Soft and anisotropic local moments in 4$d$ and 5$d$ mixed-valence M${}_2$O${}_9$ dimers

Abstract

We investigate via exact diagonalization of finite clusters the electronic structure and magnetism of M${}_2$O${}_9$ dimers in the mixed-valence hexagonal perovskites A${}_3$B'M${}_2$O${}_9$ for various different fillings of 4$d$ and 5$d$ transition-metal M ions. We find that the magnetic moments of such dimers are determined by a subtle interplay of spin-orbit coupling, Hund's coupling, and Coulomb repulsion, as well as the electron filling of the M ions. Most importantly, the magnetic moments are anisotropic and temperature-dependent. This behavior is a result of spin-orbit coupling, magnetic field effects, and the existence of several nearly-degenerate electronic configurations whose proximity allows occupation of excited states already at room temperature. This analysis is consistent with experimental susceptibility measurements for a variety of dimer-based materials. Furthermore, we perform a survey of A${}_3$B'M${}_2$O${}_9$ materials and propose ground-state phase diagrams for the experimentally relevant M fillings of $d^{4.5}$, $d^{3.5}$ and $d^{2.5}$. Finally, our results show that the usually applied Curie-Weiss law with a constant magnetic moment cannot be used in these spin-orbit-coupled materials.

References in corpus (23)

• Correlated quantum phenomena in the strong spin-orbit regime
• Proximate Kitaev Quantum Spin Liquid Behaviour in α-RuCl${}_3$
• Spin-Orbit Physics Giving Rise to Novel Phases in Correlated Systems: Iridates and Related Materials
• Models and Materials for Generalized Kitaev Magnetism
• Challenges in Design of Kitaev Materials: Magnetic Interactions from Competing Energy Scales
• Ab initio analysis of the tight-binding parameters and magnetic interactions in Na2IrO3
• The Challenge of Spin-Orbit-Tuned Ground States in Iridates
• Recent progress on correlated electron systems with strong spin-orbit coupling
• Covalent bonds against magnetism in transition metal compounds
• Spin-orbital liquid state assisted by singlet-triplet excitation in $J=0$ ground state of Ba${}_3$ZnIr${}_2$O${}_9$
• Spin--orbital interaction for face-sharing octahedra: Realization of a highly symmetric SU(4) model
• Orbital-dependent singlet dimers and orbital-selective Peierls transitions in transition metal compounds
• Role of local geometry in spin and orbital structure of transition metal compounds
• Resonant inelastic x-ray incarnation of Young's double-slit experiment
• Electronic excitations in the edge-shared relativistic Mott insulator: Na${}_2$IrO${}_3$
• J-freezing and Hund's rules in spin-orbit-coupled multiorbital Hubbard models
• Persistent low-temperature spin dynamics in the mixed-valence iridate Ba${}_3$InIr${}_2$O${}_9$
• Charge order at the frontier between the molecular and solid states in Ba3NaRu2O9
• Frustrated spin-1/2 molecular magnetism in the mixed-valence antiferromagnets Ba3MRu2O9 (M = In, Y, Lu)
• Hopping induced ground-state magnetism in 6H perovskite iridates
• Ba${}_3$M${}_x$Ti${}_{3-x}$O${}_9$(M = Ir, Rh): A family of 5\textit{\textcolor{black}{d}}/4\textit{\textcolor{black}{d}}-based, diluted quantum spin liquids
• Unconventional magnetism in the spin-orbit driven Mott insulators Ba3MIr2O9 (M=Sc,Y)
• Realization of the orbital-selective Mott state at the molecular level in Ba${}_3$LaRu${}_2$O${}_9$

Cited by in corpus (4)

• Modified Curie-Weiss Law for $j_{\mathrm{eff}}$ Magnets
• Quasimolecular electronic structure of the spin-liquid candidate Ba${}_3$InIr${}_2$O${}_9$
• Quasimolecular $J_{\mathrm{tet}}$=3/2 moments in the cluster Mott insulator GaTa${}_4$Se${}_8$
• Quasimolecular electronic structure of the trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$