scholarly journals Tricriticality of the Blume–Emery–Griffiths model in thin films of stacked triangular lattices

2016 ◽  
Vol 30 (07) ◽  
pp. 1650071
Author(s):  
Sahbi El Hog ◽  
H. T. Diep
Keyword(s):  
Exchange Interaction ◽  
Low Temperatures ◽  
Lattice Site ◽  
Film Surface ◽  
Critical Value ◽  
Layer By Layer ◽  
Superfluid Phase ◽  
First Order ◽  
Interior Layers ◽  
Triangular Lattices

We study in this paper the Blume–Emery–Griffiths model in a thin film of stacked triangular lattices. The model is described by three parameters: bilinear exchange interaction between spins [Formula: see text], quadratic exchange interaction [Formula: see text] and single-ion anisotropy [Formula: see text]. The spin [Formula: see text] at the lattice site [Formula: see text] takes three values [Formula: see text]. This model can describe the mixing phase of He-4 [Formula: see text] and He-3 [Formula: see text] at low temperatures. Using Monte Carlo simulations, we show that there exists a critical value of [Formula: see text] below (above) which the transition is of second-(first-)order. In general, the temperature dependence of the concentrations of He-3 is different from layer by layer. At a finite temperature in the superfluid phase, the film surface shows a deficit of He-4 with respect to interior layers. However, effects of surface interaction parameters can reverse this situation. Effects of the film thickness on physical properties will be also shown as functions of temperature.

scholarly journals A theoretical study of a possible model of paramagnetic alums at low temperatures

1940 ◽  
Vol 176 (965) ◽  
pp. 203-213 ◽  
Keyword(s):  
Magnetic Field ◽  
Low Temperatures ◽  
Theoretical Study ◽  
Spontaneous Magnetization ◽  
Critical Value ◽  
Transition Curve ◽  
Thin Specimen ◽  
First Order ◽  
Freely Suspended ◽  
Line Of Critical Points

An attempt is made to examine theoretically the properties of paramagnetic alums at low temperatures. The model taken is a lattice of freely suspended magnets, all interactions except purely magnetic being neglected. Even with this simplification it is impossible at present to make rigorous calculations of the partition function, either on classical or quantum lines. A simple model is proposed, which is really a generalization of the Bragg - Williams theory enabling one to take account of the effect of a magnetic field. The few configurations whose energies are known are used to fix arbitrary constants in the expression assumed for the energy. The theory predicts that the state of lowest energy is either a spontaneously magnetized, state for a long thin specimen, or a state in which alternate rows of magnets point in opposite directions for a sphere, spontaneous magnetization appearing in an ellipsoid with an eccentricity greater than a certain critical value. The transition curve bounding the region in which the antiparallel state is stable consists partly of a line of Curie points corresponding to transitions of the second, order, passing smoothly into a line of critical points corresponding to a transition of the first order. The effect of shape on the magnetic properties of the specimen seems to be experimentally verified, but the rough nature of the theory prevents it being more than qualitative.

Epitaxial growth manner and structure of superconducting oxide films

1990 ◽  
Vol 48 (4) ◽  
pp. 2-3
Author(s):  
Yoshichika Bando ◽  
Takahito Terashima ◽  
Kenji Iijima ◽  
Kazunuki Yamamoto ◽  
Kazuto Hirata ◽  
...  
Keyword(s):  
Ultrathin Films ◽  
Film Surface ◽  
High Energy ◽  
Epitaxial Films ◽  
Layer By Layer ◽  
Initial Growth ◽  
In Situ Growth ◽  
High Quality ◽  
Activated Reactive Evaporation

The high quality thin films of high-Tc superconducting oxide are necessary for elucidating the superconducting mechanism and for device application. The recent trend in the preparation of high-Tc films has been toward “in-situ” growth of the superconducting phase at relatively low temperatures. The purpose of “in-situ” growth is to attain surface smoothness suitable for fabricating film devices but also to obtain high quality film. We present the investigation on the initial growth manner of YBCO by in-situ reflective high energy electron diffraction (RHEED) technique and on the structural and superconducting properties of the resulting ultrathin films below 100Å. The epitaxial films have been grown on (100) plane of MgO and SrTiO, heated below 650°C by activated reactive evaporation. The in-situ RHEED observation and the intensity measurement was carried out during deposition of YBCO on the substrate at 650°C. The deposition rate was 0.8Å/s. Fig. 1 shows the RHEED patterns at every stage of deposition of YBCO on MgO(100). All the patterns exhibit the sharp streaks, indicating that the film surface is atomically smooth and the growth manner is layer-by-layer.

Laser-Induced Pretransitional Ordering And Nonlinear Optical Properties Of Rigid-Rod Polymer Suspensions

1993 ◽  
Vol 328 ◽  
Author(s):  
Boris E. Vugmeister ◽  
Michelle S. Malcuit ◽  
John C. Kralik ◽  
Colleen Stevens
Keyword(s):  
Phase Transition ◽  
Colloidal Particles ◽  
Volume Fraction ◽  
Orientational Order ◽  
Critical Value ◽  
Orientational Relaxation ◽  
First Order ◽  
First Order Phase Transition ◽  
Rigid Rod ◽  
First Order Phase

ABSTRACTWe investigate the pretransitional behavior in laser-induced alignment of rigid rod-like polytetraflouroethylene (PTFE) suspensions. Using a laser-induced birefringence experiment, we measure both the orientational order parameter and the orientational relaxation time. We find that both increase as the volume fraction of colloidal particles approaches the critical value for the isotropic-nematic phase transition. Experimental results are compared with theory which takes into account the possibility of a first-order phase transition induced by a laser electric field.

Self-assembly layer-by-layer fabrication using porphyrin dye anion and polycation

2009 ◽  
Vol 13 (07) ◽  
pp. 774-778 ◽  
Author(s):  
Byung-Soon Kim ◽  
Young-A Son
Keyword(s):  
Ultrathin Films ◽  
Self Assembly ◽  
Film Surface ◽  
Layer By Layer ◽  
Preparation Technique ◽  
Force Microscopy ◽  
Atomic Force ◽  
Diallyldimethylammonium Chloride ◽  
Afm Analysis ◽  
Progressive Growth

In this study, self-assembled alternating film using poly(diallyldimethylammonium chloride) (PDDAC) and meso-tetrakis(4-carboxyphenyl)porphyrin (MTCP) was prepared as a multilayer deposition on glass substrate. This preparation technique for dye deposition may provide new feasibilities to achieve the manufacture of ultrathin films for nanotechnology application. The deposition films were characterized by UV-vis spectrophotometer and Atomic Force Microscopy (AFM) analysis. The results of UV-vis spectra showed that the absorbance characteristic of the multilayer films linearly increased with an increased number of PDDAC and MTCP bilayers. AFM analysis showed the film surface was relatively uniform and the progressive growth of layers was determined.

scholarly journals ANALYTIC STUDY OF FIRST-ORDER PHASE TRANSITION IN HOLOGRAPHIC SUPERCONDUCTOR AND SUPERFLUID

2013 ◽  
Vol 28 (28) ◽  
pp. 1350140 ◽  
Author(s):  
WUNG-HONG HUANG
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Critical Value ◽  
Analytic Study ◽  
Matching Method ◽  
Holographic Superconductor ◽  
First Order ◽  
Numerical Result ◽  
First Order Phase Transition ◽  
First Order Phase

We use the matching method to investigate the first-order phase transition in holographic superconductor and superfluid. We first use the simple holographic superconductor model to describe the matching method and mention how to see the first-order phase transition. Next, we study the holographic superconductor with Stückelberg term and see that the analytic results indicate the existence of first-order phase transition. Finally, we study the holographic superfluid and show that the first-order phase transition can be found for some values of parameters. We determine the critical value analytically and compare it with the previous numerical result.

THE THERMAL DECOMPOSITION OF HYDROGEN PEROXIDE VAPOUR. II.

1947 ◽  
Vol 25b (2) ◽  
pp. 135-150 ◽  
Author(s):  
Paul A. Giguère
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Thermal Decomposition ◽  
Low Temperatures ◽  
Hydrocyanic Acid ◽  
Quartz Surface ◽  
First Order ◽  
Acid Washing ◽  
Reaction Vessels ◽  
Low Pressures

The decomposition of hydrogen peroxide vapour has been investigated at low pressures (5 to 6 mm.) in the temperature range 50° to 420 °C., for the purpose of determining the effect of the nature and treatment of the active surfaces. The reaction was followed in an all-glass apparatus and, except in one case, with one-litre round flasks as reaction vessels. Soft glass, Pyrex, quartz, and metallized surfaces variously treated were used. In most cases the decomposition was found to be mainly of the first order but the rates varied markedly from one vessel to another, even with vessels made of the same type of glass. On a quartz surface the decomposition was preceded by an induction period at low temperatures. Fusing the glass vessels slowed the reaction considerably and increased its apparent activation energy; this effect was destroyed by acid washing. Attempts to poison the surface with hydrocyanic acid gave no noticeable result. The marked importance of surface effects at all temperatures is considered as an indication that the reaction was predominantly heterogeneous under the prevailing conditions. Values ranging from 8 to 20 kcal. were found for the apparent energy of activation. It is concluded that the decomposition of hydrogen peroxide vapour is not very specific as far as the nature of the catalyst is concerned.

scholarly journals TEMPERATURE CHARACTERISTICS FOR THE METABOLISM OF CHLORELLA

1934 ◽  
Vol 18 (2) ◽  
pp. 209-213 ◽  
Author(s):  
C. S. French
Keyword(s):  
Hydrogen Peroxide ◽  
Low Temperatures ◽  
Temperature Characteristics ◽  
First Order

The decomposition of hydrogen peroxide by intact Chlorella cells follows a first order course at very low temperatures, but at higher temperatures gives falling first order constants. Between 0.6° and 20°C. the value of µ is 10,500 calories.

On the Green-function theory of the spin- Heisenberg ferromagnet

1968 ◽  
Vol 46 (9) ◽  
pp. 1021-1028 ◽  
Author(s):  
S. T. Dembinski
Keyword(s):  
Green Function ◽  
Curie Temperature ◽  
Low Temperatures ◽  
Random Phase Approximation ◽  
Function Theory ◽  
Random Phase ◽  
Exact Result ◽  
Heisenberg Ferromagnet ◽  
First Order ◽  
The Green Function

A new first-order decoupling scheme for the Green function appearing in the theory of the spin-[Formula: see text] Heisenberg ferromagnet is introduced. At low temperatures the magnetization has no spurious term in T3 and the coefficient of the term in T4 is within a few percent of the Dyson exact result. The Curie temperature is equal to the random phase approximation Curie temperature.

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