We report the neutron scattering results for magnetic orderings and excitations in ${\mathrm{Ba}}_2{\mathrm{CoTeO}}_6$ composed of two subsystems, A and B, which are described as an $S=1/2$ triangular Heisenberg-like antiferromagnet and a frustrated honeycomb Ising-like antiferromagnet, respectively. We found that the excitation spectra of both subsystems are well separated and independent of each other. Stripy ordering of Ising-like subsystem B was confirmed below $T_{\mathrm{N}1}=12.0\mathrm{K}$, whereas the elastic scattering for subsystem A displays sharp streaks along $(1/3,1/3,L)$ and $(2/3,2/3,L)$ at 0.30 K ($\ll T_{\mathrm{N}2}=3.0\mathrm{K}$). These findings reveal that subsystems A and B are almost perfectly decoupled. The excitation spectrum of subsystem A is composed of two single-magnon branches with rotonlike minima at the $M$ point and a clearly structured intense continuum, which is similarly observed in ${\mathrm{Ba}}_3{\mathrm{CoSb}}_2{\mathrm{O}}_9$. Dispersion curves for subsystem B can be described by linear spin wave theory within the third-neighbor exchange interaction.

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• Frustrated magnetism
• Magnetic interactions
• Magnons
• Spinon
• 2-dimensional systems
• Antiferromagnets
• Honeycomb lattice
• Single crystal materials
• Inelastic neutron scattering
• Neutron diffraction
• Neutron scattering