8 research outputs found
Detection of nano scale thin films with polarized neutron reflectometry at the presence of smooth and rough interfaces
By knowing the phase and modules of the reflection coefficient in neutron
reflectometry problems, a unique result for the scattering length density (SLD)
of a thin film can be determined which will lead to the exact determination of
type and thickness of the film. In the past decade, several methods have been
worked out to resolve the phase problem such as dwell time method, reference
layer method and variation of surroundings, among which the reference method
and variation of surroundings by using a magnetic substrate and polarized
neutrons is of the most applicability. All of these methods are based on the
solution of Schrodinger equation for a discontinuous and step-like potential at
each interface. As in real sample there are some smearing and roughness at
boundaries, consideration of smoothness and roughness of interfaces would
affect the final output result. In this paper, we have investigated the effects
of smoothness of interfaces on determination of the phase of reflection as well
as the retrieval process of the SLD, by using a smooth varying function (Eckart
potential). The effects of roughness of interfaces on the same parameters, have
also been investigated by random variation of the interface around it mean
position
The effects of ion-neutral collision frequency on the plasma sheath dynamics for oblique entrance of ions into the sheath
Recently it has been shown that the magnetic field has significant effects on the
characteristics of ions which enter the collisionless plasma sheath with an oblique
incidence angle. Here, we have investigated these effects in collisional plasma sheath.
Considering the ion-neutral collision, the basic equations of fluid model in a plasma
sheath have been numerically solved in the presence of an external magnetic field where
the ion collision frequency has a power law dependency to the ion flow velocity. The
results show that the effects of magnetic field on the plasma sheath dynamics strongly
depend on the ion-neutral collision frequency and its dependency to ion flow velocity
The effects of ion-neutral collision frequency on the plasma sheath dynamics for oblique entrance of ions into the sheath
Retrieval of the complex reflection coefficient from nano scale thin films by using polarized neutrons and magnetic substrates
Spin-polarized electron transfer in multilayers with different types of rough interfaces
In this study, the influence of interfacial roughness of multilayers structures on spin filter tunneling is investigated at low biases as a function of interfacial roughness type. The results show that the roughness causes the reduction of resonant tunneling, maximum achievable tunneling magneto resistance (TMR), and spin-filtering efficiency of tunneling structures. Based on the numerical results, decreasing the electronic devices’ efficiency is straight related to roughening of interfacial. Additionally, the effect of different temperatures is investigated on the spin polarization (SP). The values of SP decreased sensibly by increasing the temperature.https://www.springer.com/journal/109482021-01-02hj2020Mechanical and Aeronautical Engineerin
The sheath criterion for a collisional plasma sheath at the presence of external magnetic field
The Bohm sheath criterion is modified for collisional plasma containing
Boltzmann electrons and cold fluid ions at the presence of external magnetic
field. Based on fluid model, the effects of the strength and the orientation
of an external magnetic field on the upper and lower limits of Bohm sheath
criterion have been studied by considering the collision frequency between
ions and neutrals. The results show that the sheath criterion depends on the
orientation and magnitude of magnetic field and the ion flow velocity at the
sheath boundary