42 research outputs found
Ferromagnetic one dimensional Ti atomic chain
Using the full potential linearized augmented plane wave (FLAPW) method, we
have explored the magnetic properties of one dimensional (1D) Ti atomic chain.
Astonishingly, we for the first time observed that the 1D Ti atomic chain has
ferromagnetic ground state even on NiAl(110) surface although the Ti has no
magnetic moment in bulk or macroscopic state. It was found that the physical
property of direct exchange interaction among Ti atoms occurred in free
standing state is well preserved on NiAl(110) surface and this feature has an
essential role in ferromagnetism of 1D Ti atomic chain. It was shown that the
m= state has the largest contribution to the magnetic moment of Ti atom
grown on NiAl(110) surface. In addition, we found that the magnetic dipole
interaction is a key factor in the study of magnetic anisotropy, not the
magnetocrystalline anisotropy arising from spin-orbit interaction
Bias Voltage and Temperature Dependence of Hot Electron Magnetotransport
We present a qualitative model study of energy and temperature dependence of
hot electron magnetotransport. This model calculations are based on a simple
argument that the inelastic scattering strength of hot electrons is strongly
spin and energy dependent in the ferromagnets. Since there is no clear
experimental data to compare with this model calculations, we are not able to
extract clear physics from this model calculations. However, interestingly this
calculations display that the magnetocurrent increases with bias voltage
showing high magnetocurrent if spin dependent imaginary part of proper self
energy effect has a substantial contribution to the hot electron
magnetotransport. Along with that, the hot electron magnetotransport is
strongly influence by the hot electron spin polarization at finite
temperatures
Hot Electron Magnetotransport in a Spin-Valve Transistor at Finite temperatures
The hot electron magnetotransport in a spin-valve transistor has been
theoretically explored at finite temperatures. We have explored the parallel
and anti-parallel collector current changing the relative spin orientation of
the ferromagnetic layers at finite temperatures. In this model calculations,
hot electron energy redistribution due to spatial inhomogeneity of Schottky
barrier heights and hot electron spin polarization in the ferromagnetic layer
at finite temperatures have been taken into account. The results of this model
calculations accord with the experimental data semi-quantitative manner. We
therefore suggest that both effects remarked above should be taken into account
substantially when one explores the hot electron magnetotransport in a
spin-valve system transistor at finite temperatures.Comment: p pages, 3 figure
The Contribution of Hot Electron Spin Polarization to the Magnetotransport in a Spin-Valve Transistor at Finite Temperatures
The effect of spin mixing due to thermal spin waves and temperature
dependence of hot electron spin polarization to the collector current in a
spin-valve transistor has been theoretically explored. We calculate the
collector current as well as the temperature dependence of magnetocurrent at
finite temperatures to investigate the relative importance of spin mixing and
hot electron spin polarization. In this study the inelastic scattering events
in ferromagnetic layers have been taken into account to explore our interests.
The theoretical calculations suggest that the temperature dependence of hot
electron spin polarization has substantial contribution to the magnetotransport
in the spin-valve transistor.Comment: 8 pages and 6 figure
Localization lengths of ultrathin disordered gold and silver nanowires
The localization lengths of ultrathin disordered Au and Ag nanowires are
estimated by calculating the wire conductances as functions of wire lengths. We
study Ag and Au monoatomic linear chains, and thicker Ag wires with very small
cross sections. For the monoatomic chains we consider two types of disorder:
bounded random fluctuations of the interatomic distances, and the presence of
random substitutional impurities. The effect of impurity atoms on the nanowire
conductance is much stronger. Our results show that electrical transport in
ultrathin disordered wires may occur in the strong localization regime, and
with relatively small amounts of disorder the localization lengths may be
rather small. The localization length dependence on wire thickness is
investigated for Ag nanowires with different impurity concentrations.Comment: 6 pages, postscript figures included, submitted to PR
Graphene Induced High Thermoelectric Performance in ZnO/Graphene Heterostructure
Abstract Despite the low thermoelectric (TE) efficiency of graphene, its flexibility features are attractive for flexible and wearable next‐generation thermoelectric applications. So, it will be highly desirable to synthesize graphene‐based high TE material. Hence, the possibility of significant enhancement of the TE performance in ZnO/graphene heterostructure is investigated. The ZnO monolayer has a direct band gap of 3.3 eV, while a band gap of 5 meV in the ZnO/graphene heterostructure is found. The highest ZT ≈ 2.4 in the n‐doped ZnO/graphene heterostructure at 500 K is obtained, whereas the ZnO monolayer shows ZT ≈ 1.3 at 700 K. Particularly, this giant ZT in the ZnO/graphene heterostructure is found even at a low carrier concentration (≈1011 carrier cm−2). Besides, the ZnO/graphene heterostructure also displays a ZT ≈ 0.8 even at 300 K with a very low carrier concentration (≈1010 carrier cm−2). This outstanding TE performance originates from the TE coefficient advantages of each layer; high electrical conductivity from graphene and high Seebeck coefficient from ZnO incorporate with reduced thermal conductivity in the heterostructure. The findings will stimulate further studies to confirm the results as well as the development of flexible TE generators based on graphene for Internet of things thermoelectric applications