V-2 spin dynamics in low dimensional antiferromagnets. Spin-nematic interaction in square-lattice antiferromagnet Ba₂CoGe₂O₇

The enhanced simultaneous order in magnetism and dielectricity, multiferroics, has been extensively studied since the discovery of its experimental realization in the perovskite manganite TbMnO₃. Among the multiferroic materials Ba₂CoGe₂O₇ is a rare experimental realization where the electric polarization is represented by spin-nematic operators. We revealed the existence of spin-nematic interaction by combination of magnetization and neutron scattering experiments and we determined the dielectric energy by analyzing neutron scattering spectrum. We propose that the spin-nematic interaction constant can be a performance index of multiferroic device. (author)