Magnetic anisotropy and low-energy spin waves in the Dzyaloshinskii-Moriyaspiral magnet Ba2CuGe2O7

Neutron-diffraction and inelastic-scattering experiments are used to invest igate in detail the field dependence of the magnetic structure and low-ener gy spin-wave spectrum of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O7. T he results suggest that the previously proposed model for the magnetism of this compound (an ideal sinusoidal spin spiral, stabilized by isotropic exc hange and Dzyaloshinskii-Moriya interactions) needs to be refined. Both rec ent and previously published data can be quantitatively explained by taking into account the Kaplan-Shekhtman-Entin-Wohlman-Aharony term, a special ma gnetic anisotropy term that was predicted to always accompany Dzyaloshinski i-Moriya interactions in insulators. [S0163-1829(99)01017-6].