3,988 research outputs found
Structural Properties of Two-Dimensional Strontium Titanate: A First-Principles Investigation
Motivated by the experimental synthesis of two-dimensional (2D) perovskite
materials, we study the stability of 2D SrTiO from first principles. We
find that the TiO octahedral rotations emerge in 2D SrTiO with a
rotation angle twice that in the 3D bulk. The rotation angle decreases
significantly with the film thickness, reflecting the strong interlayer
coupling that is absent in the conventional 2D materials. Using the molecular
dynamics simulations, the cubic-like phase is found to appear above 1000 K that
is much higher than the transition temperature of 3D SrTiO.Comment: 5 pages, 4 figure
Magnetic field induced effects in the high source-drain bias current of weakly coupled vertical quantum dot molecules
We report on the basic properties of recently observed magnetic field
resonance, induced time dependent oscillation, and hysteresis effects in the
current flowing through two weakly coupled vertical quantum dots at high
source-drain bias (up to a few tens of mV). These effects bare some similarity
to those reported in the N=2 spin-blockade regime, usually for weak in-plane
magnetic field, of quantum dot molecules and attributed to hyperfine coupling,
except here the measurements are conducted outside of the spin-blockade regime
and the out-of-plane magnetic field is up to ~6 T.Comment: 3 pages, 3 figures, accepted for publication in Physica E in EP2DS 17
conference proceeding
Determination of effective microscopic models for the frustrated antiferromagnets CsCuCl and CsCuBr by density functional methods
We investigate the electronic and magnetic properties of the frustrated
triangular-lattice antiferromagnets CsCuCl and CsCuBr in the
framework of density functional theory. Analysis of the exchange couplings J
and J' using the available X-ray structural data corroborates the values
obtained from experimental results for CsCuBr but not for
CsCuCl. In order to understand this discrepancy, we perform a detailed
study of the effect of structural optimization on the exchange couplings of
CsCuCl employing different exchange-correlation functionals. We find
that the exchange couplings depend on rather subtle details of the structural
optimization and that only when the insulating state (mediated through spin
polarization) is present in the structural optimization, we do have good
agreement between the calculated and the experimentally determined exchange
couplings. Finally, we discuss the effect of interlayer couplings as well as
longer-ranged couplings in both systems.Comment: Phys. Rev. B in pres
Two level anti-crossings high up in the single-particle energy spectrum of a quantum dot
We study the evolution with magnetic field of the single-particle energy
levels high up in the energy spectrum of one dot as probed by the ground state
of the adjacent dot in a weakly coupled vertical quantum dot molecule. We find
that the observed spectrum is generally well accounted for by the calculated
spectrum for a two-dimensional elliptical parabolic confining potential, except
in several regions where two or more single-particle levels approach each
other. We focus on two two-level crossing regions which show unexpected
anti-crossing behavior and contrasting current dependences. Within a simple
coherent level mixing picture, we can model the current carried through the
coupled states of the probed dot provided the intrinsic variation with magnetic
field of the current through the states (as if they were uncoupled) is
accounted for by an appropriate interpolation scheme.Comment: 4 pages, 4 figures, accepted for publication in Physica E in MSS 13
conference proceeding
Spin-accumulation in small ferromagnetic double barrier junctions
The non-equilibrium spin accumulation in ferromagnetic double barrier
junctions is shown to govern the transport in small structures. Transport
properties of such systems are described by a generalization of the theory of
the Coulomb blockade. The spin accumulation enhances the magnetoresistance. The
transient non-linear transport properties are predicted to provide a unique
experimental evidence of the spin-accumulation in the form of a reversed
current on time scales of the order of the spin-flip relaxation time.Comment: 4 pages, 3 figures, to appear in PR
Resistive detection of the Néel temperature of Cr₂O₃ thin films
Although bulk magnetic properties of various antiferromagnets have been vigorously studied since long ago, their properties in the form of thin films, which are more relevant to antiferromagnetic spintronic devices, have not been investigated as much. In this work, we characterized the Néel temperature of Cr₂O₃ thin films by investigating the temperature dependence of the spin Hall magnetoresistance in Cr₂O₃/Pt bilayers. A precise determination of the Néel temperature was made possible by carefully designing the direction of the magnetic anisotropy in Cr₂O₃. The results provide a reliable way to determine the Néel temperature of antiferromagnetic thin films.Tatsuya Iino, Takahiro Moriyama, Hiroyuki Iwaki, Hikaru Aono, Yu Shiratsuchi, and Teruo Ono, Appl. Phys. Lett. 114, 022402 (2019); https://doi.org/10.1063/1.5082220
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