Ground state and intrinsic susceptibility of the kagome antiferromagnet vesignieite as seen by<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>51</mml:mn></mml:msup></mml:math>V NMR

Quilliam, J. A.; Bert, F.; Colman, R. H.; Boldrin, D.; Wills, A. S.; Mendels, P.

doi:10.1103/physrevb.84.180401

Cited by 55 publications

(84 citation statements)

References 33 publications

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“…The tendency to magnetic order in paratacamites may be induced by interplane couplings through Cu defect spins at the Zn site between the kagomé layers, as well as the likely presence of a sizable Dzyaloshinsky-Moriya term. On the other hand, the nearly undistorted kagomé compound vesignieite, BaCu 3 V 2 O 8 (OH) 2 , has recently been reported to show a peculiar transition at 9 K to a partly frozen state with persisting spin dynamics 6,7 , despite no order being found in previous studies 5 . It is suggested that this order occurs owing to a large Dzyaloshinsky-Moriya interaction within the kagomé plane 6,7 .…”

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confidence: 96%

Orbital switching in a frustrated magnet

et al. 2012

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The orbital is one of the four fundamental degrees of freedom in a solid, besides spin, charge and lattice. In transition metal compounds, it is usually the d orbitals which play deciding roles in determining the crystallographic and physical properties. Here we report the discovery of a unique structural transition in single crystals of the spin-1/2 quasi-kagomé antiferromagnet volborthite, Cu 3 V 2 o 7 (oH) 2 ·2H 2 o, whereby the unpaired electron 'switches' from one d orbital to another upon cooling. This is not a conventional orbital order-disorder transition, but rather an orbital switching that has not previously been observed. The structural transition is found to profoundly affect the magnetic properties of volborthite, because magnetic interactions between Cu spins in the kagomé lattice are considerably modified by the orbital switching. This finding provides us with an interesting example to illustrate the intimate interplay between the orbital degree of freedom and competing magnetic interactions in a frustrated magnet.

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confidence: 96%

Orbital switching in a frustrated magnet

et al. 2012

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“…In the case of BaCu 3 V 2 O 8 (OH) 2 , an inhomogeneous magnetic order has been detected through NMR measurements around 9 K, below which the unwanted Curie tail grows rapidly. 15,16 We have discovered the absense of magnetic long range order in a hexagonal lattice of Ru 5+ dimers in Ba 3 ZnRu 2 O 9 down to 37 mK, where neither Curie tail nor glassy behavior is detected. The magnetic specific heat shows no anomaly below 80 K, and is found to be linear in temperature below around 5 K. These thermodynamic measurements suggest a spin-liquid like ground state in this oxide.…”

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Absence of Magnetic Long Range Order in Ba₃ZnRu₂O₉: A Spin-Liquid Candidate in the S = 3/2 Dimer Lattice

et al. 2017

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We have discovered a novel candidate for a spin liquid state in a ruthenium oxide composed of dimers of S = 3/2 spins of Ru 5+ , Ba 3 ZnRu 2 O 9 . This compound lacks a long range order down to 37 mK, which is a temperature 5000-times lower than the magnetic interaction scale of around 200 K. Partial substitution for Zn can continuously vary the magnetic ground state from an antiferromagnetic order to a spin-gapped state through the liquid state. This indicates that the spin-liquid state emerges from a delicate balance of inter-and intra-dimer interactions, and the spin state of the dimer plays a vital role. This unique feature should realize a new type of quantum magnetism.Since Anderson proposed the idea of a quantum spin liquid as a possible ground state for a spin-half (S = 1/2) antiferromagnetic triangular lattice 1 with a suppressed longrange magnetic ordering due to geometrical frustration and quantum fluctuations of interacting spins, researchers have sought this state of quantum matter. 2 A quantum spin liquid should possess a ground state consisting of highly entangled singlet-spin pairs and exotic excited states called spinons. 3,4 Although several candidates have been reported experimentally, none has been confirmed. Organic candidates consist of ill-defined localized magnetic moments where the magnetic exchange interaction is comparable to the charge gap. [5][6][7] On the other hand, inorganic candidates suffer from unwanted disorder/impurity/nonstoichiometry. Na 4 Ir 3 O 8 8 shows a spin-glass-like transition near 6-7 K, 9, 10 whereas ZnCu 3 (OH) 6 Cl 2 11 and Ba 3 CuSb 2 O 9 12 include a considerable intermixture of cations. BaCu 3 V 2 O 8 (OH) 2 13 and 6H-B Ba 3 NiSb 2 O 9 14 have a substantial low-temperature Curie tail due to unwanted impurities. In the case of BaCu 3 V 2 O 8 (OH) 2 , an inhomogeneous magnetic order has been detected through NMR measurements around 9 K, below which the unwanted Curie tail grows rapidly. 15,16 We have discovered the absense of magnetic long range order in a hexagonal lattice of Ru 5+ dimers in Ba 3 ZnRu 2 O 9 down to 37 mK, where neither Curie tail nor glassy behavior is detected. The magnetic specific heat shows no anomaly below 80 K, and is found to be linear in temperature below around 5 K. These thermodynamic measurements suggest a spin-liquid like ground state in this oxide. The Ru 5+ ion acts as a well-localized S = 3/2 spin, and the spin liquid is totally unprecedented in such a large spin.

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“…This certainly affects the Ir 4+ environments and leads to a distribution of magnetic interactions on the hyperkagome lattice, especially if interactions are dominantly due to direct exchange as argued in many papers [39]. Deviations to equilateral interaction triangles have always led to transitions at T J such as observed in Volborthite [40] and Vesignieite [41,42] kagome-based compounds. Digging out why a distribution of interactions could lead to such a weak or no signature in χ and C/T respectively should be addressed theoretically which may help discriminate between models proposed for this iridate.…”

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Frozen State and Spin Liquid Physics inNa4Ir3O8: An

Ac¹,

Bert²,

Jc³

et al. 2015

Phys. Rev. Lett.

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Na4Ir3O8 is a unique case of a hyperkagome 3D corner sharing triangular lattice which can be decorated with quantum spins. It has spurred a lot of theoretical interest as a spin liquid candidate. We present a comprehensive set of NMR data taken on both the 23 Na and 17 O sites. We show that disordered magnetic freezing of all Ir sites sets in below T f ∼ 7 K, well below J = 300 K, with a drastic slowing down of fluctuations to a static state revealed by our T1 measurements. Above typically 2 T f , physical properties are relevant to the spin liquid state induced by this exotic geometry. While the shift data shows that the susceptibility levels off below 80 K, 1/T1 has little variation from 300 K to 2 T f . We discuss the implication of our results in the context of published experimental and theoretical work.Geometric frustration has long been known as an essential ingredient to stabilize a quantum spin liquid (QSL) state in more than one dimension (1D) [1,2] [10], and organic compounds which are driven by proximity to a Mott transition [11,12].Currently, Na 4 Ir 3 O 8 is one of the most compelling frustrated QSL candidate in three-dimensions (3D) [13] where Ir 4+ ions with effective J eff = 1 2 form a cornersharing lattice of triangles named "hyperkagome" [14]. Strong spin-orbit coupling, SOC, has been identified as an important ingredient in the Hamiltonian. Several possible theoretical scenarios have been proposed thus far, including a classical long-ranged order-by-disorder 120 o coplanar ground state [15] which in the quantum limit melts into a gapped QSL [16] and a gapless QSL [17,18]. More generally, iridates appear as an ideal playground for the study of novel physics governed by strong SOC in competition with Coulomb repulsion, crystal field effects, and inter-site hopping. This has led theorists to promote, for example, the Heisenberg-Kitaev model [19] and the spin-orbit Mott insulator [20]. Na 4 Ir 3 O 8 also appears to be close to an insulator-metal transition [21][22][23][24][25] and weak Mottness has been proposed as a possible scenario for a spin-liquid ground state [26,27], like in the case of organic triangular spin-liquids [12].The macroscopic susceptibility, χ, is typical of J eff = 1 2 moments with antiferromagnetic interactions J ∼ 300 K [14,28]. Heat capacity, C, shows no sign of a bulk transition and has two remarkable features: at 24 K ∼ J/10 a broad maximum and at low temperatures C = γT + βT n where 2 < n < 3 [14,21]. Both χ and C suggest the presence of a gapless ground state [17,18]. Magnetocaloric measurements suggest a quantum critical behavior in zero-field [21]. Although no signs of a bulk transition exist, there is a small splitting of the field-cooled (FC) and zero field-cooled (ZFC) magnetization at T ∼ 6 K [29]. Initially, this splitting was proposed to be associated with a ∼ 1% defect or impurity term [14,21], but recent µSR measurements [29] suggest quasi-static short range spin correlations appear below T = 6 K. Probing the role of these defects on the physics of this compo...

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Ground state and intrinsic susceptibility of the kagome antiferromagnet vesignieite as seen by51V NMR

Cited by 55 publications

References 33 publications

Orbital switching in a frustrated magnet

Orbital switching in a frustrated magnet

Absence of Magnetic Long Range Order in Ba₃ZnRu₂O₉: A Spin-Liquid Candidate in the S = 3/2 Dimer Lattice

Frozen State and Spin Liquid Physics inNa4Ir3O8: An

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Ground state and intrinsic susceptibility of the kagome antiferromagnet vesignieite as seen by51V NMR

Cited by 55 publications

References 33 publications

Orbital switching in a frustrated magnet

Orbital switching in a frustrated magnet

Absence of Magnetic Long Range Order in Ba3ZnRu2O9: A Spin-Liquid Candidate in the S = 3/2 Dimer Lattice

Frozen State and Spin Liquid Physics inNa4Ir3O8: An

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Product

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Absence of Magnetic Long Range Order in Ba₃ZnRu₂O₉: A Spin-Liquid Candidate in the S = 3/2 Dimer Lattice