Polarized-neutron investigation of magnetic ordering and spin dynamics in BaCo${}_2$(AsO${}_4$)${}_2$ frustrated honeycomb-lattice magnet

Abstract

The magnetic properties of the cobaltite {\BCAO}, a good realization of the quasi two-dimensional frustrated honeycomb-lattice system with strong planar anisotropy, have been reinvestigated by means of spherical neutron polarimetry with CRYOPAD. From accurate measurements of polarization matrices both on elastic and inelastic contributions as a function of the scattering vector {\bf{Q}}, we have been able to determine the low-temperature magnetic structure of {\BCAO} and reveal its puzzling in-plane spin dynamics. Surprisingly, the ground-state structure (described by an incommensurate propagation vector ${\mathbf{k}}_1=(k_x,0,k_z$), with $k_x=0.270\pm 0.005$ and $k_z\approx -1.31$) appears to be a quasi-collinear structure, and not a simple helix, as previously determined. In addition, our results have revealed the existence of a non-negligible out-of-plane moment component $\approx 0.25{\mu }_B$/Co${}^{2+}$, representing about 10\% of the in-plane component, as demonstrated by the presence of finite off-diagonal elements $P_{yz}$ and $P_{zy}$ of the polarization matrix, both on elastic and inelastic magnetic contributions. Despite a clear evidence of the existence of a slightly inelastic contribution of structural origin superimposed to the magnetic excitations at the scattering vectors $\mathbf{Q}=(0.27,0,3.1)$ and $\mathbf{Q}=(0.73,0,0.8)$ (energy transfer $\Delta E\approx 2.3$ meV), no strong inelastic nuclear-magnetic interference terms could be detected so far, meaning that the nuclear and magnetic degrees of freedom have very weak cross-correlations. The strong inelastic $P_{yz}$ and $P_{zy}$ matrix elements can be understood by assuming that the magnetic excitations in {\BCAO} are spin waves associated with trivial anisotropic precessions of the magnetic moments involved in the canted incommensurate structure.

43 pages, 16 figures

References in corpus (4)

• Spin-gap phase of a quantum spin system on a honeycomb lattice
• The frustrated spin-$\frac{1}{2}$ $J_1$--$J_2$ isotropic $XY$ model on the honeycomb lattice
• Phase diagram of a frustrated spin-$\frac{1}{2}$ $J_1$--$J_2$ $XXZ$ model on the honeycomb lattice
• Kosterlitz-Thouless Phase Transition of the ANNNI model in Two Dimensions

Cited by in corpus (29)

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• Weak-field induced nonmagnetic state in a Co-based honeycomb
• Geometrical frustration versus Kitaev interactions in BaCo${}_2$(AsO${}_4$)${}_2$
• A magnetic continuum observed by terahertz spectroscopy in a quantum spin liquid candidate BaCo${}_2$(AsO${}_4$)${}_2$
• XY magnetism, Kitaev exchange, and long-range frustration in the $J_{\mathrm{eff}}=1/2$ honeycomb cobaltates
• Magnetic Couplings in Edge-Sharing High-Spin $d^7$ Compounds
• Ab initio guided minimal model for the "Kitaev" material BaCo${}_2$(AsO${}_4$)${}_2$: Importance of direct hopping, third-neighbor exchange and quantum fluctuations
• Magnetic excitations of the field induced states in BaCo2(AsO4)2 probed by time-domain terahertz spectroscopy
• Quantum Phases in the Honeycomb-Lattice $J_1$--$J_3$ Ferro-Antiferromagnetic Model
• Proximate Dirac spin liquid in honeycomb lattice $J_1$-$J_3$ XXZ model: Numerical study and application to cobaltates
• Spin vestigial orders in extended Heisenberg-Kitaev models near hidden SU(2) points: Application to Na${}_2$Co${}_2$TeO${}_6$
• Comparative Raman Scattering Study of Crystal Field Excitations in Co-based Quantum Magnets
• Single-crystal study of the honeycomb XXZ magnet BaCo${}_2$(PO${}_4$)${}_2$ in magnetic fields
• Spin Waves and Dirac Magnons in a Honeycomb Lattice Zig-zag Antiferromagnet BaNi2(AsO4)2
• BaCo${}_2$(AsO${}_4$)${}_2$: Strong Kitaev, After All
• On the multi-$\mathbf{q}$ characteristics of magnetic ground states of honeycomb cobalt oxides
• Hydrostatic pressure effect on Co-based honeycomb magnet BaCo2(AsO4)2
• Intermediate field-induced phase of the honeycomb magnet BaCo${}_2$(AsO${}_4$)${}_2$
• Proximity-induced sequence of field transitions in Kitaev candidate BaCo${}_2$(AsO${}_4$)${}_2$
• Chemical tuning of a honeycomb magnet through a critical point
• Spin-orbit entangled moments and magnetic exchange interactions in cobalt-based honeycomb magnets BaCo${}_2$($X$O${}_4$)${}_2$ ($X$ = P, As, Sb)
• Ground state and magnetic transitions of the orthorhombic antiferromagnet CaCo${}_2$TeO${}_6$
• Bond-dependent interactions and ill-ordered state in the honeycomb cobaltate BaCo${}_2$(AsO${}_4$)${}_2$
• Impact of gapped spin-orbit excitons on low energy pseudospin exchange interactions
• Scaling behavior and giant field-enhancement of the thermal conductivity in the honeycomb antiferromagnet BaCo2(AsO4)2
• Demystifying quantum escapism on the honeycomb lattice
• Order-by-disorder from Schwinger bosons in a frustrated honeycomb ferromagnet
• Trigonal distortion in the Kitaev candidate honeycomb magnet BaCo2(AsO4)2
• Crystalline water intercalation into the Kitaev honeycomb cobaltate Na${}_2$Co${}_2$TeO${}_6$