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Synthesis and Characterization of Superconducting Ferropnictide Bulks and Wires Jeremy Weiss

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Synthesis and Characterization of Superconducting Ferropnictide Bulks and Wires Jeremy Weiss Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2015 Synthesis and Characterization of Superconducting Ferropnictide Bulks and Wires Jeremy Weiss Follow this and additional works at the FSU Digital Library. For more information, please contact [email protected] FLORIDA STATE UNIVERSITY THE GRADUATE SCHOOL SYNTHESIS AND CHARACTERIZATION OF SUPERCONDUCTING FERROPNICTIDE BULKS AND WIRES By JEREMY WEISS A Dissertation submitted to the Department of Materials Science and Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy Degree Awarded: Spring Semester, 2015 Jeremy Weiss defended this dissertation on April 9, 2015. The members of the supervisory committee were: Eric Hellstrom Professor Directing Dissertation Gregory Boebinger University Representative David Larbalestier Committee Member Theo Siegrist Committee Member Per Arne Rikvold Committee Member The Graduate School has verified and approved the above-named committee members, and certifies that the dissertation has been approved in accordance with university requirements. ii This dissertation is dedicated to the memory of Professor James Brooks who served on this dissertation advisory committee until his passing in Fall 2014 iii ACKNOWLEDGMENTS Firstly, I would like to thank David Larbalestier for giving me the undergraduate opportunity to do the preliminary lab work that sparked an interest in applied research and ultimately lead to the following dissertation. To vaguely paraphrase the first toast of his I heard; an observation relevant to my developing career: “We never could have guessed that we would have ended up here, but we stumble through life as opportunities present themselves and it really is fascinating how it seems to work out for us.” It was David who introduced me to Jianyi Jiang who mentored me for two and a half years as an undergraduate. Jianyi showed an unfounded amount of patience as I learned to succeed (and fail) at research, was always willing to answer any question I brought him, taught me almost everything I know about electromagnetic characterization, and gave me the freedom to explore new techniques and procedures. I owe a lot of gratitude to Eric Hellstrom who mentored me as a graduate student. Eric taught me the most important skills I now possess including the ability to communicate effectively. With his help I have come from being a mess when presenting to winning multiple best presentation awards. I want to thank Bill Starch for purchasing, fixing, training, and managing of all things technical. When I first came to the ASC, I coveted Bill’s technically demanding job, and within a couple of years he trusted me enough to attempt almost any task I dared to take on, but there is only one Bill Starch. I’d like to thank the many scientists at ASC that have provided support. Chiara Tarantini provided many thoughtful discussions about fundamental theory and experimental techniques. Anitolii Polanskii, Fumitake Kametani, Dmytro (Dima) Abraimov, Van Griffin, and Akiyasu Yamamoto shared their characterization expertise and support. Ashleigh Francis, Muriel Hannion, Ben Hainsey, Ross Richardson, Matthieu Dalban-Canassy, Julian Velasquez, Jeff Whalen, Tiglet Basara, and Michael Santos all provided much needed technical support. Connie Linville and Charlotte Hall both went above and beyond when it came to providing wonderful administrative support. Jorge González, José Moreno, Marcos Corchado, and Gerardo Nazario were all National Science Foundation (NSF) sponsored research experience for undergraduate students whom I mentored over the summers on unique projects. I’d like to acknowledge the special opportunities I was awarded over the years, enabled by Eric Hellstrom and David Larbalestier, including financial support to attend summer schools funded by the Institute for Complex Adaptive Matter (ICAM), the National High Magnetic Field iv (NHMFL) Laboratory, and the FSU Research Foundation. I would also like to acknowledge supplemental financial support to attend conferences from the American Ceramic Society, and the NHMFL. I am grateful to the Institute of Electrical and Electronics Engineers (IEEE) Council on Superconductivity for awarding me a fellowship, without which ensuing unmanageable credit card debt was sure to become an extra burden. Last, and certainly not least, this work was supported by NSF DMR-1306785, NSF DMR-1006584, by the NHMFL which is supported by the NSF under NSF/DMR-0084173 and NSF DMR-1157490, and by the State of Florida. Work at the Atominstitut has been supported by the Austrian Science Fund (FWF): 22837-N20 and the European-Japanese collaborative project SuperIron (No. 283204). Atom- probe tomography measurements were performed at the Northwestern University Center for Atom-Probe Tomography (NUCAPT) and the LEAP tomograph was purchased and upgraded with funding from the NSF-MRI (DMR 0420532) and ONR-DURIP (N00014-0400798, N00014-0610539, N00014-0910781) programs. NUCAPT is a Shared Facility of the Materials Research Center of Northwestern University, supported by the National Science Foundation's MRSEC program (DMR-1121262). We are also grateful to the Initiative for Sustainability and Energy at Northwestern for upgrading NUCAPT’s capabilities. The work at the University of Tokyo was supported by the Japan Science and Technology Agency, PRESTO. I’d also like to individually acknowledge the members of my supervisory committee for their input, expertise, and guidance. Theo Siegrist taught me much about crystallography and a bit about interfacing with machines older than myself. Steven Van Sciver taught me everything I know about cryogenic and magnet design, and it was a great pity he was not available to see this dissertation through to the end. I’d like to thank Per Arne Rikvold for happily agreeing to serve on this committee. James Brooks was an exemplary role model for what every scientist and educator should be. He took on more work than anybody should while maintaining his trademark sense of humor about it. It was a tragedy to see him go, but I am thankful to have known him and am fortunate Greg Boebinger was willing to take his place on this committee. v TABLE OF CONTENTS List of Tables .................................................................................................................................. x List of Figures ................................................................................................................................ xi List of Symbols, Acronyms, and their Meanings ....................................................................... xvii Abstract ......................................................................................................................................... xx 1 - Introduction ............................................................................................................................... 1 1.1 – Background ................................................................................................................... 2 1.2 – Parallels Between FBS and Cuprates ............................................................................ 5 1.3 – Current Transport in Bulk Ferropnictides ..................................................................... 6 1.4 – Characteristic Lengths in Type-II Superconductors ..................................................... 8 1.5 – Bean’s Critical State Model ........................................................................................ 10 2 - Experimental Techniques ........................................................................................................ 11 2.1 – Introduction ................................................................................................................. 11 2.2 – Safety Considerations ................................................................................................. 11 2.3 – Synthesis Techniques .................................................................................................. 12 2.3.1 – Ambient pressure solid-state synthesis ..................................................... 12 2.3.2 – Mechanochemical synthesis...................................................................... 13 2.3.3 – Hot isostatic pressing ................................................................................ 13 2.3.4 – Wire fabrication ........................................................................................ 14 2.3.5 – Large bulk fabrication ............................................................................... 14 2.4 – Electromagnetic Characterization ............................................................................... 16 2.4.1 – SQUID magnetometry .............................................................................. 16 2.4.2 – M vs T measurements ............................................................................... 16 2.4.3 – Trapped remanent field measurements ..................................................... 17 2.4.4 – VSM magnetometry .................................................................................. 19 2.4.5 – M vs. H measurements .............................................................................. 20 vi 2.4.6 – Physical property measurements............................................................... 21 2.4.7 – R vs. (T, H) measurements ....................................................................... 21 2.4.8 – Ic vs. H measurements
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