Behavior of magnetoelectric hysteresis and role of rare earth ions in multiferroicity in double perovskite Yb₂CoMnO₆

Double-perovskite multiferroics have been investigated because alternating orders of magnetic ions act as distinct magnetic origins for ferroelectricity. In Yb₂CoMnO₆, the frustrated antiferromagnetic order emerging at T_N = 52 K induces ferroelectric polarization perpendicular to the c axis through cooperative O²⁻ shifts via the symmetric exchange striction. In our detailed measurements of the magnetoelectric properties of single-crystalline Yb₂CoMnO₆, we observe full ferromagnetic-like hysteresis loops that are strongly coupled to the dielectric constant and ferroelectric polarization at various temperatures below T_N. Unlike Lu₂CoMnO₆ with non-magnetic Lu³⁺ ions, we suggest the emergence of additional ferroelectric polarization along the c axis below the ordering temperature of magnetic Yb³⁺ ions, T_Yb ≈ 20 K, based on the spin structure established from recent neutron diffraction experiments. While the proposed description for additional ferroelectricity, ascribed to the symmetric exchange striction between Yb³⁺ and Co²⁺/Mn⁴⁺ magnetic moments, is clearly given, anomalies of dielectric constants along the c axis are solely observed. Our interesting findings on magnetoelectric hysteresis and the possible development of additional ferroelectricity reveal notable characteristics of double perovskites and provide essential guidance for the further examination of magnetoelectric functional properties.