Critical Properties of Bulk-Doped BaFe2As2 Pnictides for Magnet Design.

comprehensive study of upper critical (Hc2) and irreversibilitymagnetic fields (Hirr ) in (Ba0.6 K0.4 )Fe2As2 (critical temperature Tc = 38.3 K), Ba(Fe0.95 Ni0.05 )2As2 (Tc = 19.2 K), Ba(Fe0.94 Ni0.06 )2As2 (Tc =18.5 K),Ba(Fe0.92Co0.08 )2 As2 (Tc = 23.2 K), and Ba(Fe0.91Co0.09)2As2 (Tc = 25.3 K) polycrystalline bulk pnictide superconductors with different average grain sizes was made in pulsed fields at the Los Alamos National Laboratory. Themagnetic field-temperature (Hc2 -T) phase diagramswithHc2 as high as 65 T at 28Kfor theK-doped samples and critical current density (Jc) measurements as high as 105 A/cm2 for the smallest, submicrometer grain size samples were obtained. The high Hc2, Hirr, and Jc data show the suitability of these materials for magnet design as their mechanical strength and random grain alignment show promise in the manufacturing of next-generation magnets. [ABSTRACT FROM AUTHOR]