Spin waves and revised crystal structure of honeycomb iridate Na2IrO3
(2012)
Spin waves and revised crystal structure of honeycomb iridate Na2IrO3
ArXiv 1202.1268 (2012)
Abstract:
We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zig-zag magnetic order. The onset of long-range magnetic order below 15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90 deg Ir-O-Ir bonds required for dominant Kitaev exchange.Helical scattering signatures of strain and electronic textures in YbFe 2 O 4 from three-dimensional reciprocal-space imaging
Physical Review B - Condensed Matter and Materials Physics 85:1 (2012)
Abstract:
The insulating ternary oxide YbFe 2O 4 displays an unusual frustration-driven incommensurate charge-ordering (CO) transition, linked to possible ferroelectricity. Based on high-resolution synchrotron data, we report a detailed structural model showing that the CO phase is an incommensurate charge-density wave and cannot be ferroelectric, since the electrical dipole moments are also incommensurately modulated. The change between continuous and "spotty" helices of scattering at the CO transition is attributed to three-dimensional fluctuations of the direction of the ordering wave vector. © 2012 American Physical Society.Electric field control of the magnetic chiralities in ferroaxial multiferroic RbFe(MoO4)2
arXiv [cond-mat.str-el] (2012) 1202.2317
Helical scattering signatures of strain and electronic textures in YbFe2O4 from three-dimensional reciprocal-space imaging
Phys. Rev. B 85 (2012) 014115