Effect of Magnetic NiO Nanoparticles on Pinning Properties of YBa₂Cu₃O_7-x Superconductor

In the present work, we report the effects of incorporating magnetic Nickel oxide (NiO) nanoparticles in YBa₂Cu₃O_7-x (YBCO), on the superconducting properties of the YBCO nanocomposite. The NiO was prepared by auto-combustion method and exhibited ferromagnetic nature at room temperature. The polycrystalline YBCO and its nanocomposites with NiO nanoparticles were synthesized using the solid-state reaction method. The addition of magnetic NiO nanoparticles in YBCO resulted in improved critical current density and flux pinning force in the measured range of temperature and magnetic fields. The observed high pinning at a lower field is attributed to the magnetic interaction of vortices with the NiO nanoparticles. At 60 K, the enhancement in critical current density of YBCO nanocomposite is ~ 1.7 times for low applied field, and ~ 1.2 times for high applied field, compared to the YBCO superconductor. The presence of NiO in the YBCO matrix also created more defects in YBCO, which enhanced the pinning properties and remained effective even at higher magnetic fields.