Xu et al. observed enhanced Nernst effect and Iguchi et al. observed patched diamagnetism, both well above Tc in underdoped high-Tc superconductors (HTSCs). A new mechanism is proposed here, which seems to naturally explain, at least qualitatively, these observations, as well as the d-wave nature and continuity of pseudogap and pairing gap, the tunneling conductance above Tc, as well as T*(x), Tν(x), Tc(x), etc. This mechanism combines features of dynamic charged stripes, preformed pairs, and spin-bags: At appropriete doping levels, the doped holes (and perhaps also electrons) will promote the formation of anti-phase islands in short-range anti-ferromagnetic order. On the boundary of each such island reside two doped carriers; the unscreened Coulomb repulsion between them stabilizes the island's size. Superconductivity results when such "pre-formed pairs" Bose-condense.
Short-range ferromagnetic order due to Ir substitutions in single-crystalline Ba(Co1− x Ir x )2As2 (0 ⩽ x ⩽ 0.25)
