Final Technical Report Grant No. DE-FG02-97ER45653 Lance E. De Long, Principal Investigator, University of Kentucky Period of Performance: 09/01/97 to 05/14/15

Technical Report · Thu Nov 24 00:00:00 EST 2016

DOI:https://doi.org/10.2172/1333312· OSTI ID:1333312

De Long, Lance Eric ^[1]

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1. Univ. of Kentucky, Lexington, KY (United States)

Prior to 1997, the PI had studied the unusual upper critical magnetic field phase boundaries of several novel or exotic types of superconductors, including charge density wave materials such as NbSe₂, organic superconductors such as κ-(ET)₂Cu[N(CN)₂]Br, high-temperature oxide superconductors such as (Ba,K)BiO₃ and the cuprates, heavy fermion superconductors such as U₆Fe, UBe₁₃, URu₂Si₂ and UPt₃, and re-entrant Kondo alloys such as (La,Ce)Al₂ and ferromagnetic superconductors such as ErRh₄B₄. Most of these materials exhibited marked positive or negative curvature of H_C2(T) which could not be explained by traditional pair-breaking models. It became clear that many of these materials had very short coherence lengths that made quantized vortices highly mobile (depinned) near the phase boundary, and the fundamental, equilibrium H_C2(T) difficult to measure using finite field or current drives. These problems made the underlying physics obscure, and led to erroneous interpretations of experimental data in terms of models of exotic superconducting pairing mechanisms. Around 1995, these issues led the PI to take advantage of modern electron beam lithography techniques for patterning superconducting and ferromagnetic thin films on the nanoscale. Primarily due to strong magnetic shape anisotropy effects, EBL patterning has led to enhanced control of the spatial distribution and dynamics of topological defects such as domain walls and magnetic vortices, which can create serious energy dissipation and other limitations for modern devices. Moreover, finite size and interface effects also strongly alter phase transition temperatures and phase boundaries of superconducting and magnetic films, as well as introduce barriers to equilibration, enhanced fluctuations and alter magnetic relaxation. Geometrical frustration and spin ice behavior can also be systematically controlled in patterned film media. Film patterning thus provides an excellent tool for conducting highly-controlled, fundamental studies of cooperative phases and interactions in artificially structured condensed matter.

• Research Organization: Univ. of Kentucky, Lexington, KY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: FG02-97ER45653
• OSTI ID: 1333312
• Report Number(s): DE-FG02-97ER45653; TRN: US1700758
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SUPERCONDUCTORS
THIN FILMS
KENTUCKY
OXIDES
ELECTRON BEAMS
COHERENCE LENGTH
TRANSITION TEMPERATURE
PHASE TRANSFORMATIONS
SPATIAL DISTRIBUTION
FLUCTUATIONS
SPIN
TOPOLOGY
MAGNETIC FIELDS
MAGNETIC FLUX
ANISOTROPY
CONTROL
CRYSTAL DEFECTS
ICE
INTERFACES
NANOSTRUCTURES
RELAXATION
SHAPE
VORTICES
TRANSITION ELEMENT COMPOUNDS
DOMAIN STRUCTURE
PHASE STUDIES
RESEARCH PROGRAMS
FERROMAGNETIC MATERIALS
DYNAMICS
METAMATERIALS