J Supercond Nov Magn DOI 10.1007/s10948-017-4293-0 ORIGINAL PAPER Ni Nanoparticle-Added Ni x /(Cu 0.5 Tl 0.5 )Ba 2 Ca 2 Cu 3 O 10-δ Superconductor Composites and Their Enhanced Flux Pinning Characteristics Nawazish A. Khan 1 · Abida Saleem 1,2 · S. Qamar Abbas 1 · M. Irfan 3 Received: 3 May 2017 / Accepted: 9 August 2017 © Springer Science+Business Media, LLC 2017 Abstract Ni nanoparticle-added Ni x /(Cu 0.5 Tl 0.5 )Ba 2 Ca 2 Cu 3 O 10-δ superconductor composites are synthesized at nor- mal pressure by two-step solid-state reaction method. The idea for adding ferromagnetic nanoparticles was to create artificial pinning centers at grain boundaries. The samples have shown orthorhombic crystal structure in which the cell parameters increase with an increase in the added con- centration of Ni nanoparticles. This shows that due to the higher reactivity, Ni nanoparticles partially diffuse into the unit cell of (Cu 0.5 Tl 0.5 )Ba 2 Ca 2 Cu 3 O 10-δ superconductors. This also indicates as an evidence of the occupancy of these nanoparticles at grain boundaries. A metallic varia- tion of resistivity from room temperature down to the onset of superconductivity is a typical feature of these samples with T c (R = 0) varying between 92 and 94 K. The mag- nitude of diamagnetism is significantly enhanced in 7 and 10% nanoparticle-added samples. The enhanced magnetiza- tion of ferromagnetic nanoparticles at reduced temperature plays a vital role in reducing the diamagnetism of nanosu- perconductor composites. The softening of apical oxygen modes of type Cu(1)–O A –Cu(2) has confirmed the dif-  Nawazish A. Khan nakhan@qau.edu.pk 1 Materials Science Laboratory, Department of Physics, Quaid-i-Azam University, Islamabad 45320, Pakistan 2 National Center for Physics, Shadhara Valley Road Quaid-i-Azam University Campus, 44000, Islamabad, Pakistan 3 Department of Physics, University of Mir-Pur, Azad Kashmir, Pakistan fusion of Ni nanoparticles into the unit cell of the final compound. The excess conductivity analyses of conduc- tivity data have shown that the values of B c (0), B c1 , and J c are enhanced with the addition of Ni nanoparticles in the final compound. Variation of superconducting proper- ties was attributed to pair breaking due to spin scattering across these ferromagnetic Ni nanoparticles. This shows that added Ni nanoparticles act as efficient pinning centers, which is also confirmed by the suppression of the London penetration depth. Keywords Ni x /(Cu 0.5 Tl 0.5 )Ba 2 Ca 2 Cu 3 O 10-δ composite superconductors · Excess conductivity analysis · Enhancement of B c (0), B c1 , and J c · Enhancement of flux pinning · Suppression of London penetration depth 1 Introduction The impact of superconducting materials from their applica- tion point of view can be estimated from the values of super- conducting critical parameters such as critical temperature T c , critical current density J c , and critical magnetic field H c [1, 2]. The values of these superconductivity parameters are higher in (Cu 0.5 Tl 0.5 )Ba 2 Ca 2 Cu 3 O 10-δ superconductors and initially, this material was prepared under high pressure. For the mass production of this material for device fabri- cation and wire applications, attempts have been made to synthesize it at normal pressure [3–6]. However, one of the major root causes which can limit the performance of these materials is inter-grain voids which can produce inhomo- geneous macro-defects that limit the transport J c and other superconductivity parameters. A convenient way to tackle this problem is the inclusion of metallic nanoparticles at