Relationship between Magnetic Structure and Ferroelectricity of LiVCuO4

Abstract

Neutron scattering studies and measurements of the dielectric susceptibility ε and ferroelectric polarization P have been carried out under various magnetic fields H for single-crystal samples of the multiferroic system LiVCuO 4 with quasi one-dimensional spin 1/2 Cu 2+ chains formed of edge-sharing CuO 4 square planes, and the relationship between the magnetic structure and ferroelectricity has been studied. The ferroelectric polarization is significantly suppressed by the magnetic field H above 2 T applied along the a and b axes. When H = 0, a helical magnetic structure with the helical axis parallel to c has been confirmed. The magnetic structure under the field along a has been determined, where the a b -plane structure changes to the helical one with the helical axis parallel to H with increasing the field through ∼2 T. The ferroelectric polarization along a at H = 0 is found to be proportional to the neutron magnetic scattering intensity, indicating that the magnetic order is closely related to the appearance of the ferroelectricity. The relationship between the magnetic structure and ferroelectricity of LiVCuO 4 is discussed by considering the existing theories.