A Co(IV)-rich 2D ferromagnet with magnetoresistance properties: Sr3FeCoO7−δ

The new cobalt IV rich oxide Sr3FeCoO6.94, n=2 member of the Ruddlesden–Popper series, is reported. Electron and X-ray diffraction confirm the tetragonal symmetry (space group: I4/mmm, with cell parameters: a=3.8403(3) Å and c=20.025(2) Å). The magnetic susceptibility and isothermal magnetisation curves demonstrate the existence of ferromagnetism. The magnetic behavior, characterized by a glassy state, is closely correlated to a change in the transport properties. Accordingly, the Sr3FeCoO6.94 compound exhibits a negative magnetoresistance effect of −24% at 10 K under 7 T.