Thermal evolution of quasi-one-dimensional spin correlations within the anisotropic triangular lattice of .

Magnetic order on the spatially anisotropic triangular lattice of is studied via neutron diffraction measurements. The transition into a commensurate, collinear antiferromagnetic ground state with was found to occur below . Above this temperature, the transition is preceded by the formation of a coexisting, short-range ordered, incommensurate state below whose two-dimensional propagation vector evolves toward as the temperature approaches .

Amplitude mode in the planar triangular antiferromagnet NaMnO.

Amplitude modes arising from symmetry breaking in materials are of broad interest in condensed matter physics. These modes reflect an oscillation in the amplitude of a complex order parameter, yet are typically unstable and decay into oscillations of the order parameter's phase. This renders stable amplitude modes rare, and exotic effects in quantum antiferromagnets have historically provided a realm for their detection.

Reversible Flat to Rippling Phase Transition in Fe Containing Layered Battery Electrode Materials.

Layered sodium transition metal oxides of NaTMO (TM = 3d transition metal) show unique capability to mix different compositions of Fe to the TM layer, a phenomenon that does not exist in LiTMO. Here, a novel spontaneous TM layer rippling in the sodium ion battery cathode materials is reported, revealed by in situ X-ray diffraction, Cs-corrected scanning transmission electron microscopy, and density functional theory simulation, where the softening and distortion of FeO octahedra collectively drives the flat TM planes into rippled ones with inhomogeneous interlayer distance at high voltage. In such a rippling phase, charge and discharge of Na ions take different evolution pathways, resulting in an unusual hysteresis voltage loop.

Topological Magnon Bands in a Kagome Lattice Ferromagnet.

There is great interest in finding materials possessing quasiparticles with topological properties. Such materials may have novel excitations that exist on their boundaries which are protected against disorder. We report experimental evidence that magnons in an insulating kagome ferromagnet can have a topological band structure.

Thermal Hall Effect of Spin Excitations in a Kagome Magnet.

At low temperatures, the thermal conductivity of spin excitations in a magnetic insulator can exceed that of phonons. However, because they are charge neutral, the spin waves are not expected to display a thermal Hall effect. However, in the kagome lattice, theory predicts that the Berry curvature leads to a thermal Hall conductivity κ(xy).