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1. a -axis YBa ₂ Cu ₃ O _7−x /PrBa ₂ Cu ₃ O _7−x /YBa ₂ Cu ₃ O _7−x trilayers with subnanometer rms roughness

   https://doi.org/10.1063/5.0034648  

   Suyolcu, Y. Eren ; Sun, Jiaxin ; Goodge, Berit H. ; Park, Jisung ; Schubert, Jürgen ; Kourkoutis, Lena F. ; Schlom, Darrell G. ( February 2021 , APL Materials)
2. The benefit of Ca in improving pinning of BaZrO ₃ -Y ₂ O ₃ doubly-doped YBa ₂ Cu ₃ O _7-x /Ca _0.3 Y _0.7 Ba ₂ Cu ₃ O _7-x multilayer nanocomposite films

   https://doi.org/10.1088/2053-1591/acc7e3  

   Panth, Mohan ; Ogunjimi, Victor ; Sebastian, Mary Ann ; Gautam, Bibek ; Haugan, Timothy ; Wu, Judy ( April 2023 , Materials Research Express)

   Abstract This work examines the pinning enhancement in BaZrO 3 (BZO) +Y 2 O 3 doubly-doped (DD) YBa 2 Cu 3 O 7 (YBCO) nanocomposite multilayer (DD-ML) films. The film consists of two 10 nm thin Ca 0.3 Y 0.7 Ba 2 Cu 3 O 7-x (CaY-123) spacers stacking alternatively with three BZO + Y 2 O 3 /YBCO layers of 50 nm each in thickness that contain 3 vol% of Y 2 O 3 and BZO doping in the range of 2–6 vol%. Enhanced magnetic vortex pinning and improved pinning isotropy with respect to the orientation of magnetic field (B) have been achieved in the DD-ML samples at lower BZO doping as compared to that in the single-layer counterparts (DD-SL) without the CaY-123 spacers. For example, the pinning force density ( F p ) of ∼58 GNm −3 in 2 vol.% of DD-ML film is ∼110% higher than in 2 vol% of DD-SL at 65 K and B // c -axis, which is attributed to the improved pinning efficiency by c -axis aligned BZO nanorods through diffusion of Calcium (Ca) along the tensile-strained channels at BZO nanorods/YBCO interface for improvement of the interface microstructure and hence pinning efficiency ofmore »BZO nanorods. An additional benefit is in the considerably improved J c ( θ ) and reduced J c anisotropy in the former over the entire range of the B orientations. However, at higher BZO doping, the BZO nanorods become segmented and misoriented, which may change the Ca diffusion pathways and reduce the benefit of Ca in improving the pinning efficiency of BZO nanorods.« less
3. Enabling coherent BaZrO ₃ nanorods/YBa ₂ Cu ₃ O _7−x interface through dynamic lattice enlargement in vertical epitaxy of BaZrO ₃ /YBa ₂ Cu ₃ O _7−x nanocomposites

   https://doi.org/10.1088/1361-6668/ac4aff  

   Wu, Judy Z ; Ogunjimi, Victor ; Sebastian, Mary Ann ; Zhang, Di ; Jian, Jie ; Huang, Jijie ; Zhang, Yifan ; Gautam, Bibek ; Haugan, Timothy ; Wang, Haiyan ( February 2022 , Superconductor Science and Technology)

   Abstract One-dimensional c -axis-aligned BaZrO 3 (BZO) nanorods are regarded as strong one-dimensional artificial pinning centers (1D-APCs) in BZO-doped YaBa 2 Cu 3 O 7− x (BZO/YBCO) nanocomposite films. However, a microstructure analysis has revealed a defective, oxygen-deficient YBCO column around the BZO 1D-APCs due to the large lattice mismatch of ∼7.7% between the BZO (3a = 1.26 nm) and YBCO (c = 1.17 nm), which has been blamed for the reduced pinning efficiency of BZO 1D-APCs. Herein, we report a dynamic lattice enlargement approach on the tensile strained YBCO lattice during the BZO 1D-APCs growth to induce c -axis elongation of the YBCO lattice up to 1.26 nm near the BZO 1D-APC/YBCO interface via Ca/Cu substitution on single Cu-O planes of YBCO, which prevents the interfacial defect formation by reducing the BZO/YBCO lattice mismatch to ∼1.4%. Specifically, this is achieved by inserting thin Ca 0.3 Y 0.7 Ba 2 Cu 3 O 7− x (CaY-123) spacers as the Ca reservoir in 2–6 vol.% BZO/YBCO nanocomposite multilayer (ML) films. A defect-free, coherent BZO 1D-APC/YBCO interface is confirmed in transmission electron microscopy and elemental distribution analyses. Excitingly, up to five-fold enhancement of J c ( B ) at magnetic field Bmore »= 9.0 T// c -axis and 65 K–77 K was obtained in the ML samples as compared to their BZO/YBCO single-layer (SL) counterpart’s. This has led to a record high pinning force density F p together with significantly enhanced B max at which F p reaches its maximum value F p,max for BZO 1D-APCs at B // c -axis. At 65 K, the F p,max ∼158 GN m −3 and B max ∼ 8.0 T for the 6% BZO/YBCO ML samples represent a significant enhancement over F p,max ∼ 36.1 GN m −3 and B max ∼ 5.0 T for the 6% BZO/YBCO SL counterparts. This result not only illustrates the critical importance of a coherent BZO 1D-APC/YBCO interface in the pinning efficiency, but also provides a facile scheme to achieve such an interface to restore the pristine pinning efficiency of the BZO 1D-APCs.« less
4. Probing the effect of interface on vortex pinning efficiency of one-dimensional BaZrO ₃ and BaHfO ₃ artificial pinning centers in YBa ₂ Cu ₃ O _7-x thin films

   https://doi.org/10.1063/1.5050616  

   Gautam, Bibek ; Sebastian, Mary Ann ; Chen, Shihong ; Misra, Shikhar ; Huang, Jijie ; Javier Baca, F. ; Emergo, Rose ; Haugan, Timothy ; Xing, Zhongwen ; Wang, Haiyan ; et al ( November 2018 , Applied Physics Letters)
5. The angular range of effective pinning by one-dimensional artificial pinning centers in BaZrO ₃ /YBa ₂ Cu ₃ O _7-x nanocomposite films

   https://doi.org/10.1063/1.5097703  

   Ogunjimi, Victor ; Gautam, Bibek ; Sebastian, Mary Ann ; Haugan, Timothy ; Wu, Judy ( August 2019 , AIP Advances)