Structural, electro-magnetic, and optical properties of Ba(Fe,Ni)2As2 single-crystal thin film

Abstract

We investigated the superconducting transition temperature (T c), critical current density (J c) and optical properties of optimally doped Ba(Fe0.95Ni0.05)2As2 (Ni-Ba122) single-crystalline epitaxial thin films grown by pulsed laser deposition for the first time. The T c at zero resistivity was about 20.5 K and the J c at self-field and 4.2 K was 2.8 MA cm-2 calculated by the Bean model. The superconducting properties such as T c and J c of thin films are comparable to those of bulk single-crystal samples. The superfluid plasma frequency (λ p,S) of Ni-Ba122 thin film is ∼7033 cm-1 obtained by optical spectroscopic technique. Based on this plasma frequency, we obtained the London penetration depth (λ L), ∼226 nm at 8 K, which is comparable to those of optimally Co- and K-doped BaFe2As2 single crystals. © 2016 IOP Publishing Ltd.