Di Zhang

One-dimensional artificial pinning centers (1D-APCs) in YBa 2 Cu 3 O 7-x nanocomposite films provide strong collective pinning at magnetic field B//c-axis. In this work, we reveal a 1D-APC/YBa 2 Cu 3 O 7-x interface is preferred for high pinning efficiency of individual 1D-APCs including BaHfO 3 and BaZrO 3 . The coherent 1D-APC/YBa 2 Cu 3 O 7-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 (J c ) 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 …

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The coexistence of nonvolatile and volatile switching modes in a single memristive device provides flexibility to emulate both neuronal and synaptic functions in the brain. Furthermore, such a device structure may eliminate the need for additional circuit elements such as transistor-based selectors, enabling low-power consumption and high-density device integration in fully memristive spiking neural networks. In this work, we report dual resistive switching (RS) modes in VO2/La0.7Sr0.3MnO3 (LSMO) bilayer memristive devices. Specifically, the nonvolatile RS is driven by the movement of oxygen vacancies (Vo) at the VO2/LSMO interface and requires a higher biasing voltage, whereas the volatile RS is controlled by the metal–insulator transition (MIT) of VO2 under a lower biasing voltage. The simple device structure is electrically driven between the two RS modes and thus can operate as a one selector–one …

Nanostructured plasmonic–magnetic metamaterials have gained great research interest due to their enhanced magneto-optical coupling effects. Here, we report a complex three-phase nanocomposite design combining ferromagnetic CoFe2 with plasmonic TiN and Au as a multifunctional hybrid metamaterial using either a cogrowth or a templated method. Via the first method of cogrowing three phases, three different morphologies of Au–CoFe2 core–shell nanopillars were formed in the TiN matrix. Via the second method of sequential deposition of a TiN–Au seed layer and a TiN–CoFe2 layer, highly ordered and uniform single-type core–shell nanopillars (i.e., the CoFe2 shell with a Au core) form in the TiN matrix. Both cogrowth and templated growth TiN–CoFe2–Au hybrid systems exhibit excellent epitaxial quality, hyperbolic dispersion, magnetic anisotropy, and a magneto-optical coupling effect. This study …

Phase separation in manganites leads to unique magnetic and electronic properties. 50% Ca‐doped LaMnO3 (LCMO), at the boundary of ferromagnetic (FM) and antiferromagnetic (AFM) states in La1‐xCaxMnO3 (0 ≤ x ≤ 1), is an ideal system to study phase separation behavior. The investigation reveals the effect of a 5d‐metal perovskite SrIrO3 (SIO) on the phase separation, magnetic, and magnetoresistance (MR) properties of LCMO. Single‐layer and bilayer LCMO films, both appear purely ferromagnetic along the in‐plane (IP) magnetic field direction, but show the tendency of temperature‐dependent ferromagnetic and antiferromagnetic or charge‐ordered (CO) phase separation with the out‐of‐plane (OOP) applied field. The MR, and colossal magnetoresistance (CMR), observed in LCMO/SIO bilayers are two orders and an order of magnitude (in %) larger, respectively than that in the single‐layer film. The …

An important research goal in the applications of high temperature superconductor YBa 2 Cu 3 O 7-δ (YBCO) thin films is increasing both the critical current density and also the isotropic nature of the film. YBCO is inherently anisotropic due to its layered perovskite structure. The critical current density of YBCO thin films is enhanced by increasing the flux pinning sites in the film by the addition of insulating nano-phase materials, such as BaZrO 3 (BZO) nanorods, which are also anisotropic in nature. Using a multilayer pulsed laser deposition technique has been shown to produce films with inclusions that are more isotropic in nature. However, the defective BZO nanorod interface, resulting from its lattice mismatch with YBCO, prevents obtaining optimum pinning force. This research explores the effect of Ca doped YBCO space layers in the multilayer composite film, on the BZO nanorod/YBCO interface, over a wide …

Metamaterials have gained great research interest in recent years owing to their potential for property tunability, multifunctionality, and property coupling. As a new group of self‐assembled thin films, vertically aligned nanocomposite (VAN)‐based hybrid metamaterials have been demonstrated with significant anisotropic physical properties and a broad range of property tailorability, such as optical anisotropy, magnetic anisotropy, hyperbolic dispersion, and enhanced second harmonic generation properties. Herein, self‐assembled ZrO2‐Co nanocomposite films, with high epitaxial quality and ultra‐fine vertically aligned Co nanopillars (with an average diameter of ≈2 nm) embedded in a ZrO2 matrix, are fabricated using a pulsed laser deposition (PLD) method. The Co pillar density can be effectively tuned by varying the Co concentration in the target, which results in tunable optical properties and magnetic …

As the energy demand is expected to double over the next 30 years, there has been a major initiative towards advancing the technology of both energy harvesting and storage for renewable energy. In this work, we explore a subset class of dielectrics for energy storage since ferroelectrics offer a unique combination of characteristics needed for energy storage devices. We investigate ferroelectric lead-free 0.5[Ba(Ti0.8Zr0.2)O3]-0.5(Ba0.7Ca0.3)TiO3 epitaxial thin films with different crystallographic orientations grown by pulsed laser deposition. We focus our attention on the influence of the crystallographic orientation on the microstructure, ferroelectric, and dielectric properties. Our results indicate an enhancement of the polarization and strong anisotropy in the dielectric response for the (001)-oriented film. The enhanced ferroelectric, energy storage, and dielectric properties of the (001)-oriented film is explained by the coexistence of orthorhombic-tetragonal phase, where the disordered local structure is in its free energy minimum.