Multiferroicity and phase transitions in Tm-substituted GdMnO3

The multiferroic behaviors of polycrystalline Gd1-xTmxMnO3 are investigated by measuring the structural, magnetic, dielectric, and ferroelectric properties. Remarkable polarization is observed by partial Tm-substitution of Gd ions, and can be proposed to arise from the contribution of both the symmetric exchange striction (SS term) and asymmetric exchange striction (S x S term) in the ab-plane cycloidal structure at low substitution level. With further substitution, the polarization is gradually reduced, and it is suggested that the ferroelectric phase evolves from the ab-plane cycloidal structure to the bc-plane cycloidal structure where only the antisymmetric exchange striction (S x S term) contributes to the polarization. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745885]