Magnetic states in quasi-2-D iridium oxides with large spin-orbit coupling

The magnetic states in the novel K 2 NiF 4 -type quasi-2-D spin-orbit-induced Mott insulator Ba 2 IrO 4 was studied using magnetic susceptibility, muon spin rotation (µSR), and high-pressure resistivity measurements. In Ba 2 IrO 4 , a Néel ordered state was found to be stabilized at temperatures below T N (Néel temperature) ∼ 240 K. The critical exponent β ∼ 0.18 suggests a quasi-2-D Heisenberg antiferromagnetic state on the IrO 2 planar square lattice. The magnetic moment is significantly reduced to ∼0.34 µ B /Ir-atom, probably due to a low-dimensional quantum spin fluctuation with a large magnetic intra-plane correlation | J |. A non-Fermi liquid-like behavior with carrier scattering due to the spin fluctuation was observed in the metallic state under high pressures of more than 13.8 GPa.