Pressure Tuning of the Spin-Orbit Coupled Ground State inSr2IrO4

Abstract

X-ray absorption spectroscopy studies of the magnetic-insulating ground state of Sr2IrO4 at ambient pressure show a clear deviation from a strong spin-orbit (SO) limit J(eff)=1/2 state, a result of local exchange interactions and a nonzero tetragonal crystal field mixing SO split J(eff)=1/2, 3/2 states. X-ray magnetic circular dichroism measurements in a diamond anvil cell show a magnetic transition at a pressure of ∼17 GPa, where the "weak" ferromagnetic moment is quenched despite transport measurements showing insulating behavior to at least 40 GPa. The magnetic transition has implications for the origin of the insulating gap and the nature of exchange interactions in this SO coupled system. The expectation value of the angular part of the SO interaction, <L·S>, extrapolates to zero at ∼80-90 GPa where an increased bandwidth strongly mixes J(eff)=1/2, 3/2 states and SO interactions no longer dominate the electronic ground state of Sr2IrO4.

Fragility of ferromagnetic double exchange interactions and pressure tuning of magnetism in3d−5ddouble perovskiteSr2FeOsO6

“…We obtain a BR value of 2.6(1) for both compounds, corresponding to L · S = 0.99h 2 for the unoccupied 5d electron states. Even though the spinorbit interaction strength, ζ, used in the calculations is comparable to that in the iridates, the spin-orbit coupling in osmates is significantly reduced with respect to these compounds [30][31][32] . While the S-O interaction is still significant, Os cannot be described in the strong spin-orbit coupling limit where 3 electrons would occupy j ef f = 3/2 states 30-32 as this would yield L · S = 9ζ/10Dq + 3/2 = 2.66h 2 using the values from the cluster calculation.…”

Noncollinear versus collinear description of the Ir-based one-t2g-hole perovskite-related compounds:SrIrO3andSr2Lado1, Pardo2 2015Phys. Rev. B12580View full textAdd to dashboardCite

“…One could think that this has to do with the huge tetragonal distortion of the octahedral environment. 17 However, at large tensile strains, such as the case of setting a to that of MgAl 2 O 4 , the in-plane Ir-O distance becomes equal (only 0.3 % difference) to the out-of-plane metal-anion bond length. Thus, the reason behind this unmixing does not have to do with the on-site energies of the different t 2g levels that are split by the oxygen crystal field.…”

“…This has been described as a pure j ef f = 1/2 state 8, 13 or as a mixture due to contributions from both j ef f = 3/2 and e g states. [14][15][16][17] To elucidate this issue, several iridates have been measured via different spectroscopic techniques, revealing that the L z /S z ratio can be different 18,19 from the expected value of 4 that would occur for the pure j ef f = 1/2 state. 13 At present it is not clear what the actual size of the different parameters involved in determining the electronic structure should be (Hubbard U, spin-orbit coupling strength, band width, etc.…”

Spin-orbit tuned metal-insulator transitions in single-crystal Sr2Ir1−xRhxQi1, Korneta2, Li3 et al. 2012Phys. Rev. BSelf Cite116101440View full textAdd to dashboardCite

“…The size of the single crystals is as large as 1.0 x 1.0 x 0.2 cm 3 (see Fig.1d). 4 were determined using a Nonius Kappa CCD X-ray diffractometer at 90 K and 295 K. Structures were refined by full-matrix least-squares using the SHELX-97 programs [27]. The standard deviations of all lattice parameters and interatomic distances are smaller than 0.1%.…”