Magnetically driven electric polarization in frustrated magnetic oxide multiferroics

In multiferroics more than one ferroic order can coexist and in the present case we are interested in systems which exhibit simultaneous magnetic ordering and electric polarization (EP). Of particular interest are frustrated magnetic materials that exhibit an electric polarization that is strongly coupled to the magnetism [1]. Examples of such multiferroics are RMnO3 (R= Tb, Dy), Ni3V2O8, and RbFe(MoO4)2 [2-4]. This coupling can be utilized in applications such as magnetoelectric random access memory. Although technically relevant, the coupling mechanism between these two orders is complicated [1]. Whereas the magnetic ordering results from exchange interaction of unpaired spins, origins of EP coupled to the magnetic ordering depends on the interplay between lattice, orbital, spin and charge degrees of freedom. Several mechanisms such as the inverse Dzyaloshinskii-Moriya interaction, magnetostriction and coupling of the chirality to the crystal structure or a combination of them are currently discussed depending on the compound [2-5]. Additionally EP has ionic and electronic contributions. In the present work we investigate the coupling of magnetism to EP involving all three above mechanisms, in orthorhombic DyMnO3 (DMO), Cu3Nb2O8 and Ba3NiNb2O9 with neutron powder diffraction (NPD), magnetization and heat capacity measurements focusing on the magnetic and multiferroic phase transitions. In order to investigate the role of the lattice distortion or equivalently the role of oxygen, isotope substitution of 16O with 18O was performed on DMO. All samples are prepared as single phases via the solid state route and NPD experiments are carried out at Wombat and at Echidna at OPAL.
Polarization, Crystal structure, Coupling, Magnetic materials, Neutron diffraction, Spin, Interactions, Phase transformations
Narayanan, N., Reynolds, N., Li, F., Mulders, A. M., Rovillain, P., Ulrich, U., Bartkowiak, M., Hester, J., McIntyre, G., & Hutchinson, W. D. (2014). Magnetically driven electric polarization in frustrated magnetic oxide multiferroics. Paper presented at the 38th Annual Condensed Matter and Materials Meeting 2014, Waiheke Island Resort, Waiheke, Auckland, New Zealand 4th February - 7th February, 2014, (pp. 58-59). Retrieved from: