The Magentic Susceptibility in Ultrathin Films of Magnetic Materials

1997 ◽  
Vol 494 ◽  
Author(s):  
Kamakhya P. Ghatak ◽  
P. K. Bose ◽  
Gautam Majumder
Keyword(s):  
Theoretical Analysis ◽  
Film Thickness ◽  
Magnetic Materials ◽  
Ultrathin Films ◽  
Critical Region ◽  
Diamagnetic Susceptibility ◽  
Numerical Computations ◽  
Dispersion Law

ABSTRACTIn this paper we have studied the dia and paramagentic susceptibilities of the holes in ultrathin films of magnetic materials in the presence of a parallel magentic field on the basis of a newly derived dispersion law for such systems. The numerical computations are performed taking Hg1-xMnx Te and Cd1-xMnx Se as examples. Both the susceptibilities increses with decreasing doping and film thickness respectively. It is important to note that not only the paramagnetic-to-diamagnetic susceptibility ratio for the present case deviates from (1/3) in conventional semiconductors, but also that is a critical region, where quenching of the diamagnetic occurs. The theoretical analysis is in agreement with the experimental datas as given elsewhere.

The Influence of Quantizing Magnetic Field on The Magnetic Susceptibilities in Ultra Thin Films of Dilute Magnetic Materials

1993 ◽  
Vol 313 ◽  
Author(s):  
Kamakhya P Ghatak ◽  
S. N. Biswas
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Thin Films ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Magnetic Materials ◽  
Ultrathin Films ◽  
Surface Concentration ◽  
Magnetic Susceptibilities ◽  
Quantizing Magnetic Field

ABSTRACTIn this paper we have studied the dia and paramagnetic susceptibilities of the holes in ultrathin films of dilute magnetic materials in the presence of a quantizing magnetic field and compared the same with that of the bulk specimens under magnetic quantization for the purpose of relative comparison. It is found, taking Hg1−xMnxTe and Cd1−xMnxSe as examples, that both the susceptibilities increase with decreasing film thickness and increasing surface concentration in oscillatory Manners. The numerical values of the susceptibilities in ultrathin films of dilute magnetic materials are greater than that of the bulk and the theoretical analysis is in agreement with the experimental data as reported elsewhere.

Change of sign in the Casimir interaction of peptide films deposited on a dielectric substrate

2020 ◽  
Vol 35 (03) ◽  
pp. 2040020 ◽  
Author(s):  
E. N. Velichko ◽  
M. A. Baranov ◽  
V. M. Mostepanenko
Keyword(s):  
Free Energy ◽  
Film Thickness ◽  
Silica Glass ◽  
Room Temperature ◽  
Glass Plate ◽  
Pressure Change ◽  
Dielectric Substrate ◽  
Numerical Computations ◽  
Peptide Coatings

The Casimir free energy and pressure of thin peptide films deposited on a dielectric substrate are investigated in the region of parameters where they change their sign. Numerical computations are performed for a modelled peptide film on a silica glass plate. The Casimir free energy is computed at room temperature as a function of the film thickness and the fraction of water contained in the film. It is shown that the values of the Casimir pressure change from negative to positive when the film thickness decreases to below some value in the region from 115 to 133 nm depending on the fraction of water in the film. Possible applications of the obtained results to the problem of stability of peptide coatings are discussed.

Report Paper 3: Elastohydrodynamic Lubrication of ‘O’ Ring Seals

1969 ◽  
Vol 184 (12) ◽  
pp. 197-200
Author(s):  
I. A. Gibson ◽  
C. J. Hooke ◽  
J. P. O'Donoghue
Keyword(s):  
Theoretical Analysis ◽  
Film Thickness ◽  
Pressure Gradient ◽  
Contact Zone ◽  
Elastohydrodynamic Lubrication ◽  
Iterative Solution ◽  
Contact Conditions ◽  
Dry Contact

This report gives details of a theoretical analysis of the lubrication of ‘O’ ring seals. Under dry contact conditions the pressure gradient at inlet to the contact zone is infinite, and an iterative solution has been developed to determine the inlet sweep of pressure under conditions of elastohydrodynamic lubrication. The exit film thickness and pressures have also been determined for conditions of variable outlet viscosity and pressure gradient. Typical results for an ‘O’ ring are given for a standard seal section.

Effect of Stress on the Carrier Contribution to Elastic Constants in Thin Films of Small Gap Compounds

1993 ◽  
Vol 308 ◽  
Author(s):  
Kamakhya P. Ghatak ◽  
Sambhu Nath Biswas
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Experimental Method ◽  
Elastic Constants ◽  
Electron Concentration ◽  
Ultrathin Films ◽  
Theoretical Formulation ◽  
Lattice Matched

ABSTRACTIn this paper we have investigated the carrier contribution to elastic constants in very thin films of stressed small gap compounds within the domain of theory. It is found, taking stressed ultrathin films Hg1-xCdxTe and In1-xGaxAsyP1-y lattice matched to InP as examples, that the elastic constants increase with increasing electron concentration and decreasing film thickness respectively in oscillatory manners. Besides the stress enhances the numerical values of such contribution to the elastic constants. In addition, the theoretical formulation is in agreement with the suggested experimental method of determining such constants in materials having arbitary dispersion laws.

Theoretical Analysis on Resistance-Temperature Characteristic of Ni/HCl-PANI Composites

2014 ◽  
Vol 852 ◽  
pp. 142-146 ◽  
Author(s):  
Sui Yu Qiu ◽  
Zhi Wei Yang ◽  
Hong Qiu
Keyword(s):  
Transition Temperature ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Temperature Characteristic ◽  
Substrate Thickness ◽  
Upper Limit ◽  
Metallic Conduction ◽  
Conduction Behavior ◽  
Doped Polyaniline ◽  
Semiconducting Behavior

Ni/HCl-PANI composites were formed by depositing Ni films on HCl-doped polyaniline (HCl-PANI) substrates. A simple parallel resistor model is used to analyze the resistance-temperature (R-T) characteristic of the composite within 30-300 K. The theoretical analysis reveals that the composite exhibits a metal-semiconductor transition within a certain thickness of the Ni film or the HCl-PANI substrate. The composite shows a semiconducting behavior at temperatures over the transition temperature and a metallic conduction behavior at temperatures below the transition temperature. The transition temperature increases with increasing Ni film thickness whereas it decreases with increasing HCl-PANI substrate thickness. When the Ni film thickness exceeds its upper limit or the HCl-PANI substrate thickness is below its lower limit, the composite only shows the metallic R-T characteristic. When the HCl-PANI substrate thickness exceeds its upper limit, the composite only exhibits the semicoducting R-T characteristic.

Computational analysis of the steady state performance of an adjustable/controllable multi-pad bearing profile under LBP orientations

2020 ◽  
pp. 095440622095770
Author(s):  
Girish Hariharan ◽  
Raghuvir Pai
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Computational Analysis ◽  
Fluid Film ◽  
Adjustable Mechanism ◽  
State Behaviour ◽  
Steady State Behaviour ◽  
Steady State Performance

A theoretical model of a four-pad bearing profile with unique adjustable or controllable features is simulated in the present study by considering load directed between the pads. Radial and tilt adjustable mechanism of the four bearing pads can effectively control and modify the rotor operating behaviour. Inward and outward motions of the bearing pads result in the generation of narrow and broader convergent regions, which directly influences the fluid film pressures. In the theoretical analysis, load-between-pad (LBP) orientations and pad adjustment configurations are taken account of by employing a modified film thickness equation. The effect of load position in influencing the steady state behaviour of the four-pad adjustable bearing under varied pad displaced conditions is analysed in this study. The outcome of the analysis highlighted the effectiveness of four-pad adjustable bearing in improving the steady state performance by operating under negative adjustment conditions and with load acting on the bearing pads.

Theoretical Analysis of Capacitive Effect of Roller Bearings on Repeated Starts and Stops of a Machine Operating Under the Influence of Shaft Voltages

1992 ◽  
Vol 114 (4) ◽  
pp. 818-822 ◽  
Author(s):  
Har Prashad
Keyword(s):  
Theoretical Analysis ◽  
Film Thickness ◽  
Power Supply ◽  
Charge Accumulation ◽  
Roller Bearings ◽  
Capacitive Effect ◽  
Time Required

A theoretical analysis has been carried out to study the capacitive effects of roller bearings on repeated starts and stops of a machine operating under the influence of shaft voltages. The analysis gives the time required for the charge accumulation and increase of charge with time on the bearing surfaces based on bearing capacitance, resistance of film thickness and the shaft voltage. Also, it investigates the effect of gradual leakage of the accumulated charges with time as the shaft voltage falls as soon as the power supply to the machine is switched off. This paper gives an approach to determine ratio of the number of shaft revolutions required for charge accumulation and gradual discharge of the accumulated charges on the bearing surfaces depending on bearing to shaft voltage. Also, number of repeated starts and stops before initiation of craters on roller track of races are established to restrict the deterioration and damage of bearings.

Fabrication of Multilayer Films Using a Spinning Process

2000 ◽  
Vol 648 ◽  
Author(s):  
Jinhan Cho ◽  
Kookheon Char ◽  
Jong-Dal Hong ◽  
Ki-Bong Lee
Keyword(s):  
Film Thickness ◽  
Thin Layer ◽  
Ultrathin Films ◽  
Multilayer Films ◽  
Cds Nanoparticles ◽  
Adsorption Time ◽  
X Ray ◽  
Spinning Process ◽  
Allylamine Hydrochloride ◽  
Spinning Speed

AbstractWe introduce a method to build up organic/organic and organic/inorganic multilayer films composed of cationic poly(allylamine hydrochloride) (PAH) and negatively charged poly(sodium 4-styrenesulfonate) (PSS) or inorganic cadmium sulfide (CdS) nanoparticles using a spinning process. Since the deposition of each layer is made at a high spinning speed, the adsorption time for the formation of a homogeneous thin layer takes only 8 to 15 seconds. The adsorbed film thickness per bilayer can be easily controlled from about 5Å to 40Å by varying the spinning speed (Ω) and the mole concentration of polyelectrolytes. We also demonstrated with X-ray reflectivity that the alternating organic/inorganic ultrathin films fabricated by the spin SA process retain highly ordered internal structure in comparison with those prepared by the conventional SA process.

scholarly journals A model system for foam fractionation

2013 ◽  
Vol 469 (2154) ◽  
pp. 20120727 ◽  
Author(s):  
S. Hutzler ◽  
S. T. Tobin ◽  
A. J. Meagher ◽  
A. Marguerite ◽  
D. Weaire
Keyword(s):  
Theoretical Analysis ◽  
Surfactant Solution ◽  
Model System ◽  
Foam Fractionation ◽  
Numerical Computations ◽  
Foam Drainage Equation ◽  
Theory And Experiment ◽  
Foam Drainage

A model system for theory and experiment that is relevant to foam fractionation consists of a column of foam moving through an inverted U-tube between two pools of surfactant solution. The foam drainage equation and its variants are used for a theoretical analysis of this process. In the limit in which the lengths of the two legs is large , exact analytic formulae may be derived for the key properties of the system. Numerical computations and experiments support these results.

Influence of Quantum Confinement on the Photoemission From Nonlinear Optical Materials

1997 ◽  
Vol 484 ◽  
Author(s):  
Amakhya P. Ghatak ◽  
P. K. Bose ◽  
Gautam Majumder
Keyword(s):  
Quantum Dots ◽  
Film Thickness ◽  
Quantum Confinement ◽  
Optical Materials ◽  
Nonlinear Optical ◽  
Nonlinear Optical Materials ◽  
Dispersion Law ◽  
Quantum Well Wires ◽  
Electron Dispersion ◽  
Theoretical Results

Abstractwells (QWs), quantum well wires (QWWs) and quantum dots (QDs) of nonlinear optical materials, respectively on the basis of a newly derived electron dispersion law considering all types of anisotropies within the framework of k.p. formalism. It is found, taking CdGeAs2, GaAs and InAs, as exmaples, that the photoemission increase with increasing photon energy in a ladder like manner and also exhibits oscillatory dependences with changing electron concentration with film thickness respectively for all types of quantum confinement. The photoemission current density is greatest in QDs and least in QWWs. In addition, the theoretical results are in agreement with the experimental observation as reported elsewhere.

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