Room-Temperature Ferrimagnet with Frustrated Antiferroelectricity: Promising Candidate Toward Multiple State Memory

On the basis of first-principles calculations we show that the M-type hexaferrite BaFe12O19 exhibits frustrated antiferroelectricity associated with its trigonal bipyramidal Fe3+ sites. The ferroelectric (FE) state of BaFe12O19, reachable by applying an external electric field to the antiferroelectric (AFE) state, can be made stable at room temperature by appropriate element substitution or strain engineering. Thus M-type hexaferrite, as a new type of multiferoic with coexistence of antiferroelectricity and ferrimagnetism, provide a basis for studying the phenomenon of frustrated antiferroelectricity and realizing multiple state memory devices.Comment: supporting material available via email. arXiv admin note: text overlap with arXiv:1210.7116 by other author

Low Temperature Superfluid Response of High-Tc Superconductors

We have reviewed our theoretical and experimental results of the low temperature superfluid response function of high temperature superconductors (HTSC). In clean high-Tc materials the in-plane superfluid density rho_s^{ab} varies linearly with temperature. The slope of this linear T term is found to scale approximately with 1/Tc which, according to the weak coupling BCS theory for a d-wave superconductor, implies that the gap amplitude scales approximately with Tc. A T^5 behavior of the out-of-plane superfluid density rho_s^c for clean tetragonal HTSC was predicted and observed experimentally in the single layer Hg-compound HgBa_2CuO_{4+delta}. In other tetragonal high-Tc compounds with relatively high anisotropy, such as Hg_2Ba_2Ca_2Cu_3O_{8+delta}, rho_s^c varies as T^2 due to disorder effects. In optimally doped YBa_2Cu_3O_{7-delta}, rho_s^c varies linearly with temperature at low temperatures, but in underdoped YBa_2Cu_3O_{7-delta}, rho_s^c varies as T^2 at low temperatures; these results are consistent with our theoretical calculations.Comment: 26 pages, 8 figure

Relational Structure of Measurement with Application on Specification of Freeform Surface

A contradiction is shown in this paper that, for contact surface measurement, if a measured surface profile is exactly coincident with the USL (upper specification limit), the measured result may still be out of specification. To understand and avoid this contradiction, a relational construction of measurement is proposed bases on the representational measurement theory. By observing the connection between measurement and inverse problem, measurement is modeled as a mapping from the preordered set of measurands (objects to be measured) to the partially ordered set of measured values. Thereby, a desired property of the specifications limits is derived, and a correction of the USL of surface profile is proposed

Evolution of a disc-planet system with a binary companion on an inclined orbit

We study orbital inclination changes associated with the precession of a disc-planet system that occurs through gravitational interaction with a binary companion on an inclined orbit. We investigate whether this scenario can account for giant planets on close orbits highly inclined to the stellar equatorial plane. We obtain conditions for maintaining approximate coplanarity and test them with SPH-simulations. For parameters of interest, the system undergoes approximate rigid body precession with modest warping while the planets migrate inwards. Because of pressure forces, disc self-gravity is not needed to maintain the configuration. We consider a disc and single planet for different initial inclinations of the binary orbit to the midplane of the combined system and a system of three planets for which migration leads to dynamical instability that reorders the planets. As the interaction is dominated by the time averaged quadrupole component of the binary's perturbing potential, results for a circular orbit can be scaled to apply to eccentric orbits. The system responded adiabatically when changes to binary orbital parameters occurred on time scales exceeding the orbital period. Accordingly inclination changes are maintained under its slow removal. Thus the scenario for generating high inclination planetary orbits studied here, is promising.Comment: 16 pages, 13 figures, accepted for publication by MNRA

Disorder effect in low dimensional superconductors

The quasiparticle density of states (DOS), the energy gap, the superfluid density $\rho_s$, and the localization effect in the s- and d-wave superconductors with non-magnetic impurity in two dimensions (2D) are studied numerically. For strong (unitary) scatters, we find that it is the range of the scattering potential rather than the symmetry of the superconducting pairing which is more important in explaining the impurity dependences of the specific heat and the superconducting transition temperature in Zn doped YBCO. The localization length is longer in the d-wave superconducting state than in the normal state, even in the vicinity of the Fermi energy.Comment: 2 pages, uuencoded compressed postscript file, IRC-940610