Shigeki Fujiyama

Two-dimensional Heisenberg behavior of J(eff)=1/2 isospins in the paramagnetic state of the spin-orbital Mott insulator Sr2IrO4.

The dynamical correlations of J(eff)=1/2 isospins in the paramagnetic state of spin-orbital Mott insulator Sr2IrO4 were revealed by resonant magnetic x-ray diffuse scattering. We found a two-dimensional antiferromagnetic fluctuation with a large in-plane correlation length exceeding 100 lattice spacings at even 20 K above the magnetic ordering temperature. In marked contrast to the naive expectation of the strong magnetic anisotropy associated with an enhanced spin-orbit coupling, we discovered an isotropic isospin correlation that is well described by the two-dimensional S=1/2 quantum Heisenberg model. The estimated antiferromagnetic coupling constant as large as J∼0.1  eV that is comparable to the small Mott gap (<0.5  eV) points out the weak and marginal Mott character of this spin-orbital entangled system.

Weak antiferromagnetism ofJeff=12band in bilayer iridate Sr3Ir2O7

The antiferromagnetic structure of Sr3Ir2O7, the bilayer analogue of a spin-orbital Mott insulator Sr2IrO4, was revealed by resonant magnetic x-ray diffraction. Contrasting intensities of the magnetic diffraction at the Ir LIII and LII edges show a Jeff=1/2 character of the magnetic moment as is argued in Sr2IrO4. The magnitude of moment, however, was found to be smaller than that of Sr2IrO4 by a factor of 5-6, implying that Sr3Ir2O7 is no longer a Mott insulator but a weak antiferromagnet. An evident change of the temperature dependence of the resistivity at TN, 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 inplane canted antiferromagnetism in Sr2IrO4, originating from the strong bilayer antiferromagnetic coupling.

Charge freezing in the zigzag chain PrBa2Cu4O8 cuprate.

We report nuclear quadrupole resonance (NQR) studies on the chain Cu sites of PrBa

Spin and orbital contributions to magnetically ordered moments in 5d layered perovskite Sr2IrO4.

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Redistribution of Electronic Charges in Spin-Peierls State in (TMTTF)2AsF6 Observed by 13C NMR

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Suppression of electronic susceptibility in metal–Mott-insulator alternating material ( Me − 3 , 5 − DIP ) [ Ni ( dmit ) 2 ] 2 observed using C 13 NMR

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Nuclear Spin Relaxation in Hole Doped Two-Leg Ladders

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Compensation of Effective Field in the Field-Induced Superconductor kappa-(BETS)~2FeBr~4 Observed by ^7^7Se NMR

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Magnetic and 1H-NMR Spectroscopic Studies of [Ph(NH3)](18-crown-6) [Ni(dmit)2] Having Molecular Spin Ladder Structure

, a quasi-one-dimensional conductor with a nearly quarter-filled band. The nuclear spin-lattice relaxation rate

Nuclear spin-spin coupling in La 2 − x Sr x CuO 4 studied by stimulated echo decay

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