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

Double-perovskite multiferroics have been investigated because alternating orders of magnetic ions act as distinct magnetic origins for ferroelectricity. In YbCoMnO, the frustrated antiferromagnetic order emerging at T = 52 K induces ferroelectric polarization perpendicular to the c axis through cooperative O shifts via the symmetric exchange striction. In our detailed measurements of the magnetoelectric properties of single-crystalline YbCoMnO, we observe full ferromagnetic-like hysteresis loops that are strongly coupled to the dielectric constant and ferroelectric polarization at various temperatures below T. Unlike LuCoMnO with non-magnetic Lu ions, we suggest the emergence of additional ferroelectric polarization along the c axis below the ordering temperature of magnetic Yb ions, T ≈ 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 Yb and Co/Mn 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.