The antiferromagnetic structure of Sr 3Ir 2O 7, the bilayer analog of a spin-orbital Mott insulator Sr 2IrO 4, was revealed by resonant magnetic x-ray diffraction. Contrasting intensities of the magnetic diffraction at the Ir L III and L II edges show a J eff=1/2 character of the magnetic moment as is argued in Sr 2IrO 4. The magnitude of moment, however, was found to be smaller than that of Sr 2IrO 4 by a factor of 5 to 6, implying that Sr 3Ir 2O 7 is no longer a Mott insulator but a weak antiferromagnet. An evident change of the temperature dependence of the resistivity at T N, from almost temperature-independent resistivity to insulating, strongly suggests that the emergent weak magnetism controls the charge gap. The magnetic structure was found to be an out-of-plane collinear antiferromagnetic ordering in contrast to the in-plane canted antiferromagnetism in Sr 2IrO 4, originating from the strong bilayer antiferromagnetic coupling.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2012 Nov 16|