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A series of manganites Tb1− xHo xMnO3 (0≤ x≤0.6) with orthorhombic structure are synthesized and detailed investigations on their multiferroicity are performed. Successive magnetic transitions upon temperature variation are evidenced for all the samples, and both the Mn3+spiral spin ordering and rare-earth spin ordering are suppressed with increasing x. A significant enhancement of both the polarization and magnetoelectric response within 0.2< x<0.4 is observed, which may probably result from the shortening of the spiral-spin-ordering period, due to the competition between the spiral spin order and E-type antiferromagnetic order. This argument is supported by further theoretical calculations based on the two e g-orbital double-exchange model. [ABSTRACT FROM AUTHOR]

The terahertz dielectric response of LuFe2O4 is investigated by terahertz time-domain spectroscopy over a temperature range of 6–290 K. It is revealed that besides the central mode associated with the charge-ordered state, a soft TO1 mode at below ∼240 K is identified indicating the existence of displacing ferroelectricity, in addition to the charge-ordering-induced ferroelectricity at below 320 K. The anomaly of the soft mode at ∼180 K reflects the magnetoelectric correlation between the soft TO1 mode and the spin/charge fluctuations revealed recently. Finally, the magnetic property at below ∼240 K is discussed. [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]