90,390 research outputs found
Large Magneto-Dielectric Effects in Orthorhombic HoMnO3 and YMnO3
We have found a remarkable increase (up to 60 %) of the dielectric constant
with the onset of magnetic order at 42 K in the metastable orthorhombic
structures of YMnO3 and HoMnO3 that proves the existence of a strong
magneto-dielectric coupling in the compounds. Magnetic, dielectric, and
thermodynamic properties show distinct anomalies at the onset of the
incommensurate magnetic order and thermal hysteresis effects are observed
around the lock-in transition temperature at which the incommensurate magnetic
order locks into a temperature independent wave vector. The orders of Mn3+
spins and Ho3+ moments both contribute to the magneto-dielectric coupling. A
large magneto-dielectric effect was observed in HoMnO3 at low temperature where
the dielectric constant can be tuned by an external magnetic field resulting in
a decrease of up to 8 % at 7 Tesla. By comparing data for YMnO3 and HoMnO3 the
contributions to the coupling between the dielectric response and Mn and Ho
magnetic orders are separated.Comment: revised manuscrip
Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSbTe
Substitution of Sb in FeSb by less than 0.5% of Te induces a transition
from a correlated semiconductor to an unconventional metal with large effective
charge carrier mass . Spanning the entire range of the semiconductor-metal
crossover, we observed an almost constant enhancement of the measured
thermopower compared to that estimated by the classical theory of electron
diffusion. Using the latter for a quantitative description one has to employ an
enhancement factor of 10-30. Our observations point to the importance of
electron-electron correlations in the thermal transport of FeSb, and
suggest a route to design thermoelectric materials for cryogenic applications.Comment: 3 pages, 3 figures, accepted for publication in Appl. Phys. Lett.
(2011
Microscopic Description of Band Structure at Very Extended Shapes in the A ~ 110 Mass Region
Recent experiments have confirmed the existence of rotational bands in the A
\~ 110 mass region with very extended shapes lying between super- and
hyper-deformation. Using the projected shell model, we make a first attempt to
describe quantitatively such a band structure in 108Cd. Excellent agreement is
achieved in the dynamic moment of inertia J(2) calculation. This allows us to
suggest the spin values for the energy levels, which are experimentally
unknown. It is found that at this large deformation, the sharply down-sloping
orbitals in the proton i_{13/2} subshell are responsible for the irregularity
in the experimental J(2), and the wave functions of the observed states have a
dominant component of two-quasiparticles from these orbitals. Measurement of
transition quadrupole moments and g-factors will test these findings, and thus
can provide a deeper understanding of the band structure at very extended
shapes.Comment: 4 pages, 3 eps figures, final version accepted by Phys. Rev. C as a
Rapid Communicatio
Melham's Conjecture on Odd Power Sums of Fibonacci Numbers
Ozeki and Prodinger showed that the odd power sum of the first several
consecutive Fibonacci numbers of even order is equal to a polynomial evaluated
at certain Fibonacci number of odd order. We prove that this polynomial and its
derivative both vanish at , and will be an integer polynomial after
multiplying it by a product of the first consecutive Lucas numbers of odd
order. This presents an affirmative answer to a conjecture of Melham.Comment: 15page
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