Subpicometer-scale atomic displacements and magnetic properties in the oxygen-isotope substituted multiferroic DyMn O3

We have investigated DyMn16O3 and its isotopically substituted counterpart DyMn18O3 by neutron powder diffraction, x-ray diffraction, and heat capacity measurements to investigate the mechanism leading to its magnetically induced electric polarization. 18O isotope substitution does not influence the magnetic ordering temperature of the Mn ions TN,Mn or the multiferroic ordering temperature Tl coinciding with the onset of the spin spiral phase; however, it does reduce the ordering temperature of Dy into its incommensurate magnetic state TN,Dy from 7.0(1) K to 5.9(1) K. The temperature dependence of the magnetic propagation vector, qIC, changes with 18O substitution, while Tl remains almost constant, independent of qIC. Pronounced changes in the lattice parameters occur at the various phase transitions. Furthermore, distinct subpicometer-scale distortions of the MnO6 octahedra and displacements of the Dy ions are observed below the ferroelectric phase transition at Tl in both samples, pointing toward the mechanism for electric polarization and its coupling to the orbital degrees of freedom. ©2017 American Physical Society

Keywords

Neutron diffraction, X-ray diffraction, Specific heat, Ferroelectric materials, Spin, Temperature dependence, Phase transformations

Citation

Narayanan, N., Graham, P. J., Reynolds, N., Li, F., Rovillain, P., Hester, J., Kimpton, J., Yethiraj, M., McIntyre, G. J., Hutchison, W. D., & Ulrich, C. (2017). Subpicometer-scale atomic displacements and magnetic properties in the oxygen-isotope substituted multiferroic DyMn O3. Physical Review B, 95(7), 075154. doi:10.1103/PhysRevB.95.075154