The Effects of Chemical Doping on the Diamagnetic Thermodynamic Fluctuations of YBa2Cu2.97X0.03O7-δ (X = Au, Ni, Zn, and Mg) Single Crystals

Abstract

In this article, we investigated the effects of chemical doping on the diamagnetic thermodynamic fluctuations (DTFs) of YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.97</sub> X <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.03</sub> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{7-\delta}$ </tex-math></inline-formula> (X = Au, Ni, Zn, and Mg) single crystals. In-plane dc zero field cooled [ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M_{\mathrm {ZFC}}(T)$ </tex-math></inline-formula> ] and field cooled cooling [ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M_{\mathrm {FCC}}(T)$ </tex-math></inline-formula> ] magnetizations were measured with a superconducting quantum interference device (SQUID) magnetometer while magnetic fields ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> ) ranging from 0.01 up to 50 kOe were applied. The DTF contribution on the reversible <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M_{\mathrm {ZFC}}(T)$ </tex-math></inline-formula> magnetization was accounted by applying 3D-XY and 3-D lowest Landau level (3D-LLL) scaling functions. The results show that the DTF contribution on the reversible <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M_{\mathrm {ZFC}}(T)$ </tex-math></inline-formula> data of our samples is well described by the 3D-XY scaling function when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H \le 1$ </tex-math></inline-formula> kOe (low-magnetic-field regime) is applied and by the 3D-LLL scaling function when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H &gt; 10$ </tex-math></inline-formula> kOe (high-magnetic-field regime) is applied. The reversible <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M_{\mathrm {ZFC}}(T)$ </tex-math></inline-formula> data of the doped samples display in the low-magnetic-field regime a rounded of the DTF regime around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm {C}}$ </tex-math></inline-formula> and a temperature enlargement of the DTF regime range in the high-magnetic-field regime. We believe that these effects are connected to intensification of YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{7-\delta}$ </tex-math></inline-formula> inhomogeneous superconducting state caused by individual partial substitution of ≈1% of Cu for chemical dopants listed above.