Direct Evidence for an Intermediate Multiferroic Phase in LiCuFe₂(VO₄)₃

Abstract

Magnetic susceptibility, specific heat, dielectric, and electric polarization of LiCuFe2(VO4)3 have been investigated. Two sequential antiferromagnetic transitions at T N1 ∼ 9.95 K and T N2 ∼ 8.17 K are observed under zero magnetic field. Although a dielectric peak at T N1 is clearly identified, the measured pyroelectric current also exhibits a sharp peak at T N1, implying the magnetically relevant ferroelectricity. Interestingly, another pyroelectric peak around T N2 with an opposite signal is observed, resulting in the disappearance of electric polarization below T N2. Besides, the electric polarization is significantly suppressed in response to external magnetic field, evidencing a remarkable magnetoelectric effect. These results suggest the essential relevance of the magnetic structure with the ferroelectricity in LiCuFe2(VO4)3, deserving further investigation of the underlying mechanism.