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

Magnetic susceptibility, specific heat, dielectric, and electric polarization of LiCuFe2(VO4)(3) have been investigated. Two sequential antiferromagnetic transitions at T-N1 similar to 9.95 K and T-N2 similar to 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.