Muralidhar M, Sakai N, Chikumoto N, Jirsa M, Machi T, Nishiyama M, Wu Y, Murakami M
Superconductivity Research Laboratory (SRL), International Superconductivity Technology Center, Division III, 1-16-25, Shibaura, Minato-ku, Tokyo, 105-0023, Japan.
Phys Rev Lett. 2002 Dec 2;89(23):237001. doi: 10.1103/PhysRevLett.89.237001. Epub 2002 Nov 13.
We report on a new type of correlated nanometer-scale pinning structure observed in a melt-processed (Nd0.33Eu0.38Gd0.28)Ba(2)Cu(3)O(y) (NEG-123). It consists of NEG/Ba-rich clusters in the stoichiometric NEG-123 matrix forming a lamellar array with a period of a few nanometers. These lamellas appear within regular twins, thus representing their fine substructure-sometimes straight, sometimes wavy. This new material structure correlates well with the significant enhancement of pinning at high fields, represented by irreversibility field above 14 T at 77 K (B parallel c). We believe that the new pinning medium enables one to significantly broaden the limits for high-field applications.
