Pinning analyses of a BaHfO <sub>3</sub> -containing GdBa <sub>2</sub> Cu <sub>3</sub> O <sub>7‐δ</sub> thin film grown by chemical solution deposition
K. Iida, Pablo Cayado, Hannes Rijckaert, Manuela Erbe, Jens Hänisch, Tatsunori Okada, Isabel Van Driessche, Satoshi Awaji, B. Holzäpfel
Abstract
Abstract The electric transport properties of a GdBa 2 Cu 3 O <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi/> <mml:mrow> <mml:mn>7</mml:mn> <mml:mo>−</mml:mo> <mml:mi>δ</mml:mi> </mml:mrow> </mml:msub> </mml:math> thin film containing 12 mol% nano-sized BaHfO 3 (BHO) particles grown by chemical solution deposition were investigated in a wide range of temperatures (4.2 ≤ T ≤ 77 K) and magnetic fields up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext/> </mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> </mml:msub> <mml:mi>H</mml:mi> </mml:math> = 19 T. The exponent n of the electric field–current density characteristics ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>E</mml:mi> <mml:mo>∝</mml:mo> </mml:math> J n ) depends on critical current density <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>J</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext/> </mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> </mml:math> as ( n –1) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∝</mml:mo> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mi>J</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext/> </mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> ( α ∼ 0.45) irrespective of measurement temperature for H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∥</mml:mo> </mml:math> c . On the other hand, this relation does not hold for H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∥</mml:mo> </mml:math> ab . The angular dependence of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>J</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext/> </mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> </mml:math> is almost similar to that of n except for the angle close to the ab -plane. A dip of n around this angle regime was observed below 77 K, whereas <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>J</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext/> </mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> </mml:math> exhibited a maximum. At T ≤ 50 K a tiny peak in the dip was observed that increases with decreasing temperatures. These results suggest that the pinning mechanism changes with temperature for H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∥</mml:mo> </mml:math> ab .