Direct Evidence for an Intermediate Multiferroic Phase in LiCuFe 2 (VO 4 ) 3 .

Magnetic susceptibility, specific heat, dielectric, and electric polarization of LiCuFe 2 (VO 4 ) 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 LiCuFe 2 (VO 4 ) 3 , deserving further investigation of the underlying mechanism.