CVM Simulation of the Resistivity in L10 and L12 Co-Pt Intermetallic Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
J.M. Sanchez ◽  
M.C. Cadeville ◽  
V. Pierron-Bohnes
Keyword(s):  
Phase Diagram ◽  
Statistical Model ◽  
Temperature Dependence ◽  
Experimental Analysis ◽  
Magnetic Order ◽  
Experimental Studies ◽  
Spin Model ◽  
Spin Disorder ◽  
Magnetic Disorder ◽  
Theory And Experiment

ABSTRACTThe contributions of the atomic and spin disorder to the resistivity of two intermetallic Co1−x Ptx (x=0.5 and 0.7) compounds have been previously determined from experimental studies and separated from the phonon contribution. Now, the atomic and magnetic contributions and their variation with temperature through the Curie and order-disorder transitions are analyzed using a statistical model. The components of the resistivity are described as sums of resistivities of individual tetrahedral clusters. The cluster probabilities are calculated in a magnetic (up and down spin model) CVM approximation, the parameters of which are those that reproduce the experimental Co-Pt phase diagram. The contribution of chemically (magnetically) ordered clusters to the resistivity due to the chemical (magnetic) disorder are taken equal to zero. It is the temperature dependence of all other cluster probabilities which determine the resistivity behavior. Although there are severe approximations in both the experimental analysis and the statistical model, the agreement between theory and experiment is very satisfactory, underscoring the strong interplay between chemical and magnetic order in such ferromagnetic compounds.

Theory and experiment of the temperature dependence of GaAlAs/GaAs HBTs characteristics for power amplifier applications

1995 ◽  
Vol 38 (2) ◽  
pp. 279-286 ◽  
Author(s):  
J.P. Bailbé ◽  
L. Andrieux ◽  
A. Cazarré ◽  
T. Camps ◽  
A. Marty ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Power Amplifier ◽  
Theory And Experiment

scholarly journals Dimer description of the SU(4) antiferromagnet on the triangular lattice

2020 ◽  
Vol 8 (5) ◽  
Author(s):  
Anna Keselman ◽  
Lucile Savary ◽  
Leon Balents
Keyword(s):  
Phase Diagram ◽  
Triangular Lattice ◽  
Ground State ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Spin Model ◽  
Translation Invariance ◽  
Multilayer Graphene ◽  
High Symmetry ◽  
Starting Point

In systems with many local degrees of freedom, high-symmetry points in the phase diagram can provide an important starting point for the investigation of their properties throughout the phase diagram. In systems with both spin and orbital (or valley) degrees of freedom such a starting point gives rise to SU(4)-symmetric models. Here we consider SU(4)-symmetric "spin'' models, corresponding to Mott phases at half-filling, i.e. the six-dimensional representation of SU(4). This may be relevant to twisted multilayer graphene. In particular, we study the SU(4) antiferromagnetic "Heisenberg'' model on the triangular lattice, both in the classical limit and in the quantum regime. Carrying out a numerical study using the density matrix renormalization group (DMRG), we argue that the ground state is non-magnetic. We then derive a dimer expansion of the SU(4) spin model. An exact diagonalization (ED) study of the effective dimer model suggests that the ground state breaks translation invariance, forming a valence bond solid (VBS) with a 12-site unit cell. Finally, we consider the effect of SU(4)-symmetry breaking interactions due to Hund's coupling, and argue for a possible phase transition between a VBS and a magnetically ordered state.

Experimental Studies and Thermodynamic Modeling of the Interaction of O2 with SiC

2002 ◽  
Vol 742 ◽  
Author(s):  
Y. Song ◽  
F. W. Smith
Keyword(s):  
Phase Diagram ◽  
Thermal Decomposition ◽  
High Temperatures ◽  
Thermodynamic Modeling ◽  
Surface Segregation ◽  
Experimental Studies ◽  
Temperature Phase ◽  
Temperature Phase Diagram

ABSTRACTWe report on experimental studies and thermodynamic modeling of the reaction of O2 with the 4H- and 6H-SiC surfaces at high temperatures. This reaction leads to the growth of passivating SiO2 layers at high O2 pressures, etching of the surfaces at lower pressures, and enhancements of the surface segregation of carbon at still lower pressures. A pressure-temperature phase diagram for the oxidation of SiC is presented. Evidence for the thermal decomposition of the SiO2 layer on SiC is also presented.

Field and temperature dependence of intrinsic diamagnetism in graphene: Theory and experiment

2015 ◽  
Vol 91 (9) ◽  
Author(s):  
Zhilin Li ◽  
Lianlian Chen ◽  
Sheng Meng ◽  
Liwei Guo ◽  
Jiao Huang ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Theory And Experiment

scholarly journals Experimental Stability Studies of the Herringbone-Grooved Gas-Lubricated Journal Bearing

1969 ◽  
Vol 91 (1) ◽  
pp. 52-57 ◽  
Author(s):  
Robert E. Cunningham ◽  
David P. Fleming ◽  
William J. Anderson
Keyword(s):  
Journal Bearing ◽  
Experimental Studies ◽  
Ambient Air ◽  
Fair Agreement ◽  
Radial Clearance ◽  
Radial Load ◽  
Test Results ◽  
Stability Studies ◽  
Theory And Experiment

Experimental studies were conducted on six rotors, 1 1/2 in. dia by 12 1/4 in. long operating in ambient air to high compressibility numbers. Herringbone-groove geometries and clearances were varied to determine their effect on half-frequency whirl (HFW). All rotors were operated vertically and without any applied radial load. Results show that half-frequency-whirl onset is very sensitive to radial clearance. Limited test results indicate that a fully grooved bearing is more stable than a partially grooved one, other parameters being equal. Generally fair agreement between theory and experiment was achieved for predicting HFW onset speeds.

Acoustic Speckle: Theory and Experimental Analysis

1979 ◽  
Vol 1 (4) ◽  
pp. 303-324 ◽  
Author(s):  
John G. Abbott ◽  
F. L. Thurstone
Keyword(s):  
Experimental Study ◽  
Experimental Analysis ◽  
Phased Array ◽  
Imaging System ◽  
Experimental Studies ◽  
Laser Speckle ◽  
Speckle Reduction ◽  
Multiple Images ◽  
Starting Point ◽  
Speckle Patterns

A theoretical and experimental study of speckle, as applied to ultrasonic imaging, is presented. The concept of laser speckle is briefly reviewed and is used as a starting point to explain the origin of acoustic speckle. The primary differences between these two phenomena are discussed and are confirmed by experiment. An experimental study of speckle reduction by summation of multiple images is also presented. Several techniques for generating independent speckle patterns for use in image summation schemes are proposed. A phased array, dynamically focused sector imaging system was used in all of the experimental studies reported.

Thermal Properties of CuGa2 Phase in Inert Atmosphere

2012 ◽  
Vol 326-328 ◽  
pp. 227-232 ◽  
Author(s):  
T.V. Kulikova ◽  
V.A. Bykov ◽  
K. Y. Shunyaev ◽  
A.B. Shubin
Keyword(s):  
Thermal Analysis ◽  
Phase Diagram ◽  
Thermal Decomposition ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
Experimental Studies ◽  
Inert Atmosphere ◽  
Heat Conductivity Coefficient ◽  
Incongruent Melting ◽  
Modeling Methods

Thermal decomposition of copper digallide was studied using experimental (thermal analysis) and theoretical (thermodynamic modeling) methods. The temperatures of CuGa2incongruent melting are in satisfactory agreement between experimental and calculated values. Small differences with the phase diagram can be explained by minor non-stoichiometry of the alloy samples. The experimental studies of thermal diffusivity and thermal expansion of CuGa2were performed in the temperature range 298-500 K. The heat conductivity coefficient was further calculated using literary data concerning the density and heat capacity of the copper digallide.

QUANTUM DISORDER OF AN ANTIFERROMAGNETIC SPIN MODEL ON THE SIERPIŃSKI GASKET

2003 ◽  
Vol 17 (28) ◽  
pp. 5059-5063
Author(s):  
ANDREAS VOIGT ◽  
JOHANNES RICHTER
Keyword(s):  
Ground State ◽  
Magnetic Order ◽  
Spin Exchange ◽  
Sierpinski Gasket ◽  
Spin Model ◽  
Sierpiński Gasket ◽  
Spin Correlations ◽  
Quantum Antiferromagnet ◽  
Antiferromagnetic Spin ◽  
Exact Diagonalisation

We study the ground state magnetic order of the quantum antiferromagnet on the fractal Sierpiński gasket, a system with a dimension between one and two. Using exact diagonalisation we analyse the ground state and thermodynamic properties of small finite systems and calculate data like spin-spin correlations and specific heat. We find arguments that the ground state remains disordered for an XY or Ising like anisotropy in the spin exchange away from the isotropic Heisenberg point.

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