Effect of Mo-substitution on superconductivity, flux pinning and critical currents of La1.5Nd0.5Ca1Ba2Cu5Oz

Abstract

Mo-substituted triple perovskite superconducting samples with stoichiometric composition La 1.5 Nd 0.5 Ca 1 Ba 2 (Cu 1-x Mo x ) 5 O z with x = 0.00, 0.01, 0.03, 0.05 and 0.10, have been investigated using X-ray diffraction, electrical resistivity, magnetic susceptibility and Magnetization measurements. Oxygen content has also been determined by the iodometric technique. The observed reduction in superconducting transition temperature, T c , in this system with increasing Mo content can be attributed to the decrease in hole concentration. Magnetization measurements as a function of temperature and field (H), exhibit an M-H hysteresis loop which indicates moderate flux pinning, which is thought due to pinning centers created by Mo substitution at Cu sites. The critical current density, J c , deduced from the M-H data satisfies the flux creep model.

Thermal expansion measurements using x-ray powder diffraction of Tl-1223 substituted by molybdenum

“…The zero-resistivity temperature T 0 decreased from 119.5 to 91.5 K for 20% Mo substitution of Cu at an average rate of about 1.4 K/at.%. This value is less than that reported by Rayaprol et al [8] in La 1.5 Nd 0.5 CaBa 2 Cu 5 O z , who found T 0 decreased at an average rate of 4.0 K/at.%.…”

“…Both T c and θ D are suppressed as the Mo content increases. The suppression in T c as Mo content increases is attributed to the uniaxial pressure induced by the changing of the Jahn-Teller effect and the hole-filling mechanism [8], whereas the depression in Debye temperature is probably due to the partial replacement of light Cu 2+ ions by the heavier Mo 4+ ions which may reduce the frequency of lattice vibration (phonon). Also, the value of θ D for the unsubstituted sample, x = 0.0, is consistent with that determined from specific heat measurements [13,16].…”

“…They showed that Mo substitution produced a point defect that enhanced the source of flux pinning and reduced the anisotropy of this system. Rayaprol et al [8] prepared La 1.5 Nd 0.5 CaBa 2 (Cu 1−x Mo x ) 5 O z and observed a reduction in T c with increasing Mo content. The reduction in T c was attributed to the decreased hole concentration in CuO 2 planes.…”

Neutron diffraction studies on La2−x Dy x Ca2xBa2Cu4+2x Oz superconductors

“…Superconductivity in La 2 Ba 2 Cu 4 O z (La-224) can be induced by the simultaneous addition of CaO and CuO in the stoichiometric composition La 2-x R x Ca 2x Ba 2 Cu 4+2x O z where R = rare earth, and x = 0.1 -0.5 (i.e., La-2125 phase for x = 0.5) [1]. Several studies have been carried out in understanding the origin of superconductivity in these types of oxides [2][3][4]. The R ion in La-2125 type compounds provides structural stability without any effect on superconductivity similar to the role of R ion at Y-site in Y-123 superconductors.…”