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DOE OSTI · 1892414

Spin-orbit coupling controlled ground states in the double perovskite iridates $\textit{A}_2\textit{B}$IrO$_6$ ($\textit{A}$ = Ba, Sr; $\textit{B}$ = Lu, Sc)

Aczel, Adam A.·Chen, Q.·Clancy, J. P.·dela Cruz, Clarina R.·Reig-i-Plessis, D.·MacDougall, G. J.·Pollock, C. J.·Upton, M. H.·Williams, Travis J.·LaManna, N.·Carlo, J. P.·Beare, J.·Luke, G. M.·Zhou, H. D.
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Abstract

Iridates with the 5$d^4$ electronic configuration have attracted recent interest due to reports of magnetically ordered ground states despite longstanding expectations that their strong spin-orbit coupling would generate a $\textit{J}$ = 0 electronic ground state for each Ir 5+ ion. The major focus of prior research has been on the double perovskite iridates Ba 2 YIrO 6 and Sr 2 YIrO 6 , where the nature of the ground states (i.e., ordered vs nonmagnetic) is still controversial. Here, in this work, we present neutron powder diffraction, high-energy-resolution fluorescence-detected x-ray absorption spectroscopy (HERFD-XAS), resonant inelastic x-ray scattering (RIXS), magnetic susceptibility, and muon spin relaxation data on the related double perovskite iridates Ba 2 LuIrO 6 , Sr 2 LuIrO 6 , Ba 2 ScIrO 6 , and Sr 2 ScIrO 6 that enable us to gain a general understanding of the electronic and magnetic properties for this family of materials. Our HERFD-XAS and RIXS measurements establish $\textit{J}$ = 0 electronic ground states for the Ir 5+ ions in all cases, with similar values for Hund's coupling $J_H$ and the spin-orbit coupling constant $λ_{\text{SOC}}$. Our bulk susceptibility and muon spin relaxation data find no evidence for long-range magnetic order or spin freezing, but they do exhibit weak magnetic signals that are consistent with extrinsic local moments. Our results indicate that the large $λ_{\text{SOC}}$ is the key driving force behind the electronic and magnetic ground states realized in the $5d^4$ double perovskite iridates, which agrees well with conventional wisdom.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRYdilution refrigeratormagnetic susceptibilitymagnetismmuon spin relaxation & rotationneutron diffractionstructural propertiessusceptibility measurements

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Aczel, Adam A., Chen, Q., Clancy, J. P., dela Cruz, Clarina R., Reig-i-Plessis, D., MacDougall, G. J., Pollock, C. J., Upton, M. H., Williams, Travis J., LaManna, N., Carlo, J. P., Beare, J., Luke, G. M., Zhou, H. D.. 2022-09-19. Spin-orbit coupling controlled ground states in the double perovskite iridates $\textit{A}_2\textit{B}$IrO$_6$ ($\textit{A}$ = Ba, Sr; $\textit{B}$ = Lu, Sc). https://doi.org/10.1103/physrevmaterials.6.094409

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