Structure and flux pinning properties of irradiation defects in YBa sub 2 Cu sub 3 O sub 7-x Page: 10 of 25
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compared with one of the leading computer model codes for ion irradiation
of materials (TRIM1), where some difference was noted. Of special
interest is the damaging mechanism, which is based on the transfer of ion
energy into the material electronic system, primarily by ionization. The
efficiency of transfer of this locally deposited energy from electron
ionization into the atomic structure, locally disordering this structure,
nust be quite high. It is the atomic disorder which is imaged in TEM.
These nearly linear, somewhat discontinuous tracks of atomic disorder
are very effective pinners of magnetic flux vortices, especially at higher
temperatures and fields.
SUMMARY
By combining observations by TEM and measurements of magnetization in
single crystals of YBCO irradiated with neutrons, protons and electrons,
we have made progress in determining the structure and flux pinning
properties of various irradiation defects. Contributions to pinning of
magnetic flux vortices by defect cascades in neutron irradiated samples,
and by point defect processes under all irradiation conditions have been
investigated by irradiation and annealing experiments. The displacement
of copper atoms from the CuO2 planes has been determined to produce
significant pinning defects under electron irradiations, and by inference
also under proton and neutron irradiations. Unusual pinning anisotropies
have been found in all irradiation conditions. The influence of existing
preirradiation pinning defects on both Jc enhancements and shifts in the
reversible field values upon irradiation is demonstrated in eight different
single crystals. A brief discussion of recent TEM results on linear defect
tracks produced by 580 MeV Sn ion irradiation is given.
ACKNOWLEDGEMENTS
It is a pleasure to thank and acknowledge the efforts of Marcus Frischherz
(ANL and Atominstitute, Vienna), Beatrix Vlcek (ANL), Hema Viswanathan
(ANL and Purdue University), John Giapintzakis (University of Illinois), Bob
Wheeler (ANL), and James Gledhill (University of Oxford, U.K.), who
obtained most of the data. I also wish to thank my collaborators Harald
Weber (Atominstitute, Vienna), Leonardo Civale and Alan Marwick (IBM),
Don Ginsberg (University of Illinois), Marie-Odile Ruault (University of
Paris, Orsay), Mike Jenkins (University of Oxford, U.K.), and George
Crabtree (ANL) for much support and good advice. This work was
supported by the U. S. Department of Energy, Conservation and Renewable
Energy, and Basic Energy Sciences-Materials-Science, under Contract No.
W-31-109-ENG-38, the National Science Foundation-Office of Science and
Technology Center for Superconductivity, under Contract No. STC-9
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Kirk, M.A. Structure and flux pinning properties of irradiation defects in YBa sub 2 Cu sub 3 O sub 7-x, article, June 1, 1992; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1058223/m1/10/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.