Correlation Between Enhanced ${\rm T}_{\rm c}$, the Unit Cell Volume and AC Magnetic Shielding in Argon Preheated $({\rm Y}_{1-{\rm x}}{\rm Eu}_{\rm x})({\rm SrBa}){\rm Cu}_{3}{\rm O}_{6+{\rm z}}$

Abstract

We report here on the preparation, X-ray diffraction with Rietveld refinement, resistivity and AC magnetic susceptibility measurements of (Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Eu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> )(SrBa)Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6.94</sub> . Each sample was subject to two types of heat treatment: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. For each x, the [AO] treatment increases the orthorhombicity ε (for 0 ≤ x ≤ 1), T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (for x ≥ 0.45) and by 6 K to 87 K for x = 1 [AO], and the distance d[Cu(1)-Sr/Ba] (decrease T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) for x <; 0.4 and decrease it (increase T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) for x >; 0.4. In the normal state, the [AO] treatment reduced the linear resistivity parameters indicating a diminution of the interaction of carrier charges with phonons. There was a remarkable improvement in the shielding effect S (amplitude of χ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">'</sup> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> )) in the case of the samples [AO] at all T <; T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and for any applied field for x >; 0.5. For each x and heat treatment, S(x) decreases when H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> and the temperature increase. Remarkable correlations were observed. A combination of several factors such as decrease in d[Cu(1)-(Sr/Ba)] ; increase in cationic and chain oxygen ordering; p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Sh</sub> and in-phase purity for the [AO] samples may account for the observed data.