Superconductivity in Ferromagnetic RuSr2GdCu2O8

W. E. PICKETT; R. WEHT; A. B. SHICK1

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Año: 1999 vol. 83 p. 3713 - 3716

0031-9007

Relying on the inhomogeneous (layered) crystal, electronic, and magnetic structure, we show how superconductivity can coexist with the ferromagnetic phase of RuSr2GdCu2O8 as observed by Tallon and co-workers. Since the Cu d_x2-y2 orbitals couple only to apical O_px/py orbitals (and only weakly), which also couple only weakly to the magnetic Ru_t2g orbitals, there is sufficiently weak exchange splitting, especially of the symmetric CuO2 bilayer Fermi surface, to allow singlet pairing. The exchange splitting is calculated to be large enough that the superconducting order parameter may be of the Fulde-Ferrell-Larkin-Ovchinnikov type.