Dzyaloshinskii-Moriya interaction and the magnetic ground state in magnetoelectric LiCoPO\(_4\)

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 LiCoPO\(_4\) . At zero field, a spontaneous spin canting of \(\varphi = 7(1)^{\circ}\) 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 tensor form 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 limit to the size of the interaction is estimated from the canting angle.