Saturday, 3G-02, 11:50-11:55

BaZrO₃ nanorod realignment in YBa₂Cu₃O_7-x thin films by surface modulation using vicinal SrTiO₃ substrates

F. J. Baca

T. J. Haugan, J. N. Reichart, and P. N. Barnes

Air Force Research Laboratories, Propulsion Directorate, 1950 Fifth St., WPAFB, OH 45433
Phone: (937) 255-6940, Fax: (937) 255- 4307, Francisco.Baca@wpafb.af.mil

R. L. Emergo, and J. Z. Wu

University of Kansas, Department of Physics and Astronomy, 1251 Wescoe Hall Dr., Lawrence, KS, 66045

The self-assembled columnar defects formed by BaZrO₃ and BaSnO₃ nanorods in YBa₂Cu₃O_7-x thin films provide effective vortex pinning, especially for magnetic fields aligned along the c-axis. However, to improve vortex pinning for other field orientations, it is desirable to control the defect orientation. Using transmission electron microscopy, we show that by increasing the vicinal angle of miscut SrTiO₃ substrates, the microstructural effect on BaZrO₃-doped YBCO films becomes increasingly pronounced. We show that planar defects become more prominent up to a 10° vicinal angle, while at 20° the BaZrO₃ nanorods undergo a drastic reorientation and become aligned parallel to the YBCO a-b planes. The angular dependence of the in-field critical current density, J_c(H, Θ), confirms that as the vicinal angle is increased, the vortex pinning along the c-axis is reduced, while it is increased slightly along the a-b direction. Since the alignment of microstructural dislocations is considered to play a significant role in the formation of nanocolumnar defects, these results may indicate that the miscut angle strongly influences the occurrence of such dislocations, and hence, the direction of the BaZrO₃ nanorod alignment when a critical angle is exceeded.

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