Flux pinning by inclusions in superconductors: A combined effect of point, interface, and pinning at elevated temperatures

We have systematically studied the role of (Formula presented) (Nd422) nonsuperconducting inclusions for flux pinning in oxygen-controlled-melt-growth processed Nd-Ba-Cu-O bulk superconductors. Nd422 inclusions act as interface pinning which is the most dominant in low-field and high-temperature region. In addition, they are also effective in enhancing the critical current density (Formula presented) even in a high-field region and thus the irreversibility field (Formula presented) Three pinning regimes have been identified at elevated temperatures (Formula presented) K): a combination of point and interface pinning in low fields; a combination of interface and (Formula presented) pinning in intermediate fields; and interface pinning with a slight influence from (Formula presented) pinning in high fields. Nd422 addition shifted the boundary of the pinning regime to higher fields. We have found overall (Formula presented) is almost a simple summation of two contributions: interface pinning and (Formula presented) pinning.