Dzyaloshinskii-Moriya interaction and the magnetic ground state in magnetoelectric LiCoPO₄

Magnetic structures are investigated by means of neutron diffraction to shine a light on the intricate details that are believed to be key to understanding the magnetoelectric effect in LiCoPO₄. At zero field, a spontaneous spincanting of ϕ = 7(1)° is found. The spins tilt away from the easy b-axis toward c. Symmetry considerations lead to the magnetic point group m'_z, which is consistent with the previously observed magnetoelectric tensorform and weak ferromagnetic moment along b. For magnetic fields applied along a, the induced ferromagnetic moment couples via the Dzyaloshinskii-Moriya interaction to yield an additional field-induced spin canting. An upper limitto the size of the interaction is estimated from the canting angle.