Ferroelectricity of polycrystalline GdMnO3 and multifold magnetoelectric responses

The multiferroic behaviors of polycrystalline GdMnO3 are investigated by focusing on the ferroelectric response to the spin ordering sequence and external magnetic field. The polarization current shows sensitive response to both the Mn cycloidal spin order and Gd antiferromagnetic (AFM) order. The complicated magnetoelectric behaviors suggest that the Mn cycloidal spin order can be modulated by the Gd AFM order at low temperature via the Gd-Mn spin interaction. Due to the possible disorder and defects in polycrystalline nature, polycrystalline GdMnO3 may accommodate the cycloidal spin order in addition to the A-type AFM order at Mn sites, as illustrated by simulation based on the two-orbit double exchange model and measured hysteresis loops of polarization against magnetic field, indicating the switching of the ferroelectric domains coupled with the magnetic domains in response to magnetic field.