论文标题
实现超导体K-doped bafe $ _ \ text {2} $的外延薄膜$ _ \ text {2} $
Realization of epitaxial thin films of the superconductor K-doped BaFe$_\text{2}$As$_\text{2}$
论文作者
论文摘要
基于铁的超导体ba $ _ {1-x} $ k $ _x $ _x $ fe $ _ \ text {2} $作为$ _ \ text {2} $作为高磁场应用程序的关键材料，这是由于超导电线和块状永久磁铁的最新发展而成为高磁场应用。外延薄膜在研究和人为调整物理特性中起着重要作用。尽管如此，ba $ _ {1-x} $ k $ _x $ fe $ _2 $的合成为$ _2 $，由于K。 ba $ _ {1-x} $ k $ _x $ _x $ fe $ _ \ text {2} $作为$ _ \ text {2} $薄膜由分子束外观上的薄膜，使用氟化物底物组合（caf $ _ \ _ \ text {2} $，srf $ _，srf $ _ \ text $ _ \ text $ _ \ text Text} BAF $ _ \ text {2} $）和低增长温度（350 $ - $ 420 $^\ circ $ c）。我们在Caf $ _ \ text {2} $上生长的外延薄膜在临界温度的发作临界温度下显示出尖锐的超导过渡，略低于散装晶体，略低于大约2 K，这可能是由于晶格和热膨胀不匹配引起的应变效应。由磁化磁滞回路确定的临界电流密度（$ j $$ _ \ text {c} $）高达2.2 ma/cm $^\ text {2} $在自我场下4 K时。胶片的内场$ j $$ _ \ text {c} $的特征优于散装晶体。外延薄膜的实现为通过外延菌株和揭示Ba $ _ {1-x} $ K $ _x $ _x $ _x $ fe $ _ \ text {2} $作为$ _ \ text {2} $的内在晶粒边界运输开辟了机会，并揭示了ba $ _ {1-x} $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _x $ _ \ text {2} $。
The iron-based superconductor Ba$_{1-x}$K$_x$Fe$_\text{2}$As$_\text{2}$ is emerging as a key material for high magnetic field applications owing to the recent developments in superconducting wires and bulk permanent magnets. Epitaxial thin films play important roles in investigating and artificially tuning physical properties; nevertheless, the synthesis of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ epitaxial thin films remained challenging because of the high volatility of K. Herein, we report the successful growth of epitaxial Ba$_{1-x}$K$_x$Fe$_\text{2}$As$_\text{2}$ thin films by molecular-beam epitaxy with employing a combination of fluoride substrates (CaF$_\text{2}$, SrF$_\text{2}$, and BaF$_\text{2}$) and a low growth temperature (350$-$420$^\circ$C). Our epitaxial thin film grown on CaF$_\text{2}$ showed sharp superconducting transition at an onset critical temperature of 36 K, slightly lower than bulk crystals by ~2 K due presumably to the strain effect arising from the lattice and thermal expansion mismatch. Critical current density ($J$$_\text{c}$) determined by the magnetization hysteresis loop is as high as 2.2 MA/cm$^\text{2}$ at 4 K under self-field. In-field $J$$_\text{c}$ characteristics of the film are superior to the bulk crystals. The realization of epitaxial thin films opens opportunities for tuning superconducting properties by epitaxial strain and revealing intrinsic grain boundary transport of Ba$_{1-x}$K$_x$Fe$_\text{2}$As$_\text{2}$.
