Coexistence of superconductivity and ferromagnetism in P-doped EuFe2As 2

The magnetic structure of the Eu2+ moments in the superconducting EuFe2(As1-xPx)2 sample with x=0.15 has been determined using element-specific x-ray resonant magnetic scattering. Combining magnetic, thermodynamic, and scattering measurements, we conclude that the long-range ferromagnetic order of the Eu2+ moments aligned primarily along the c axis coexists with the bulk superconductivity at zero field. At an applied magnetic field ≥0.6 T, superconductivity still coexists with the ferromagnetic Eu2+ moments, which are polarized along the field direction. We propose a spontaneous vortex state for the coexistence of superconductivity and ferromagnetism in EuFe2(As0.85P0.15)2.