2012/03/09 by S. Fujiyama, Shigeki Fujiyama, H. Ohsumi +10 · 5 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Anisotropy #Antiferromagnetism #Condensed matter physics #Magnetic and transport properties of perovskites and related materials #Mott insulator #Paramagnetism #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Spin (aerodynamics) #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.108.247212
arxiv created 2012/03/09 · openalex publication_date 2012/06/15 · arxiv updated 2015/06/04 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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.