Browsing by Author "Argyriou, D"

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    Magnetoelectric coupling in isotopically substituted TbMn16/18O3 and RMn2O5 (R=Tb, Ho and Y) explored by Raman light spectroscopy
    (Australian Institute of Physics, 2014-02-04) Graham, PJ; Rovillian, P; Mulders, AM; Yethiraj, M; Argyriou, D; Pomjakushina, E; Condor, K; Kenzelmann, M; Ulrich, C
    Multiferroic materials demonstrate excellent potential for next-generation multifunctional devices, as they exhibit coexisting ferroelectric and magnetic orders. In magnetoelectric multiferroics, the existing coupling between both properties offers a unique possibility to manipulate ferroelectricity via magnetic order and vice versa opening unexpected new potential for high-density information storage and sensor applications. At present, the underlying physics of the magnetoelectric coupling is not fully understood, and competing theories propose conflicting experimental outcomes. By studying the lattice and magnetic excitations via Raman light scattering, we have obtained insight into the various coupling mechanism in multiferroic materials like TbMnO3 and RMn2O5 (R = Tb, Ho, and Y). Raman light scattering experiments were performed on TbMn16/18O3 oxygen-isotopesubstituted single crystals. Pronounced anomalies in sign and strength of the phonon shifts at the magnetic phase transition at 43 K and the ferroelectric phase transition at 28 K indicate an interaction between the lattice and the magnetic and electric ordering, providing information about the nature of the competing magnetic interactions present in this compound. Our Raman light scattering experiments on RMn2O5 (R = Tb, Ho, and Y) revealed opposite spin-phonon interactions for R = magnetic Tb and Ho, in contrast to non-magnetic Y. This offers a unique insight in the various competing spin exchange interactions, which lead to the highly frustrated spin structure and finally the multiferroic properties of RMn2O5. Using single crystal neutron diffraction at high magnetic fields (up to 11 T) we were able to determine a theoretically proposed but hitherto unobserved crystallographic phase transition, which naturally explains the origin of the ferroelectric polarization.