Structural and superconducting property variations with nominal Mg non-stoichiometry in MgxB2 and its enhancement of upper critical field

Abstract

By applying a combination of characterisation tools, changes in structural and superconducting properties with nominal Mg non-stoichiometry in Mg xB2 are found. The non-stoichiometry produces enhanced in-field critical current densities (Jc's) and upper critical field / irreversibility field (Hc2/Hirr(T)) values. Upper critical fields of ∼ 21 T (4.2 K) were obtained in nominal Mg-deficient samples compared to ∼ 17 T (4.2 K) for near-stoichiometric samples. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.