Insulating nanoparticle induced pinning in YBCO superconductor. Crossover from collective to strong pinning regimes

Both the transport critical current density at the zero magnetic field and magnetic critical current density in a composite system consisting of bulk YBCO superconductor and insulating BaTiO${}_3$ (BTO) have been studied using current-voltage (IV) and magnetization (M) as a function of magnetic field (H), respectively. Vortex pinning by insulating nanoparticles of BTO from the inter-granular network is investigated up to the magnetic field of 7.0 T. By analyzing magnetic critical current density the possibility of crossover from collective pinning (CP) to strong pinning (SP) and how it is affected by BTO have been explored based on the framework of Larkin-Ovchinnikov (LO) theory. Possible scenario of the strong pinning (SP) induced by insulating nanoparticles has also been studied using an exponent.