As the pinning performance due to secondary phase particles is inversely proportional to the average particle size, a successful refinement of the secondary phase particles up to nanometer level resulted in a considerable increase of super-current density at 77 K. The samples exhibited not only the highest Jc ever reported for bulk melt-processed samples but also enabled for the first time levitation at liquid oxygen temperature (90.2 K). The new nanometer-scale pinning medium, with size in the range 20-50 nm, was composed of Zr-rich ball-milled Gd-211 particles. The super-current density reached 200 and 110 kA/cm2 at 0 and 3 Tesla, respectively, and 55 kA/cm2 at 90 K in the remnant state. We thus reached the internal ISTEC goal in electro-magnetic properties of materials intended for large-scale bulk applications. For details, see the paper by Muralidhar et al., Applied Physics Letters 83, 5005 (2003). These results were covered by Japanese patent No. KN02B317-2, Date of filling March 31, 2005.
