Microstructural and Pinning Properties of ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta}$ Thin Films Doped With Magnetic Nanoparticles

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we report a strong enhancement in the in-field transport properties of the <formula formulatype="inline"><tex Notation="TeX">${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta}$</tex></formula> (YBCO) thin films doped with magnetic <formula formulatype="inline"><tex Notation="TeX">${\rm Fe}_{2}{\rm O}_{3}$</tex></formula> nanoparticles. We incorporated magnetic <formula formulatype="inline"><tex Notation="TeX">${\rm Fe}_{2}{\rm O}_{3}$</tex></formula> nanoparticles with two different architectures by laser ablation of the YBCO and dopant targets. YBCO film thickness was controlled at around 1 <formula formulatype="inline"> <tex Notation="TeX">$\mu{\rm m}$</tex></formula> for all the samples. We conducted a detailed microstructural characterization on all the doped samples by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM) and compared with the pure YBCO films. A systematic study on the superconducting properties has been conducted on all the thin film samples. The critical current densities at both self-field and in-field (<formula formulatype="inline"> <tex Notation="TeX">$J_{c}^{sf}$</tex></formula> and <formula formulatype="inline"> <tex Notation="TeX">$J_{c}^{in-field}\ ({\rm H}//c)$</tex></formula>) and the critical transition temperature <formula formulatype="inline"><tex Notation="TeX">$(T_{c})$</tex> </formula> of the doped and un-doped YBCO sample were measured by a Superconducting Quantum Interference Device (SQUID). The <formula formulatype="inline"><tex Notation="TeX">$T_{c}$</tex></formula> of the doped YBCO films varies from 84 K–90 K and the <formula formulatype="inline"><tex Notation="TeX">$J_{c}$</tex> </formula> is in the range of 1.2–3.9 <formula formulatype="inline"> <tex Notation="TeX">${\rm MA/cm}^{2}$</tex></formula> (at 65 K) depending on the doping approach. The pinning properties of these doped YBCO films were explored at different temperatures (5 K, 40 K, and 65 K) and correlated with their microstructural characteristics. </para>