Crystal growth, structure and magnetic properties of Ca10Cr7O28

Balz, Christian; Lake, B.; Reehuis, M.; Islam, A. T. M. N.; Prokhnenko, O.; Singh, Yogesh; Pattison, Philip; Tóth, S.

doi:10.1088/1361-648x/aa68eb

Cited by 19 publications

(41 citation statements)

References 20 publications

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“…[21]. DC susceptibility, magnetization and heat capacity were measured on single crystals over a range of temperatures and applied magnetic fields.…”

Section: Methodsmentioning

confidence: 99%

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Magnetic Hamiltonian and phase diagram of the quantum spin liquidCa10Cr7O28

et al. 2017

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A spin liquid is a new state of matter with topological order where the spin moments continue to fluctuate coherently down to the lowest temperatures rather than develop static long-range magnetic order as found in conventional magnets. For spin liquid behavior to arise in a material the magnetic Hamiltonian must be "frustrated" where the combination of lattice geometry, interactions and anisotropies gives rise to competing spin arrangements in the ground state. Theoretical Hamiltonians which produce spin liquids are spin ice, the Kitaev honeycomb model and the kagome antiferromagnet. Spin liquid behavior however in real materials is rare because they can only approximate these Hamiltonians and often have weak higher order terms that destroy the spin liquid state. Ca10Cr7O28 is a new quantum spin liquid candidate with magnetic Cr 5+ ions that possess quantum spin number S= 1 /2. The spins are entirely dynamic in the ground state and the excitation spectrum is broad and diffuse as is typical of spinons which are the excitations of a spin liquid. In this paper we determine the Hamiltonian of Ca10Cr7O28 using inelastic neutron scattering under high magnetic field to induce a field polarized paramagnetic ground state and spin-wave excitations that can be fitted to extract the interactions. We further explore the phase diagram by using inelastic neutron scattering and heat capacity measurements and establish the boundaries of the spin liquid phase as a function of magnetic field and temperature. Our results show that Ca10Cr7O28 consists of distorted kagome bilayers with several isotropic ferromagnetic and antiferromagnetic interactions where unexpectedly the ferromagnetic interactions are stronger than the antiferromagnetic ones. This complex Hamiltonian does not correspond to any known spin liquid model and points to new directions in the search for quantum spin liquid behavior. INTRODUCTIONConventional magnets in condensed matter typically develop long-range magnetic order when cooled to low temperatures [1]. Below their ordering temperature the magnetic moments develop a static component which acts as the order parameter for the phase transition and the spin ordering is observable as magnetic Bragg peaks which characterize the type of order. The excitations are usually spin-waves which are collective oscillations of the spins about their ordering directions. The transition can be described by Landau theory where symmetry is broken and the new phase is characterized by a local order parameter [2].It was recently realized that some states of matter are characterized by topological order, rather than by symmetry breaking and a local order parameter [3]. This important discovery promises new, exotic and potentially useful properties that could be of relevance e.g. to information technologies. For example topological order gives rise to coherent states which can be highly robust to the usual perturbations that destroy coherence in ordinary states due to the non-local nature of their correlations.One potential applicati...

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“…[21]. DC susceptibility, magnetization and heat capacity were measured on single crystals over a range of temperatures and applied magnetic fields.…”

Section: Methodsmentioning

confidence: 99%

“…The positions of the magnetic Cr 5+ ions in Ca 10 Cr 7 O 28 are represented in figure 1(a) by the black and gray spheres [21]. They form layers in the ab−plane that are [20] and its supplemental material.)…”

Section: Introduction Of the Modelsmentioning

confidence: 99%

Magnetic Hamiltonian and phase diagram of the quantum spin liquidCa10Cr7O28

et al. 2017

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“…32 In this paper, we address the aforementioned opportunities and challenges in identifying quantum spin liquids based on the compound Ca 10 Cr 7 O 28 . [33][34][35][36][37][38] Particularly, we demonstrate that new heat capacity and single crystal neutron scattering data in conjunction with an effective model for the lowenergy excitations allows an interpretation in terms of emergent spinon degrees of freedom that is remarkably straightforward and consistent. In a previous publication by some of the authors, Ca 10 erties of a quantum spin liquid such as an absence of magnetic long-range order down to at least 19 mK, persistent spin dynamics at low temperatures and a diffuse scattering signal in neutron experiments.…”

Section: Introductionmentioning

confidence: 93%

“…Single crystal samples of Ca 10 Cr 7 O 28 were prepared according to the procedure described in Ref. 35. The heat capacity was measured on two different calorimeters.…”

Section: A Experimental Detailsmentioning

confidence: 99%

Signatures for spinons in the quantum spin liquid candidate Ca10Cr7O28

et al. 2019

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We present new experimental low-temperature heat capacity and detailed dynamical spin-structure factor data for the quantum spin liquid candidate material Ca10Cr7O28. The measured heat capacity shows an almost perfect linear temperature dependence in the range 0.1 K T 0.5 K, reminiscent of fermionic spinon degrees of freedom. The spin structure factor exhibits two energy regimes of strong signal which display rather different but solely diffuse scattering features. We theoretically describe these findings by an effective spinon hopping model which crucially relies on the existence of strong ferromagnetically coupled triangles in the system. Our spinon theory is shown to naturally reproduce the overall weight distribution of the measured spin structure factor. Particularly, we argue that various different observed characteristic properties of the spin structure factor and the heat capacity consistently indicate the existence of a spinon Fermi surface. A closer analysis of the heat capacity at the lowest accessible temperatures hints towards the presence of weak f -wave spinon pairing terms inducing a small partial gap along the Fermi surface (except for discrete nodal Dirac points) and suggesting an overall Z2 quantum spin liquid scenario for Ca10Cr7O28.

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“…Ca 10 Cr 7 O 28 crystallizes in R3c space group [23,24]. There are seven chromium ions with different valences per formula unit, six of which are magnetic Cr 5+ while the remaining one is nonmagnetic Cr 6+ , coordinated by oxygen tetrahedra [24], which are shown in red and orange colors in Fig. 1(a), respectively.…”

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Ultralow-temperature heat transport in the quantum spin liquid candidate Ca10Cr7O28 with a bilayer kagome lattice

Liu

et al. 2018

Phys. Rev. B

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Recently, a novel material with bilayer kagome lattice Ca10Cr7O28 was proposed to be a gapless quantum spin liquid, due to the lack of long-range magnetic order and the observation of broad diffuse excitations. Here, we present the ultralow-temperature thermal conductivity measurements on single crystals of Ca10Cr7O28 to detect its low-lying magnetic excitations. At finite temperatures, with increasing the magnetic fields, the thermal conductivity exhibits a clear dip around 6 T, which may correspond to a crossover in the magnetic ground state. At the zero-temperature limit, no residual linear term is found at any fields, indicating the absence of gapless itinerant fermionic excitations. Therefore, if the spinons do exist, they are either localized or gapped. In the gapped case, the fitting of our data gives a small gap ∆ ∼ 0.27(2) K. These results put strong constraints on the theoretical description of the ground state in this quantum spin liquid candidate. arXiv:1803.03515v1 [cond-mat.str-el]

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Crystal growth, structure and magnetic properties of Ca₁₀Cr₇O₂₈

Cited by 19 publications

References 20 publications

Magnetic Hamiltonian and phase diagram of the quantum spin liquidCa10Cr7O28

Magnetic Hamiltonian and phase diagram of the quantum spin liquidCa10Cr7O28

Signatures for spinons in the quantum spin liquid candidate Ca10Cr7O28

Ultralow-temperature heat transport in the quantum spin liquid candidate Ca10Cr7O28 with a bilayer kagome lattice

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