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One-dimensional artificial pinning centers (1D-APCs) in YBa2Cu3O7-x nanocomposite films provide strong collective pinning at magnetic field B//c-axis. In this work, we reveal a 1D-APC/YBa2Cu3O7-x interface is preferred for high pinning efficiency of individual 1D-APCs including BaHfO3 and BaZrO3. The coherent 1D-APC/YBa2Cu3O7-x interface may be obtained via either growth of the nanocomposite films at optimal condition or Ca-diffusion to dynamically reduce the interface strain during the nanocomposite film growth. Interestingly, the high pinning efficiency of the 1D-APCs with coherent interfaces with YBCO not only lead to a high critical current density (Jc) in magnetic fields up to 9.0 T at H//c-axis but also enhanced Jc over a larger angular range when H is away from H//c-axis up to θ=60-80 degree than that in the case the interface is defective. This result suggests the importance of understanding and engineering the APC/YBCO interface for optimal pinning in nanocomposite films. 

Abstract Vertically aligned nanocomposite (VAN) thin films offer exceptional physical properties through diverse material combinations, providing a robust platform for designing complex nanocomposites with tailored performance. Considering materials compatibility issues, most of oxide‐metal VANs have focused on noble metals as the secondary phase in the oxide matrix. Here, an oxide‐metal hybrid metamaterials in the VAN form has been designed which combines ferroelectric BaTiO₃(BTO) with two immiscible non‐noble metal elements of Co and Cu, resulting in a three‐phase BTO‐Co‐Cu (BTO‐CC) VAN film. This film exhibits a characteristic nanopillar‐in‐matrix nanostructure with three distinct types of nanopillar morphologies, i.e., Co‐rich cylindrical nanopillars, Cu‐Co‐nanolaminated Co rectangular nanopillars and Co‐Cu‐core–shell cylindrical nanopillars. Phase field modeling indicates the constructed structure is resulted from the interplay between thermochemical, chemomechanical, and interfacial energy driving forces. The strong structural anisotropy leads to anisotropic optical and magnetic properties, presenting potential as hyperbolic metamaterial (HMM) with transverse‐positive dispersion in the near‐infrared region. The inclusion of non‐noble Cu nanostructure induces surface plasmon resonance (SPR) in the visible region. Additionally, ferroelectric properties have been demonstrated in a BTO/BTO‐CC bilayer, confirming room‐temperature multiferroicity in the film. The complex three‐phase VANs offer a novel platform for exploring electro‐magneto‐optical coupling along vertical interfaces toward future integrated devices. 

Abstract Microstructural analysis of the BaZrO 3 (BZO)/YBa 2 Cu 3 O 7 (YBCO) interface has revealed a highly defective and oxygen deficient 2-3 nm thick YBCO column surrounding the BZO one-dimensional artificial pinning centers (1D-APCs). The resulting semi-coherent interface is the consequence of the ∼7.7% BZO/YBCO lattice mismatch and is responsible for the low pinning efficiency of BZO 1D-APCs. Herein, we report an interface engineering approach of dynamic Ca/Cu replacement on YBCO lattice to reduce/eliminate the BZO/YBCO lattice mismatch for improved pinning at a wide angular range of the magnetic field orientation. The Ca/Cu replacement induces a local elongation of the YBCO c-lattice near the BZO/YBCO interface, thereby ensuring a reduction in the BZO/YBCO lattice mismatch to ∼1.4% and a coherent BZO/YBCO interface. This has resulted in enhanced pinning at B//c-axis and a broad angular range of B-field orientation. For example, the 6 vol.% BZO/YBCO film with interface engineering exhibits F p ∼158 GN/m 3 at 65 K and B//c-axis, which is 440% higher than the ∼36.1 GN/m 3 for the reference 6% BZO/YBCO sample, and enhanced J c and F p in a wide angular range up to ∼ 80°. This result illustrates a facile scheme for engineering 1D-APC/YBCO interface to resume the pristine pinning efficiency of the 1D-APCs.