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Interfacial engineering via nanoparticle substrate surface decoration has been extended to coated conductor templates. Preformed BaTiO3 and BaZrO3 nanoparticles were applied to substrate surfaces, prior to YBa2Cu3O7-δ (YBCO) deposition, by using a scalable and inexpensive technique of solution-based suspension. Compared to untreated reference samples, nanodecoration yields improved in-field critical current density (Jc) as well as strong correlated pinning along the c-axis direction of the YBCO film. Accordingly, a much reduced falloff of Jc with magnetic field strength was observed in all of the modified samples. In addition, scaling behavior of the normalized volume pinning force density (Fp) with respect to temperature provided insight as to the differences in flux pinning mechanisms dependent on the decoration technique. Finally, with these results our earlier proof-of-concept demonstrations on nanoparticle modified single crystal substrates were replicated on technological substrates, pointing to the versatility of this simple technique for realization of enhanced high temperature superconductor performance. [ABSTRACT FROM AUTHOR]

We have acquired positive results in a controlled study to investigate the effects of substrate surface modification on the growth-induced flux-pinning nanostructures in YBa2Cu3O7-δ (YBCO) films. Nanoscale iridium (Ir) particles were applied to single-crystal SrTiO3 substrate surfaces using dc-magnetron sputtering. Superconducting properties of YBCO films grown on the Ir-modified substrates, measured by transport and magneto-optical imaging, have shown substantial improvement in the critical current densities (Jc) at 77 K over those on untreated, control substrates. Results also show a nearly uniform enhancement of Jc over all orientations of magnetic field. Present results are found to be consistent with cross-sectional transmission electron microscopy investigations. Ultimately, the objective of this approach is to produce enhancements in the properties of coated conductors by a simple pretreatment of the substrate surface. [ABSTRACT FROM AUTHOR]

The ion implantation of nearly equal doses of Co and Pt into a single-crystal Al2O3 host followed by thermal annealing leads to the formation of nanoparticles whose phase, structure, and physical properties are strongly dependent on the annealing environment. Annealing in 96%Ar+4%H2 gives rise to ferromagnetic, chemically ordered CoPt nanoparticles with the L10 structure and a magnetic coercivity that can exceed 10 kOe at 5 K. Annealing in O2 (or in Ar) does not result in the formation of a CoPt alloy. Instead, the implanted Pt precipitates to form oriented elemental Pt nanoparticles, and the implanted Co combines with oxygen to form Co3O4 oxide nanoparticles. Annealing in ultrahigh-vacuum conditions results in a mixture of phases including CoPt3 and Co3O4 and possibly Co. The results obtained for Co+Pt-implanted Al2O3 are compared with the previous results for Fe+Pt-implanted Al2O3 annealed in similar environments. [ABSTRACT FROM AUTHOR]

The properties of FePt nanoparticles formed by the implantation of Fe+Pt into c-axis-oriented Al2O3 single crystals followed by thermal annealing are shown to be strongly dependent on the annealing environment. Annealing in a reducing environment (flowing Ar+4% H2, or ultrahigh vacuum) gives rise to ferromagnetic FePt nanoparticles with the L10 structure and very high magnetic coercivity (greater than 20 kOe). FePt alloy formation does not occur during annealing in an oxidizing environment. Instead, the implanted Pt precipitates out forming oriented Pt nanoparticles and the implanted Fe redistributes with ∼40% segregating to the surface where it forms epitaxial α-Fe2O3 precipitates at the surface; the remainder of the implanted Fe remains in the bulk, most likely in solid solution in the matrix. Results obtained by sequential annealing of Fe+Pt implanted samples in reducing (oxidizing) environments followed by annealing in an oxidizing (reducing) environment suggest that equilibrium, rather than kinetic, effects are responsible for the observed microstructures. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Oriented Fe[sub 1-x]Pt[sub x] nanoparticles have been formed in single-crystal Al[sub 2]O[sub 3] host matrices by the sequential implantation of Fe and Pt ions followed by thermal annealing. For x in the range of ∼35–55 at. % Pt, these nanoparticles are in the chemically ordered tetragonal L1[sub 0] structure of FePt and appear to be fully ordered. The nanoparticles are ferromagnetic, and the magnetic coercivity is a strong function of the alloy composition, reaching values in excess of 20 kOe for x∼45%. The crystallographic orientation and morphology of the nanoparticles are strongly dependent on the implantation conditions. Under certain implantation conditions, a buried amorphous layer can be formed in the Al[sub 2]O[sub 3] matrix which crystallizes during annealing giving rise to the formation of an interconnected network of large FePt particles with a single orientation. Oriented nanoparticles of Fe[sub 3]Pt and FePt[sub 3] were also synthesized. The Fe[sub 3]Pt and FePt[sub 3] particles have the ordered, cubic L1[sub 2] structure with an order parameter of 0.5–0.8; and these particles also exhibit ferromagnetic behavior. The magnetic and structural properties of the Fe[sub 1-x]Pt[sub x] nanoparticles are compared to and contrasted with those of nanoparticles of Fe and Pt in Al[sub 2]O[sub 3] that were also formed by ion-beam synthesis. Evidence for Al incorporation into the nanoparticles is also presented. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Magnetic force microscopy (MFM) has been used to investigate the properties of ferromagnetic FePt nanoparticles produced by the implantation of Fe and Pt ions into single-crystal A1[SUB2]O[SUB3] or fused SiO[SUB2] followed by thermal processing. The MFM results are compared to cross-section and plan view transmission electron microscopy images of the same samples. We demonstrate that MFM can detect magnetism in nanosized particles that are situated several hundred nm below the sample surface. MFM is shown to be a promising tool for studying the characteristics of magnetic nanoparticles produced by ion implantation. [ABSTRACT FROM AUTHOR]