Iida Kazumasa, Hänisch Jens, Kondo Keisuke, Chen Mingyu, Hatano Takafumi, Wang Chao, Saito Hikaru, Hata Satoshi, Ikuta Hiroshi
Department of Materials Physics, Nagoya University, Chikusa-ku, Nagoya, 464-8603, Japan.
JST CREST, Kawaguchi, Saitama, 332-0012, Japan.
Sci Rep. 2021 Mar 11;11(1):5636. doi: 10.1038/s41598-021-85216-3.
The recent realisations of hydrogen doped LnFeAsO (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. The superconducting transition temperature T is comparable to NdFeAs(O,F). Transmission electron microscopy investigation supported that hydrogen is homogenously substituted for oxygen. A high self-field J of over 10 MA/cm 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 yielded temperature-dependent scaling parameters γ 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, γ 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 LnFeAsO is highly beneficial for achieving high J with low anisotropy without compromising T, which is favourable for high-field magnet applications.
近期实现的氢掺杂LnFeAsO（Ln = Nd和Sm）超导外延薄膜，需要对其结构和电输运性质进行进一步研究。在此，我们报道了NdFeAs(O,H)外延薄膜的微观结构及其电阻率和临界电流密度J随温度、磁场和取向的变化关系。超导转变温度T与NdFeAs(O,F)相当。透射电子显微镜研究表明，氢均匀地替代了氧。在5 K时记录到超过10 MA/cm的高自场J，这可能是由较短的伦敦穿透深度引起的。J的角度依赖性的各向异性金兹堡 - 朗道标度给出了随温度变化的标度参数γ，其从30 K时的1.6降至5 K时的1.3。这与NdFeAs(O,F)的行为相反。此外，NdFeAs(O,H)的γ小于NdFeAs(O,F)的γ。我们的结果表明，通过用氢替代LnFeAsO中的氧进行重电子掺杂，对于在不降低T的情况下实现低各向异性的高J非常有利，这对高场磁体应用是有利的。
