Frustrated magnetic interactions in an S=3/2 bilayer honeycomb lattice compound Bi3Mn4O12(NO3)

TL;DR

This study investigates magnetic excitations in a bilayer honeycomb lattice compound, revealing that intrabilayer frustration, rather than in-plane interactions, leads to a disordered ground state, with experimental results aligning with theoretical predictions.

Contribution

It provides experimental evidence for the role of intrabilayer frustration in preventing magnetic order in an S=3/2 honeycomb lattice compound, confirming theoretical models.

Findings

Broad magnetic excitations at ambient field

Development of excitation gaps under magnetic field

Intralayer interactions are consistent with ab initio calculations

Abstract

Inelastic neutron scattering study has been performed in an S=3/2 bilayer honeycomb lattice compound Bi3Mn4O12(NO3) at ambient and high magnetic fields. Relatively broad and monotonically dispersive magnetic excitations were observed at ambient field, where no long range magnetic order exists. In the magnetic field-induced long-range ordered state at 10 T, the magnetic dispersions become slightly more intense, albeit still broad as in the disordered state, and two excitation gaps, probably originating from an easy-plane magnetic anisotropy and intrabilayer interactions, develop. Analyzing the magnetic dispersions using the linear spin-wave theory, we estimated the intraplane and intrabilayer magnetic interactions, which are almost consistent with those determined by ab initio density functional theory calculations [M. Alaei et al., Phys. Rev. B 96, 140404(R) (2017)], except the 3rd and 4th neighbor intrabilayer interactions. Most importantly, as predicted by the theory, there is no significant frustration in the honeycomb plane but frustrating intrabilayer interactions probably give rise to the disordered ground state.