1. Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
2. Ames National Laboratory-USDOE, Ames, IA 50011, USA
3. Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
4. Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
5. Department of Physics, University of Alabama at Birmingham, Birmingham, AL 35294-1170, USA