Structural chemistry and electronic properties of Sr2FelrO6

A polycrystalline sample of Sr2FeIrO6 has been synthesized and shown by a combination of X-ray diffraction, neutron diffraction, magnetometry, and Mossbauer spectroscopy to be a triclinic (space group I (1) over bar; a = 5.54996(3) Angstrom, b = 5.57847(3) Angstrom, c = 7.84165(3) Angstrom, a = 89.990(1)degrees, beta = 90.059(1)degrees, gamma = 90.079(1)degrees) 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 Mossbauer data suggest that similar to 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) mu(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, (C) 1999 Academic Press.