Year of Publication
Arts and Sciences
Physics and Astronomy
Lance E. De Long
Many advances in technology ranging from biology and medicine through engineering and computer science to fundamental physics and chemistry depend upon the capability to control the fabrication of materials and devices at the submicron scale. Quantum mechanical effects become increasingly important to atomic and molecular interactions as the distances between neighbors decrease. These effects will provide materials and device designers with additional flexibility to establish properties of the designers choice, but the cost of this additional flexibility must be paid in the complexity of nonlinearities entering the interactions and the design process. The work presented here has provided several early results on three such interactions among closely-spaced submicron material structures: 1) the properties of superconductivity have been studied, 2) the properties of ferromagnetism have been studied, and 3) the interactions between superconductivity and ferromagnetism have been studied. Since our work was published, there has been considerable interest in all three of these wide-open areas and hundreds or thousands of additional results are now in the literature. We have used standard methods from the semiconductor industry as well as innovative methods to fabricate micron and submicron devices for observation. Standard optical lithography and standard electron beam lithography have been implemented to shape micron and submicron structures, respectively. Additionally, a laser interferometric lithography method has been invented and used to shape submicron structures. The materials used were vanadium, niobium, nickel, and/or permalloy. We have utilized SQUID magnetometry and Hall effect magnetometry to observe the properties of superconductor structures and superconductorferromagnetic mixed systems. We have used SQUID magnetometry and ferromagnetic resonance to observe the physical properties of ferromagnetic structures and the interactions between adjacent structures. Using these materials and methods we have discovered an unusual paramagnetic Meissner effect in thin Nb films that exists at igh-applied magnetic fields. We have discovered fluxoid matching anomalies at low sample temperature. And we have discovered interactions between electron exchange and magnetic dipole forces. Additionally, we have found clear evidence to support several past hypotheses advanced by other authors.
Watkins, Daniel Byron, "OBSERVED NONLINEAR RESPONSES IN PATTERNED SUPERCONDUCTING, FERROMAGNETIC, AND INTERACTING THIN FILMS" (2004). University of Kentucky Doctoral Dissertations. 425.