More Like this

1. Polarization pinning at antiphase boundaries in multiferroic YbFeO ₃

   https://doi.org/10.1088/1674-1056/ad8cbc  

   Ren, Guodong; Omprakash, Pravan; Li, Xin; Yun, Yu; Thind, Arashdeep S; Xu, Xiaoshan; Mishra, Rohan (November 2024, Chinese Physics B)

   Abstract The switching characteristics of ferroelectrics and multiferroics are influenced by the interaction of topological defects with domain walls. We report on the pinning of polarization due to antiphase boundaries in thin films of the multiferroic hexagonal YbFeO₃. We have directly resolved the atomic structure of a sharp antiphase boundary (APB) in YbFeO₃thin films using a combination of aberration-corrected scanning transmission electron microscopy (STEM) and total energy calculations based on density-functional theory (DFT). We find the presence of a layer of FeO₆octahedra at the APB that bridges the adjacent domains. STEM imaging shows a reversal in the direction of polarization on moving across the APB, which DFT calculations confirm is structural in nature as the polarization reversal reduces the distortion of the FeO₆octahedral layer at the APB. Such APBs in hexagonal perovskites are expected to serve as domain-wall pinning sites and hinder ferroelectric switching of the domains. 

   more » « less
2. 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)
3. The effect of APC/YBCO interface on the angular range of effective pinning by one-dimensional artificial pinning centers in YBa ₂ Cu ₃ O _7-x nanocomposite films

   https://doi.org/10.1088/1757-899X/756/1/012025  

   Ogunjimi, V; Gautam, B; Sebastian, M.A.; Haugan, T; Wu, J (March 2020, IOP Conference Series: Materials Science and Engineering)
4. Superconducting HfO ₂ -added solution-derived YBa ₂ Cu ₃ O ₇ nanocomposite films: the effect of colloidal nanocrystal shape and crystallinity on pinning mechanism

   https://doi.org/10.1088/1361-6668/ac7ae3  

   Rijckaert, H; Malmivirta, M; Banerjee, S; Billinge, S J; Huhtinen, H; Paturi, P; De Buysser, K; Van Driessche, I (June 2022, Superconductor Science and Technology)

   Abstract Two different types of monoclinic HfO 2 nanocrystals were employed in this work to study the effect of nanocrystal shape and crystallinity on the structural defects in the YBa2Cu3O7−δ (YBCO) matrix as it leads to an enhancement of pinning performances of solution-derived YBCO nanocomposite films. In this work the nanorod-like HfO 2 nanocrystals obtained from surfactant-controlled synthesis led to short intergrowths surrounding the particles, while spherical HfO 2 nanocrystals from the solvent-controlled synthesis led to the formation of long stacking faults in the YBCO matrix. It means that the small difference in crystallinity, lattice parameters, nanocrystal structures, core diameter of preformed nanocrystals in colloidal solutions have a strong influence on the formation of the structural defects around the particles in the YBCO matrix, leading to different pinning performances. 

   more » « less
5. Enhancing magnetic pinning by BaZrO ₃ nanorods forming coherent interface by strain-directed Ca-doping in YBa ₂ Cu ₃ O _7−x nanocomposite films

   https://doi.org/10.1088/1361-6668/ac1fd3  

   Ogunjimi, Victor; Sebastian, Mary Ann; Zhang, Di; Gautam, Bibek; Jian, Jie; Huang, Jijie; Zhang, Yifan; Haugan, Timothy; Wang, Haiyan; Wu, Judy (September 2021, Superconductor Science and Technology)

   Abstract BaZrO₃(BZO) one-dimensional artificial pinning centers (1D-APCs) aligned along thec-axis of the YBa₂Cu₃O₇(YBCO) have been adopted to enhance the magnetic vortex pinning in BZO/YBCO nanocomposite films. However, the pinning force densityF_pof the BZO 1D-APCs remains moderate at temperatures near 77 K. A hypothesis of the major limiting factor is the defective BZO 1D-APCs/YBCO interface as a direct consequence of the large interfacial strain originated from the BZO/YBCO lattice mismatch of ∼7.7%. Herein, we explore enlarging thec-axis of the YBCO dynamically to reduce the lattice mismatch and hence to prevent formation of the defective BZO 1D-APCs/YBCO interface. Specifically, thec-axis enlargement was achieved by partial replacement of Cu with Ca on the YBCO lattice using strain-directed Ca diffusion into YBCO from two Ca_0.3Y_0.7Ba₂Cu₃O_7−x(CaY-123) spacers of only 10 nm in thickness inserted into the 2 vol% BZO 1D-APC/YBCO nanocomposite thin films of ∼150 nm in total thickness. The achieved elongatedc-axis is attributed to the formation of stacking faults induced by Ca-replacement of Cu on YBCO lattice. The reduced BZO/YBCO lattice mismatch allows formation of a coherent BZO 1D-APC/YBCO interface with negligible defects. This leads to an enhancedF_pvalue up to 98 GN m⁻³at 65 K, which is 70% higher than that of the reference 2 vol% BZO 1D-APC/YBCO sample. Furthermore, the benefit of the enhanced pinning of the BZO 1D-APCs with a coherent interface with YBCO can be extended to a large angular range of the magnetic field orientation. This study reveals the significant effect of the BZO/YBCO interface on the pinning efficiency of BZO 1D-APCs and provides a promising approach to achieve a coherent interface in BZO/YBCO nanocomposite films. 

   more » « less