scholarly journals Hexagonal-Shaped Spin Crossover Nanoparticles Studied by Ising-Like Model Solved by Local Mean Field Approximation

2021 ◽  
Vol 7 (5) ◽  
pp. 69
Author(s):  
Catherine Cazelles ◽  
Jorge Linares ◽  
Mamadou Ndiaye ◽  
Pierre-Richard Dahoo ◽  
Kamel Boukheddaden
Keyword(s):  
Spin Crossover ◽  
Hexagonal Lattice ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Ligand Field ◽  
Order And Disorder ◽  
The Matrix ◽  
Local Mean ◽  
Parameter Values

The properties of spin crossover (SCO) nanoparticles were studied for five 2D hexagonal lattice structures of increasing sizes embedded in a matrix, thus affecting the thermal properties of the SCO region. These effects were modeled using the Ising-like model in the framework of local mean field approximation (LMFA). The systematic combined effect of the different types of couplings, consisting of (i) bulk short- and long-range interactions and (ii) edge and corner interactions at the surface mediated by the matrix environment, were investigated by using parameter values typical of SCO complexes. Gradual two and three hysteretic transition curves from the LS to HS states were obtained. The results were interpreted in terms of the competition between the structure-dependent order and disorder temperatures (TO.D.) of internal coupling origin and the ligand field-dependent equilibrium temperatures (Teq) of external origin.

scholarly journals 2D Spin Crossover Nanoparticles described by the Ising-like model solved in Local Mean-Field Approximation

2017 ◽  
Vol 936 ◽  
pp. 012052
Author(s):  
Salah Eddine Allal ◽  
Jorge Linares ◽  
K. Boukheddaden ◽  
Pierre Richard Dahoo ◽  
F. de Zela
Keyword(s):  
Spin Crossover ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Local Mean

scholarly journals Three states and three steps simulated within Ising like model solved by local mean field approximation in 3D spin crossover nanoparticles

2021 ◽  
Vol 26 ◽  
pp. 102074
Author(s):  
Catherine Cazelles ◽  
Yogendra Singh ◽  
Jorge Linares ◽  
Pierre-Richard Dahoo ◽  
Kamel Boukheddaden
Keyword(s):  
Spin Crossover ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Local Mean

Spin crossover in an elastic chain of exchange clusters beyond mean field approximation

2010 ◽  
Vol 12 (41) ◽  
pp. 13667 ◽  
Author(s):  
Vitaly Morozov ◽  
Nikita Lukzen ◽  
Victor Ovcharenko
Keyword(s):  
Spin Crossover ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation

scholarly journals Thermoviscoelastic Analysis of Concrete Creep at Mesoscale

2016 ◽  
Vol 711 ◽  
pp. 652-658 ◽  
Author(s):  
Benoit Bary ◽  
Christophe Bourcier ◽  
Thomas Helfer
Keyword(s):  
Creep Behavior ◽  
Mean Field ◽  
Heterogeneous Material ◽  
Field Approximation ◽  
Approximation Schemes ◽  
Mean Field Approximation ◽  
Concrete Creep ◽  
Linear Elastic ◽  
The Matrix ◽  
Aggregate Shape

Concrete is a heterogeneous material made up at mesoscale of linear elastic aggregates distributed in a mortar matrix whose behavior is time and temperature dependent. The Interfacial Transition Zone (ITZ) between aggregates and matrix also influences the overall behavior. We investigate here analytically and numerically by means of 3D simulations the creep behavior of concrete and mortar subjected to moderate temperatures at mesoscale. The numerical specimens consist in unstructured periodic meshes of polyhedral aggregates with various size and shapes randomly distributed in a box. Specific interface finite elements are introduced between aggregates and matrix to model the ITZ. Both matrix and ITZ are considered as linear thermoviscoelastic materials. Averaged stresses and strains in the matrix and aggregate phases are compared to analytical estimations obtained with classical mean-field approximation schemes applied in the Laplace-Carson space, where the ITZ are introduced via imperfect interfaces modelled with the Linear Spring Model (LSM). The effects of ITZ thickness, aggregate shape and temperature are then studied to evaluate their respective influence on mortar and concrete creep behavior.

scholarly journals WRITING ELECTRONIC FERROMAGNETIC STATES IN A HIGH-TEMPERATURE PARAMAGNETIC NUCLEAR SPIN SYSTEM

2011 ◽  
Vol 09 (04) ◽  
pp. 1047-1056 ◽  
Author(s):  
D. O. SOARES-PINTO ◽  
J. TELES ◽  
A. M. SOUZA ◽  
E. R. DEAZEVEDO ◽  
R. S. SARTHOUR ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Mean Field ◽  
Field Approximation ◽  
Order Transition ◽  
Mean Field Approximation ◽  
Temperature Hysteresis ◽  
First Case ◽  
The Matrix ◽  
The Mean

In this paper, we use Nuclear Magnetic Resonance (NMR) to write electronic states of a ferromagnetic system into high-temperature paramagnetic nuclear spins. Through the control of phase and duration of radio frequency pulses, we set the NMR density matrix populations, and apply the technique of quantum state tomography to experimentally obtain the matrix elements of the system, from which we calculate the temperature dependence of magnetization for different magnetic fields. The effects of the variation of temperature and magnetic field over the populations can be mapped in the angles of spin rotations, carried out by the RF pulses. The experimental results are compared to the Brillouin functions of ferromagnetic ordered systems in the mean field approximation for two cases: the mean field is given by (i) B = B0 + λM and (ii) B = B0 + λM + λ′M3, where B0 is the external magnetic field, and λ, λ′ are mean field parameters. The first case exhibits second order transition, whereas the second case has first order transition with temperature hysteresis. The NMR simulations are in good agreement with the magnetic predictions.

New statistical lattice model with double honeycomb symmetry

2014 ◽  
Vol 28 (15) ◽  
pp. 1450086 ◽  
Author(s):  
S. Naji ◽  
A. Belhaj ◽  
H. Labrim ◽  
M. Bhihi ◽  
A. Benyoussef ◽  
...  
Keyword(s):  
Ground State ◽  
Lattice Model ◽  
Present Model ◽  
Hexagonal Lattice ◽  
Mean Field ◽  
Field Approximation ◽  
Hexagonal Structure ◽  
Mean Field Approximation ◽  
Two Dimensional Materials ◽  
The Mean

Inspired from the connection between Lie symmetries and two-dimensional materials, we propose a new statistical lattice model based on a double hexagonal structure appearing in the G2 symmetry. We first construct an Ising-1/2 model, with spin values σ = ±1, exhibiting such a symmetry. The corresponding ground state shows the ferromagnetic, the antiferromagnetic, the partial ferrimagnetic and the topological ferrimagnetic phases depending on the exchange couplings. Then, we examine the phase diagrams and the magnetization using the mean field approximation (MFA). Among others, it has been suggested that the present model could be localized between systems involving the triangular and the single hexagonal lattice geometries.

The Determination of the Magnetoelectric Coupling Coefficient in Ferroelectric–Ferromagnetic Composite Based on PZT–Ferrite

2013 ◽  
Vol 58 (4) ◽  
pp. 1401-1403 ◽  
Author(s):  
J.A. Bartkowska ◽  
R. Zachariasz ◽  
D. Bochenek ◽  
J. Ilczuk
Keyword(s):  
Dielectric Permittivity ◽  
Coupling Coefficient ◽  
Mean Field ◽  
Field Approximation ◽  
Theoretical Description ◽  
Magnetoelectric Coupling ◽  
Mean Field Approximation ◽  
Dielectric Measurements ◽  
Temperature Dependences ◽  
Multiferroic Composite

Abstract In the present work, the magnetoelectric coupling coefficient, from the temperature dependences of the dielectric permittivity for the multiferroic composite was determined. The research material was ferroelectric-ferromagnetic composite on the based PZT and ferrite. We investigated the temperature dependences of the dielectric permittivity (") for the different frequency of measurement’s field. From the dielectric measurements we determined the temperature of phase transition from ferroelectric to paraelectric phase. For the theoretical description of the temperature dependence of the dielectric constant, the Hamiltonian of Alcantara, Gehring and Janssen was used. To investigate the dielectric properties of the multiferroic composite this Hamiltonian was expressed under the mean-field approximation. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified.

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