The "lone" 6s electron pair often plays a key role in determining the structure and physical properties of compounds containing sixth-row elements in their lower oxidation states: Tl(+), Pb(2+), and Bi(3+) with the [Xe]4f(14)5d(10)6s(2) electronic configuration. The lone pairs on these ions are associated with reduced structural symmetries, including ferroelectric instabilities and other important phenomena. Here we consider the isoelectronic auride Au(-) ion with the [Xe]4f(14)5d(10)6s(2) electronic configuration. Ab initio density functional theory methods are employed to probe the effect of the 6s lone pair in alkali-metal aurides (KAu, RbAu, and CsAu) with the CsCl structure. The dielectric constants, Born effective charges, and structural instabilities suggest that the 6s lone pair on the Au(-) anion is stereochemically inert to minor mechanical and electrical perturbation. Pressures greater than 14 GPa, however, lead to reorganization of the electronic structure of CsAu and activate lone-pair involvement and Au-Au interactions in bonding, resulting in a transformation from the cubic CsCl structure type to an orthorhombic Cmcm structure featuring zigzag Au-Au chains.

CoSeO(4) has a structure consisting of edge-sharing chains of Co(2+) octahedra which are held together by SeO(4)(2-) tetrahedra via shared oxygen atoms at the edges of the octahedra. DC magnetization measurements indicate a transition to an ordered state below 30 K. Powder neutron diffraction refinements suggest an ordered state with two unique antiferromagnetic chains within the unit cell. Isothermal magnetization measurements indicate a temperature-dependent field-induced magnetic transition below the ordering temperature. From neutron diffraction, we find that this corresponds to a realignment of spins from the canted configuration towards the c-axis. The dielectric constant shows a change in slope at the magnetic ordering temperature indicating an interplay between the spin and charge degrees of freedom.

We manipulate the magnetic states of ferromagnetic nanorings with an azimuthal Oersted field directed along the ring circumference. The circular field is generated by passing current through an atomic force microscope tip positioned at the center of the ring, and can directly control the chirality of the vortex state. We demonstrate switching from an onion state to a vortex state and between two vortex states, using magnetic force microscopy to image the resulting magnetic states. The understanding of the magnetization switching behavior in an azimuthal Oersted field could improve practical magnetic data storage devices.

Micromagnetic simulations of the vortex switching process of thin ferromagnetic rings under the application of a circular field, as if created from a current-carrying wire passing through the ring center, reveal that for rings with sub-micron dimensions and thicknesses on the order of the exchange length, the vortex to vortex switching process occurs through the nucleation and annihilation of multiple 360° domain walls (DWs). The DWs can be characterized by their circulation relative to the vortex circulation; the DWs form in pairs with opposite topological indices. The DW with the same circulation annihilates first, which has a smaller energy barrier to overcome before annihilating. The contributions from both the exchange energy and demagnetization energy must be considered to predict which DW will annihilate first. Either wall could be annihilated by offsetting the current toward the wall being targeted.

NEWS & ANALYSIS MATERIALS NEWSvoltage required to initiate thermal actuation and the curvature achievable for a given power input. Furthermore, increasing the number of TR proteins in the molecular composite extended the range of actuator deformation.