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The rare-earth double-perovskite R2CoMnO6 family has been reported to be promising multiferroics where the predicted ferroelectric polarization along the b-axis is induced by the Co2+/Mn4+ collinear magnetic order. In this work, we report our characterizations on the structural, magnetic, dielectric, and ferroelectric behaviors of flux-grown Y2CoMnO6 single crystals. A weak ferromagnetic transition with the Curie point TC ∼ 70 K is evident in combination with a remarkable magnetic hysteresis loop along the c-axis. The earlier reported dielectric anomaly at the magnetic transition is not detected in our single crystals. In addition, the peak of each electric current curve as a function of temperature, probed along different crystallographic directions, shows serious shifting with the temperature ramping rate, excluding the intrinsic ferroelectric contribution. The measured data are not in conformity with theoretical predictions and earlier experiments on polycrystalline samples. In addition, no reliable sign for magnetoelectric coupling can be detected. The present work seems to exclude the existence of magnetism-driven ferroelectricity in Y2CoMnO6. [ABSTRACT FROM AUTHOR]

Hybrid improper ferroelectrics have their electric polarization generated by two or more combined non-ferroelectric structural distortions, such as the rotation and tilting of Ti-O octahedral in the Ca3Ti2O7 (CTO) family. In this work, we prepare the high quality (010)-oriented CTO thin films on (110) SrTiO3 (STO) substrates by pulsed laser deposition. The good epitaxial growth of the CTO thin films on the substrates with the interfacial epitaxial relationship of [001]CTO//[001]STO and [100]CTO//[-110]STO is revealed. The in-plane ferroelectric hysteresis unveils an ultralow coercive field of ~5 kV/cm even at low temperature, nearly two orders of magnitude lower than that of bulk CTO single crystals. The huge difference between the epitaxial thin films and bulk crystals is most likely due to the lattice imperfections in the thin films rather than substrate induced lattice strains, suggesting high sensitivity of the ferroelectric properties to lattice defects. [ABSTRACT FROM AUTHOR]

The magnetization, Raman spectroscopy, and ferroelectricity of multiferroic GdMn2O5 as a function of temperature and magnetic field are investigated. The complicated magnetic transitions at low temperatures are featured with anomalous Raman mode shifts, dielectric response, and ferroelectricity generation, indicating the significant spin–phonon coupling. It is argued that this coupling is possibly responsible for the electrical polarization generation associated with the incommensurate–commensurate transition. [ABSTRACT FROM AUTHOR]

The magnetization, Raman spectroscopy, and ferroelectricity of multiferroic GdMn2O5 as a function of temperature and magnetic field are investigated. The complicated magnetic transitions at low temperatures are featured with anomalous Raman mode shifts, dielectric response, and ferroelectricity generation, indicating the significant spin–phonon coupling. It is argued that this coupling is possibly responsible for the electrical polarization generation associated with the incommensurate–commensurate transition. [ABSTRACT FROM AUTHOR]