High $J_{\mathrm{c}}$ and low anisotropy of hydrogen doped NdFeAsO superconducting thin film

Abstract

The recent realisations of hydrogen doped $Ln$FeAsO ($Ln$=Nd and Sm) superconducting epitaxial thin films call for further investigation of their structural and electrical transport properties. Here, we report on the microstructure of a NdFeAs(O,H) epitaxial thin film and its temperature, field, and orientation dependencies of the resistivity and the critical current density $J_{\mathrm{c}}$. The superconducting transition temperature $T_{\mathrm{c}}$ is comparable to NdFeAs(O,F). Transmission electron microscopy investigation supported that hydrogen is homogenously substituted for oxygen. A high self-field $J_{\mathrm{c}}$ of over 10 MA/cm${}^2$ was recorded at 5 K, which is likely to be caused by a short London penetration depth. The anisotropic Ginzburg-Landau scaling for the angle dependence of $J_{\mathrm{c}}$ yielded temperature-dependent scaling parameters ${\gamma }_{\mathrm{J}}$ that decreased from 1.6 at 30 K to 1.3 at 5 K. This is opposite to the behaviour of NdFeAs(O,F). Additionally, ${\gamma }_{\mathrm{J}}$ of NdFeAs(O,H) is smaller than that of NdFeAs(O,F). Our results indicate that heavily electron doping by means of hydrogen substitution for oxygen in $Ln$FeAsO is highly beneficial for achieving high $J_{\mathrm{c}}$ with low anisotropy without compromising $T_{\mathrm{c}}$, which is favourable for high-field magnet applications.

17 pages, 6 figures with Supplementary Information, accepted in Scientific Reports

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Cited by in corpus (1)

• High upper critical field (120 T) with small anisotropy of highly hydrogen-substituted SmFeAsO epitaxial film