High critical current density over 1 MA cm^−2 at 13 T in BaZrO₃ incorporated Ba(Fe,Co)₂As₂ thin film

다국어 초록 (Multilingual Abstract)

<P>Achieving high critical current density (<I>J</I> <SUB>c</SUB>) under a high magnetic field in Fe based superconductors is indispensable for practical applications. Here we report that high critical current density over 1 MA cm<SUP>−2</SUP> in high field (13 T) can be achieved in BaZrO<SUB>3</SUB> (BZO) incorporated Ba(Fe,Co)<SUB>2</SUB>As<SUB>2</SUB> (Co-Ba122) thin film grown on CaF<SUB>2</SUB> substrate using pulsed laser deposition. The magnetization <I>J</I> <SUB>c</SUB> of Co-Ba122 thin film incorporated with 2 mol.% BZO reaches 1.3 MA cm<SUP>−2</SUP> (<I>H</I>ǁ<I>c</I>, 13 T and 4.2 K), 14 times higher than that of pure Co-Ba122 thin film. Transmission electron microscopy observation revealed that BZO forms nanorods of ∼4 nm in average diameter with mean separation of 10–11 nm which corresponds to a matching field of about 17–20 T. Incorporating BZO in Co-Ba122 thin films led to a strong vortex pinning effect and a significant enhancement of <I>J</I> <SUB>c</SUB> because a high density of BZO nanorods could form in the superconducting matrix without significant degradation of <I>T</I> <SUB>c</SUB>, and the diameter of BZO nanorods is approximately twice the coherence length of Co-Ba122 (<I>ξ</I> <SUB>ab</SUB>(0) ∼ 2.5 nm) which is the optimal size as pinning centers.</P>