Observation of the Haldane Gap in Y_2BaNiO_5 Single Crystal

概要

論文の詳細を見る
Magnetization measurement and inelastic neutron scattering have been performed on a single crystal of a new Haldane system Y_2BaNiO_5. Magnetic susceptibility shows a weak anisotropy and decreases as temperature decreases, reflecting the singlet ground state at low temperature. The energy gaps were found to be Δ ⫽/k_B = 118K and Δ⊥ /k_B=104K, parallel and perpendicular to the chain, respectively. Using inelastic neutron scattering magnetic excitations along the chain (a^*-) and perpendicular (c^*-) directions up to 30 meV energy transfer are studied. Energy gap of about 10meV(116K) is observed along the one-dimensional, antiferromagnetic zone center, in good agreement with the magnetization measurement. The observed dispersion relation in the chain direction with the gap can be well described by the exact numerical results of S= 1, Heisenberg antiferromagnetic chain yielding an intrachain exchange of J/k_B=280± 10K.
社団法人日本物理学会の論文
1995-10-15