Novel sample-thickness-dependent flux pinning behaviors of KFe <sub>2</sub> As <sub>2</sub> intercalations in CaKFe <sub>4</sub> As <sub>4</sub> single crystals
Chunlei Wang, He Tian, Qianqian Han, Chunfeng Fan, Qingbin Tang, Dong Chen, Qiankun Lei, Shujie Sun, Yingbin Li, Benhai Yu
Abstract
Abstract We report the strong dependence of critical current density ( J c ) on the sample thickness ( d ) along the crystalline c -axis in CaKFe 4 As 4 single crystals. The J c can be respectively enlarged more than 3 and 50 times in H parallel to c -axis ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>J</mml:mi> <mml:mrow> <mml:mtext>c</mml:mtext> </mml:mrow> <mml:mi>c</mml:mi> </mml:msubsup> </mml:math> ) and ab -plane ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>J</mml:mi> <mml:mrow> <mml:mtext>c</mml:mtext> </mml:mrow> <mml:mrow> <mml:mi>a</mml:mi> <mml:mi>b</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> ) at temperature of 5 K and high magnetic fields of 8 T when the d is reduced from 88 to 2.0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> . It is surprising to find that, accompanied by the enhanced J c , the fishtail effect fades away with the decreasing d . We believe that both the origins of enhanced J c and the fishtail effect in CaKFe 4 As 4 may have close relationship with the interlayer coupling between CaKFe 4 As 4 and the intercalations of KFe 2 As 2 . Our results not only demonstrate an encouraging prospect for application of CaKFe 4 As 4 , but also illuminate new light on the origin of fishtail effect in iron-based superconductors.