Year
2005
Degree Name
Masters of Science - Research
Department
Institute for Superconducting and Electronic Materials - Faculty of Engineering
Recommended Citation
Winton, Brad, A study of the magnetoresistance effect in Bi-2212 for the purposes of utilisation in magnetic field sensors, M.Sc. thesis, Institute for Superconducting and Electronic Materials, University of Wollongong, 2005. http://ro.uow.edu.au/theses/318
Abstract
The magnetoresistive (MR) effect in Bi-2212 was studied through the creation of a number of Bi-2212 composites for the purposes of utilization as the active component in a magnetic field sensor. Bi-2212/USr2CaO6, Bi-2212/MgO, Bi-2212/CeO2 and Bi-2212/Ag composites were made with varying concentrations of impurities. The MR effects of these composites were characterized and compared to that of pure Bi-2212 and that of the other composites. The resistivity of the Bi-2212 composites with the exception of the Bi-2212/CeO2 and Bi-2212/Ag can be characterized by a high sensitivity to applied magnetic field over an increasing temperature range with increasing impurities concentrations up to a percolative limit. Bi-2212/CeO2 composites display a highly insulating behavior indicative of a breached percolative limit while the Bi-2212/Ag composite displays a decreased resistance as the Ag improves conductivity with the HTS. X-ray results show the compatibility of the added impurities with the stability of the Bi-2212 matrix in all cases except CeO2 addition during the melt texturing (MT) process. Bi-2212/USr2CaO6 and Bi-2212/MgO showed the most potential for cryogenic magnetic field sensing applications, and so Bi-2212 + 6.6wt% USr2CaO6 MT composite and Bi-2212 + 20wt% MgO MT composite were tested at 77K and cycling fields of 0-1T. They showed high sensitivity to applied magnetic fields and no hysteresis. Bi-2212 + 20wt% MgO MT composite bulk proved to be the most promising composite for the purposes of cryogenic magnetic field sensing, and so a prototype cryogenic sensor was built with Bi-2212 + 20wt% MT composite bulk as the active component.
Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.