Spin-liquid-like state in pure and Mn-doped TbInO3 with a nearly triangular lattice

Inelastic neutron scattering studies in single crystals of ${\mathrm{TbInO}}₃$ and ${\mathrm{TbIn}}_0.95{\mathrm{Mn}}_0.05{\mathrm{O}}₃$ with nearly triangular antiferromagnetic lattice are reported. At low energies, a broad and apparently gapless continuum of magnetic excitations, located at the triangular lattice (TL) Brillouin zone boundary, is observed. The data are well described by the uncorrelated nearest-neighbor valence bonds model. At higher energies, a broad excitation branch dispersing from the TL zone boundary is observed. No signs of static magnetic order are found down to the temperatures two orders of magnitude smaller than the effective interaction energy. The fluctuating magnetic moment exceeds two-thirds of the ${\mathrm{Tb}}³⁺$ free-ion value and is confined to the TL plane. These observations are consistent with a TL-based spin liquid state in ${\mathrm{TbInO}}₃$.