Chemical tuning of ferromagnetism and superconductivity in RuSr2GdCu2O8Electronic supplementary information (ESI) available: Rietveld refinement patterns [Fig. 1(a)–(c)] and characterisation data (Table 1). See http: //www.rsc.org/suppdata/cc/b0/b002669g

Abstract

When substituted for Ru in the ferromagnetic superconductor RuSr₂GdCu₂O₈, both Sn⁴⁺ and Nb⁵⁺ suppress the ferromagnetism in the RuO₂ layers, but they respectively enhance and diminish superconductivity in the CuO₂ planes through hole transfer to and from the CuO₂ layers, showing that these materials are underdoped with an estimated maximum T_c of 65 ± 10 K.