Structural Chemistry and Electronic Properties of Sr2FeIrO6

A polycrystalline sample of Sr2FeIrO6 has been synthesized and shown by a combination of X-ray diffraction, neutron diffraction, magnetometry, and M?ssbauer spectroscopy to be a triclinic (space group I ; a=5.54996(3) ?, b=5.57847(3) ?, c=7.84165(3) ?, =89.990(1)°, =90.059(1)°, =90.079(1)°) perovskite, with a partially ordered (0.928:0.072(4)) distribution of transition metal cations over the six-coordinate sites. The predominant oxidation states are Fe3+ and Ir5+, although the M?ssbauer data suggest that ~4% Fe4+ is present. The compound is a Type II antiferromagnet below 120 K, with an ordered magnetic moment on the Fe-dominated sites of 3.67(3) B per Fe3+ cation. The spins associated with the antisite defects are frustrated and do not take part in the long-range magnetic ordering, consequently giving rise to hysteresis in the magnetic susceptibility below 40 K. The possible location of the Fe4+ cations is discussed briefly.