Please visit www.asu.edu/clas/csss/scienceisfun/index.html