Multiboson spin-wave theory for Ba2CoGe2O7, a spin-3/2 easy-plane Neel antiferromagnet with strong single-ion anisotropy

Abstract

We consider the square-lattice antiferromagnetic Heisenberg Hamiltonian extended with a single-ion axial anisotropy term as a minimal model for the multiferroic Ba2CoGe2O7. Developing a multiboson spin-wave theory, we investigate the dispersion of the spin excitations in this spin-3/2 system. As a consequence of a strong single-ion anisotropy, a stretching (longitudinal) spin-mode appears in the spectrum. The inelastic neutron scattering spectra of Zheludev et al. [Phys. Rev. B 68, 024428 (2003)] are successfully reproduced by the low energy modes in the multiboson spin-wave theory, and we anticipate the appearance of the spin stretching modes at 4meV that can be identified using the calculated dynamical spin structure factors. We expect the appearance of spin stretching modes for any S>1/2 compound where the single-ion anisotropy is significant.

11 pages, 5 figures, references added, minor modifications in the text

References in corpus (6)

• Anomalous High-Energy Spin Excitations in La2CuO4
• Spin-stretching modes in anisotropic magnets: spin-wave excitations in the multiferroic Ba2CoGe2O7
• Magnetic order and dynamics of the charge-ordered antiferromagnet La1.5Sr0.5CoO4
• Gigantic magnetoelectric effect caused by magnetic-field-induced canted antiferromagnetic-paramagnetic transition in quasi-two-dimensional Ca${}_2$CoSi${}_2$O${}_7$ crystal
• Magnetic spectrum of the two-dimensional antiferromagnet La2CoO4 studied by inelastic neutron scattering
• Magnetic field-induced one-magnon Raman scattering in the magnon Bose-Einstein condensation phase of TlCuCl${}_3$