Nanoscale Texture and Microstructure in NdFeAs(O,F)/IBAD-MgO Superconducting Thin Film with Superior Critical Current Properties

Abstract

This paper reports the nanoscale texture and microstructure of a high-performance NdFeAs(O,F) superconducting thin film grown by molecular beam epitaxy on a textured MgO/Y${}_2$O${}_3$/Hastelloy substrate. The NdFeAs(O,F) film forms a highly textured columnar grain structure by epitaxial growth on the MgO template. Although the film contains stacking faults along the $ab$-plane as well as grain boundaries perpendicular to the $ab$-plane, good superconducting properties are measured: a critical temperature, $T_{\mathrm{c}}$, of 46 K and a self-field critical current density, $J_{\mathrm{c}}$, of $2\times 10^{6}A/c{\mathrm{m}}^2$ at 4.2 K. Automated crystal orientation mapping by scanning precession electron diffraction in transmission electron microscopy is employed to analyze the misorientation angles between adjacent grains in a large ensemble (247 grains). 99% of the grain boundaries show in-plane misorientation angles ($\Delta \gamma$) less than the critical angle ${\theta }_{\mathrm{c}}$, which satisfies one of the necessary conditions for the high $J_{\mathrm{c}}$. Comparing the columnar grain size distribution with the mean distance of the flux line lattice, the triple junctions of low-angle grain boundaries are found to be effective pinning centers, even at high temperatures ($\ge$35 K) and/or low magnetic fields.

Main text with Supplement Material, 32 pages, 16 figures

References in corpus (4)

• Advantageous grain boundaries in iron pnictide superconductors
• High-field transport properties of a P-doped BaFe2As2 film on technical substrate
• Intrinsic and extrinsic pinning in NdFeAs(O,F): vortex trapping and lock-in by the layered structure
• Highly textured oxypnictide superconducting thin films on metal substrates

Cited by in corpus (3)

• New scaling laws for pinning force density in superconductors
• Structural analysis and transport properties of [010]-tilt grain boundaries in Fe(Se,Te)
• Status of Iron Based Superconductors: characteristics and relevant properties for applications