• Raghav, D. S.
• Chauhan, Shital
• Kumari, Suman
• Anas, Mohd
• Siwach, P. K.

Abstract

<jats:title>Abstract</jats:title><jats:p>We report a detailed study on the magnetotransport behavior of YBa<jats:sub>2</jats:sub>Cu<jats:sub>3</jats:sub>O<jats:sub>7-<jats:italic>δ</jats:italic></jats:sub>-Sm<jats:sub>0.55</jats:sub>Sr<jats:sub>0.45</jats:sub>MnO<jats:sub>3</jats:sub> (YBCO-SSMO) superconducting-ferromagnetic composite thin films (thickness ∼80 nm) of nominal compositions (YBCO)<jats:sub>1-x</jats:sub>(SSMO)<jats:sub>x</jats:sub> (x = 0, 0.08, and 0.14). Films are grown by pulsed laser deposition of the pure and composite targets on (001)-SrTiO<jats:sub>3</jats:sub> substrates, and all are single crystalline with the <jats:italic>c</jats:italic>-axis normal to the plane of the substrate. The T<jats:sub>c</jats:sub>(R = 0) of the pure YBCO film is ≈87 K and decreases to ≈75 K and ≈44 K with the incorporation and increase of the ferromagnetic fraction in the superconducting matrix. Successive decrease in the slope of the normal state R-T curves maps the incorporation of the high resistance channels of the SSMO. In an external magnetic field (H), the rate of decrement in the T<jats:sub>c</jats:sub>(R = 0) is found to be dT<jats:sub>c</jats:sub>(R = 0)/dH ∼1.8 K T<jats:sup>−1</jats:sup>, ∼4.7 K T<jats:sup>−1</jats:sup>, and ∼2.8 K T<jats:sup>−1</jats:sup>, respectively for x = 0, 0.08, and 0.14. The upper critical field and the irreversibility field are appreciably depressed in the composite samples and suggest a broadening of the mixed-phase vortex regime. The application of the thermally activated flux flow (TAFF) model shows that the activation energy decreases sharply from U<jats:sub>0</jats:sub> = 4314 (910) meV, 498 (130) meV, and 253 (66) meV for YS00, YS08, and YS14, respectively, at H = 0 T (6 T). The analysis of the field-dependent activation energy in terms of <jats:inline-formula><jats:tex-math> <?CDATA ${{{U}}}_{0} {{{H}}}^{- }$?> </jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msub><mml:mrow><mml:mi mathvariant="normal">U</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub><mml:mo>∼</mml:mo><mml:msup><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mi>α</mml:mi></mml:mrow></mml:msup></mml:math><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="psac74f1ieqn1.gif" xlink:type="simple" /></jats:inline-formula> and <jats:inline-formula><jats:tex-math> <?CDATA ${{{U}}}_{0} -{{U}}\,{log}\,{{H}}$?> </jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msub><mml:mrow><mml:mi mathvariant="normal">U</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub><mml:mo>≈</mml:mo><mml:mo>−</mml:mo><mml:mi mathvariant="normal">U</mml:mi><mml:mspace width=".25em" /><mml:mi>log</mml:mi><mml:mspace width=".25em" /><mml:mi mathvariant="normal">H</mml:mi></mml:math><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="psac74f1ieqn2.gif" xlink:type="simple" /></jats:inline-formula> dependence suggests decoupling of the 2D vortices due to the ferromagnetic phase. The hysteresis in the current-voltage characteristics is seen to decrease with an increase in the SSMO content.</jats:p>

Topics

• impedance spectroscopy
• phase
• thin film
• composite
• activation
• pulsed laser deposition