Search NASA⌕ Search

SEARCH · Search NASA

Results for “Sr2IrO4”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sr2IrO4 by Materials Project

Sr2IrO4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sr2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.44–2.80 Å. Ir4+ is bonded to six O2- atoms to form corner-sharing IrO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (1.98 Å) and two longer (2.08 Å) Ir–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to five equivalent Sr2+ and one Ir4+ atom to form distorted OSr5Ir octahedra that share corners with seventeen OSr5Ir octahedra, edges with eight equivalent OSr5Ir octahedra, and faces with four equivalent OSr4Ir2 octahedra. The corner-sharing octahedra tilt angles range from 0–56°. In the second O2- site, O2- is bonded to four equivalent Sr2+ and two equivalent Ir4+ atoms to form distorted OSr4Ir2 octahedra that share corners with fourteen OSr5Ir octahedra, edges with two equivalent OSr4Ir2 octahedra, and faces with eight OSr5Ir octahedra. The corner-sharing octahedra tilt angles range from 0–56°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr2IrO4 by Materials Project

Sr2IrO4 crystallizes in the tetragonal I4_1/acd space group. The structure is three-dimensional. Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.46–2.77 Å. Ir4+ is bonded to six O2- atoms to form corner-sharing IrO6 octahedra. The corner-sharing octahedral tilt angles are 27°. There are four shorter (2.01 Å) and two longer (2.09 Å) Ir–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sr2+ and two equivalent Ir4+ atoms. In the second O2- site, O2- is bonded to five equivalent Sr2+ and one Ir4+ atom to form a mixture of edge and corner-sharing OSr5Ir octahedra. The corner-sharing octahedra tilt angles range from 0–5°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Strain engineering of the charge and spin-orbital interactions in Sr2IrO4

In the high spin–orbit-coupled Sr 2 IrO 4 , the high sensitivity of the ground state to the details of the local lattice structure shows a large potential for the manipulation of the functional properties by inducing local lattice distortions. We use epitaxial strain to modify the Ir–O bond geometry in Sr 2 IrO 4 and perform momentum-dependent resonant inelastic X-ray scattering (RIXS) at the metal and at the ligand sites to unveil the response of the low-energy elementary excitations. Furthermore, we observe that the pseudospin-wave dispersion for tensile-strained Sr 2 IrO 4 films displays large softening along the [h,0] direction, while along the [h,h] direction it shows hardening. This evolution reveals a renormalization of the magnetic interactions caused by a strain-driven cross-over from anisotropic to isotropic interactions between the magnetic moments. Moreover, we detect dispersive electron–hole pair excitations which shift to lower (higher) energies upon compressive (tensile) strain, manifesting a reduction (increase) in the size of the charge gap. This behavior shows an intimate coupling between charge excitations and lattice distortions in Sr 2 IrO 4 , originating from the modified hopping elements between the t 2g orbitals. Our work highlights the central role played by the lattice degrees of freedom in determining both the pseudospin and charge excitations of Sr 2 IrO 4 and provides valuable information toward the control of the ground state of complex oxides in the presence of high spin–orbit coupling.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Pseudospin-lattice coupling and electric control of the square-lattice iridate Sr2IrO4

Sr 2 IrO 4 is an archetypal spin-orbit-coupled Mott insulator and has been extensively studied in part because of a wide range of predicted states. Limited experimental characterization of these states thus far brings to light the extraordinary susceptibility of the physical properties to the lattice, particularly, the Ir-O-Ir bond angle. Here, we report a microscopic rotation of the IrO 6 octahedra below 50 K measured by single crystal neutron diffraction. Overall, this sharp lattice anomaly provides keys to understanding the anomalous low-temperature physics and a direct confirmation of a crucial role that the Ir-O-Ir bond angle plays in determining the ground state. Indeed, as also demonstrated in this study, applied electric current readily weakens the antiferromagnetic order via the straightening of the Ir-O-Ir bond angle, highlighting that even slight change in the local structure can disproportionately affect the physical properties in the spin-orbit-coupled system.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Emergent interlayer magnetic order via strain-induced orthorhombic distortion in the 5 d Mott insulator Sr 2 IrO 4

In this letter, we report a La 2 CuO 4 -like interlayer antiferromagnetic order in Sr2IrO4 films with large orthorhombic distortion (>1.5%). The biaxial lattice strain in epitaxial heterostructures of Sr 2 IrO 4 /Ca 3 Ru 2 O 7 lowers the crystal symmetry of Sr 2 IrO 4 from tetragonal ($C_4$) to orthorhombic ($C_2$), guiding the Ir $5d J_{text{eff}}$ = 1/2 pseudospin moment parallel to the elongated b axis via magnetic anisotropy. From resonant x-ray scattering experiments, we observed an antiferromagnetic order in the orthorhombic Sr 2 IrO 4 film whose interlayer stacking pattern is inverted from that of the tetragonal Sr 2 IrO 4 crystal. This interlayer stacking is similar to that of the orthorhombic La 2 CuO 4 , implying that the asymmetric interlayer exchange interactions between $\textit{a}$ and $\textit{b}$ directions exceed the anisotropic interlayer pseudodipolar interaction. Our result suggests that strain-induced distortion can provide a delicate knob for tuning the long-range magnetic order in quasi-two-dimensional systems by evoking the competition between the interlayer exchange coupling and the pseudodipolar interaction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗