Temperature-dependent spin gap and singlet ground state in BaCuSi2O6

TL;DR

This study investigates the temperature-dependent magnetic properties of BaCuSi2O6, revealing a spin gap and singlet ground state consistent with a Heisenberg model, using neutron scattering and magnetic measurements.

Contribution

It provides new insights into the temperature dependence of spin excitations in a quasi-2D antiferromagnet with a bilayer structure.

Findings

Temperature-dependent dispersion in gap modes observed

Magnetic excitations resemble magneto-excitons

Results align with a Heisenberg Hamiltonian model

Abstract

Bulk magnetic measurements and inelastic neutron scattering were used to investigate the spin-singlet ground state and magnetic gap excitations in BaCuSi2O6, a quasi-2-dimensional antiferromagnet with a bilayer structure. The results are well described by a model based on weakly interacting antiferromagnetic dimers. A strongly temperature-dependent dispersion in the gap modes was found. We suggest that the observed excitations are analogous to magneto-excitons in light rare-earth compounds, but are an intrinsic property of a simple Heisenberg Hamiltonian for the S=1/2 magnetic bilayer.