Unconventional magnetism in the spin-orbit driven Mott insulators Ba3MIr2O9 (M=Sc,Y)

Abstract

We have carried out detailed bulk and local probe studies on the hexagonal oxides Ba3MIr2O9 (M=Sc,Y) where Ir is expected to have a fractional oxidation state of +4.5. In the structure, Ir-Ir dimers are arranged in an edge shared triangular network parallel to the ab plane. Whereas only weak anomalies are evident in the susceptibility data, clearer anomalies are present in the heat capacity data. Our 45Sc nuclear magnetic resonance (NMR) lineshape (first order quadrupole split) is symmetric at room temperature but becomes progressively asymmetric with decreasing temperatures. This is suggestive of distortions in the structure which could arise from progressive tilt/rotation of the IrO6 octahedra with a decrease in temperature T. The 45Sc NMR spectral weight shifts near the reference frequency with decreasing T indicating the development of magnetic singlet regions. Around 10K, a significant change in the spectrum takes place with a large intensity appearing near the reference frequency but with the spectrum remaining multi-peak. It appears from our 45Sc NMR data that in Ba3ScIr2O9 significant disorder is still present below 10K. In the case of Ba3YIr2O9, the 89Y NMR spectral lines are asymmetric at high temperatures but become nearly symmetric (single magnetic environment) below T~70K. Our 89Y spectra and T1 measurements confirm the onset of long range ordering (LRO) from a bulk of the sample at 4K in this compound. Our results suggest that Ba3YIr2O9 might be structurally distorted at room temperature (via, for example, tilt/rotations of the IrO6 octahedra) but becomes progressively a regular triangular lattice with decreasing T. The effective magnetic moments and magnetic entropy changes are strongly reduced in Ba3YIr2O9 as compared to those expected for a S=1/2 system. Similar effects have been found in other iridates which naturally have strong spin-orbit coupling (SOC).

arXiv comment9 pages, 10 figures, to appear in PRB

References in corpus (25)

• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Kitaev-Heisenberg Model on Honeycomb Lattice: Possible Exotic Phases in Iridium Oxides $A_2$IrO${}_3$
• Quantum Hall effects in a Weyl Semi-Metal: possible application in pyrochlore Iridates
• To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
• Spin-Liquid State in the S = 1/2 Hyperkagome Antiferromagnet Na4Ir3O8
• Twisted Hubbard Model for Sr2IrO4: Magnetism and Possible High Temperature Superconductivity
• Exotic phases induced by strong spin-orbit coupling in ordered double perovskites
• Excitonic Magnetism in Van Vleck-type d^4 Mott Insulators
• Crystal field splitting and correlation effect on the electronic structure of A2IrO3
• Unconventional superconductivity and antiferromagnetic quantum critical behavior in the isovalent-doped BaFe2(As1-xPx)2
• Possible valence-bond condensation in the frustrated cluster magnet LiZn2Mo3O8
• ^{63}Cu, ^{35}Cl, and ^{1}H NMR in the S=1/2 Kagomé Lattice ZnCu_{3}(OH)_{6}Cl_{2}
• NMR and LDA evidence for spiral magnetic order in the chain cuprate LiCu2O2
• Magnetic properties of the geometrically frustrated S=1/2 antiferromagnets, La2LiMoO6 and Ba2YMoO6, with the B-site ordered double perovskite structure: Evidence for a Collective Spin Singlet Ground State
• Spin liquid behaviour in Jeff=1/2 triangular lattice Ba3IrTi2O9
• Molecular Quantum Magnetism in LiZn2Mo3O8
• Absence of static phase separation in the high-Tc cuprate $YB{a}_{2}C{u}_3{O}_{6+y}$
• Supplementary material for "Impurity-induced magnetic order in low dimensional spin gapped materials"
• Study of one-dimensional nature of (Sr,Ba)_2Cu(PO_4)_2 and BaCuP_2O_7 via 31P NMR
• Evolution of Magnetism in Single-Crystal Honeycomb Iridates
• Emergent honeycomb lattice in LiZn2Mo3O8
• Spin liquid close to a quantum critical point in Na${}_4$Ir${}_3$O${}_8$
• Singlet Ground State of the Quantum Antiferromagnet Ba3CuSb2O9
• Possible spin-orbit driven spin-liquid ground state in the double perovskite phase of Ba3YIr2O9
• Magnetic behavior of Ba_{3}Cu_{3}Sc_{4}O_{12}

Cited by in corpus (9)

• Models and Materials for Generalized Kitaev Magnetism
• Coulomb Correlations in 4d and 5d Oxides from First Principles - or How Spin-Orbit Materials choose their Effective Orbital Degeneracies
• Persistent low-temperature spin dynamics in the mixed-valence iridate Ba${}_3$InIr${}_2$O${}_9$
• Quasimolecular electronic structure of the spin-liquid candidate Ba${}_3$InIr${}_2$O${}_9$
• RIXS interferometry and the role of disorder in the quantum magnet Ba${}_3$Ti${}_{3-x}$Ir${}_x$O${}_9$
• Soft and anisotropic local moments in 4$d$ and 5$d$ mixed-valence M${}_2$O${}_9$ dimers
• Novel quantum spin liquid ground state in the trimer rhodate Ba${}_4$NbRh${}_3$O${}_{12}$
• Gapless dynamic magnetic ground state in the charge-gapped trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$
• Orbital-Selective Spin-Orbit Mott Insulator in Fractional Valence Iridate La${}_3$Ir${}_3$O${}_{11}$