Competing Ferromagnetism and Superconductivity on FeAs Layers inEuFe2(As0.73P0.27)2

Abstract

We have measured the spin-polarized electron momentum density distributions of EuFe2(As0.73P0.27)2 by magnetic Compton scattering (MCS) measurements. For the first time, we show direct evidence of competing ferromagnetism and superconductivity (SC) on FeAs layers in this iron pnictide system. The MCS orbitalwise decomposition of the density distributions reveals that between 16 and 19 K, the spin-polarized Fe-3d character is enhanced (as the ferromagnetic character supersedes superconducting character), where the resistivity shows a maximum, reentrant SC-like peak, at 18 K. The spin polarization of the Fe-3d orbital, enhanced by ferromagnetic Eu ions, suppresses the SC around 18 K, while at other temperatures the system indeed exhibits SC where the Fe-3d spin polarization is suppressed or collapses.