Locking of iridium magnetic moments to the correlated rotation of oxygen octahedra in Sr₂IrO₄revealed by x-ray resonant scattering

Abstract

Sr2IrO4 is a prototype of the class of Mott insulators in the strong spin-orbit interaction (SOI) limit described by a Jeff = 1/2 ground state. In Sr2IrO4, the strong SOI is predicted to manifest itself in the locking of the canting of the magnetic moments to the correlated rotation by 11.8(1)° of the oxygen octahedra that characterizes its distorted layered perovskite structure. Using x-ray resonant scattering at the Ir L3 edge we have measured accurately the intensities of Bragg peaks arising from different components of the magnetic structure. From a careful comparison of integrated intensities of peaks due to basal-plane antiferromagnetism, with those due to b-axis ferromagnetism, we deduce a canting of the magnetic moments of 12.2(8)°. We thus confirm that in Sr2IrO4 the magnetic moments rigidly follow the rotation of the oxygen octahedra, indicating that, even in the presence of significant non-cubic structural distortions, it is a close realization of the Jeff = 1/2 state.

Anisotropic Magnetoresistance in AntiferromagneticSr2IrO4

“…3) occurs over the same field range, suggesting its possible relationship with the magnetic transformations in IrO 2 planes. As was pointed out in previous studies of the magnetic order in Sr 2 IrO 4 [24][25][26], the magnetic moments tend to follow octahedral-site rotation because of a strong spin-orbit coupling and, therefore, a strong single ion anisotropy in Sr 2 IrO 4 . Since the electronic properties of Sr 2 IrO 4 are also known to be sensitive to lattice distortions [15,20], it is possible that the observed magnetic field dependence of AMR symmetry in our study can be associated with lattice distortions that originate from the magnetoelastic effect and spin-orbit coupling.…”

Influence of electron doping on the ground state of(Sr1−xLax)2IrO4

“…≈ 60 meV 17 drives short-range, quasi-two-dimensional correlations to persist to much higher temperatures 6 . Once ordered, AF moments of µ AF ≈ 0.35µ B 18 remain locked to the in-plane octahedral tilts 19 , generating a weak ferromagnetic response under an applied in-plane field and an eventual metamagnetic transition beyond a critical µ 0 H C ≈ 0.2 T 9,11 . The conventional picture of this canted state is that, due to the near negligible easy-axis anisotropy within the abplane 20 , the net moment due to canting can be rotated and rapidly polarized by a very weak in-plane field.…”

The contribution of Diamond Light Source to the study of strongly correlated electron systems and complex magnetic structures

“…Much of the experimental effort has focused on the attempt to confirm the existence of the J eff = [78,79] determined the magnetic structure of Sr 3 Ir 2 O 7 by REXS and also imaged the magnetic domains, which were found to be of the order of 100 µm. The work of the McMorrow group on the single-layer materials focused on exploring the robustness of the conclusion that these systems are representative of the J eff = 1 2 state, traditionally inferred from the L 2 /L 3 branching ratio for different spin directions and in the presence of significant lattice distortions [80,81]. One important result they obtained is that the possibility of observing the J eff = 1 2 state by REXS is limited to specific states, i.e.…”

“…The group of Marrows (Leeds) have also studied the effects of Gd doping in Ni 80 Fe 20 nanowires on the depinning current densities using the Nanoscience beamline (I06). Gd doping was shown to give rise to additional spin-flip scattering leading to lower current densities required to depin and move domain walls from pinning centres [107,108].…”