Infield Superconducting Transport Properties of Magnetic Nanostructures-CuTl-1223 Composites

Abstract

(M)x-CuTl-1223; M = Ni, Co, CoFe2O4, Cr, Al2O3, nanoparticles-superconductor composites were synthesized by solid-state reaction (ceramic method) and their infield (magnetic) superconducting properties were investigated. Structural, morphological and compositional analysis of these composites were carried by using X-rays diffraction (XRD) analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively. The infield transport measurements were carried out by resistance versus temperature (RT) measurements with small current (˷10 μA) by using four-probe technique with the help of physical properties measurement system (PPMS). Broadening in superconducting transition region was observed with increasing the external applied magnetic field (H) in all the samples, which was attributed to thermally activated flux flow (TAFF). Flux pinning strength was calculated by using TAFF model. The field dependent flux flow activation energy {Uo(H)} of CuTl-1223 superconducting matrix was increased with addition of ferri-magnetic (CoFe2O4) and antiferromagnetic (Cr) nanoparticles up to certain optimum level of concentration. The transition width (ΔT) of CuTl-1223 phase was decreased after addition of these nanoparticles. The enhancement in Uo(H) and reduction in ΔT show improvement in flux pinning ability of CuTl-1223 matrix with addition of CoFe2O4 and Cr nanoparticles. The flux pinning strength of CuTl-1223 phase was decreased with addition of ferromagnetic (Ni and Co) and non-magnetic (Al2O3) nanoparticles. It was observed that Uo(H) decreases and ΔT increases with the addition of these nanoparticles. The suppression in Uo(H) with increasing magnetic field obeys the power law (Uo = β H-). The value of ‘’ corresponds to the suppression rate of Uo(H) with H. The decrease in ‘’ with the addition of Cr, Co, and Al2O3 nanoparticles showed that the decreasing rate of activation energy with increasing H is lowered with addition of these nanoparticles. Thus although the addition of Co and Al2O3 in CuTl-1223 matrix decreases its flux pinning but their addition has lowered the suppression rate of Uo(H) with H, which shows that the inclusion of these nanoparticles can make CuTl-1223 superconductor suitable for high field applications. In case of addition of CoFe2O4 and Ni nanoparticles in CuTl-1223 superconductor, value of ‘’ increases which indicates that lowering rate of activation energy increases with the rise in H. The transition width (ΔT) was increased with the rise in H, which shows TAFF takes place in the samples with small current. It was observed that broadening in ΔT with ‘H’ obeys a power law (ΔT = ΔTo + CHn) where ΔTo is the transition width in absence of applied field.