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

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.

MRS Advances ◽  
2020 ◽  
Vol 5 (51) ◽  
pp. 2639-2645
Author(s):  
Banhi Chatterjee ◽  
Jindřich Kolorenč

AbstractWe investigate whether first-principles calculations with an improved description of electronic correlations can explain the large magnetic moments and the strong magnetocrystalline anisotropy in the ferromagnetic compound UGa2. The correlations are treated within a static mean-field approximation DFT+U combining the density functional theory (DFT) with an onsite Hubbard interaction U. We find that DFT+U improves the agreement of the magnetic moments with the experiment compared to DFT but worsens the theoretical description of the magnetocrystalline anisotropy.


1988 ◽  
Vol 02 (05) ◽  
pp. 577-583 ◽  
Author(s):  
Hidetoshi FUKUYAMA

Implication of mean field approximation to RVB are explored and the temperature dependences of various physical quantities are evaluated. The results are discussed in the light of recent experiments.


2009 ◽  
Vol 18 (04) ◽  
pp. 861-868 ◽  
Author(s):  
V. MARTIN ◽  
L. M. ROBLEDO

The evolution with temperature of nuclear properties relevant to fission are analyzed in the case of the 240 Pu nucleus by using the standard finite temperature mean field approximation (including pairing correlations) and the Gogny D1S force. To be more specific, potential energy curves, pairing correlation energies, level density parameter a, collective quadrupole mass, etc are considered. The impact of their evolution with temperature in the quantum decay rate, meaningful only in the low temperature regime, is also considered.


2021 ◽  
Vol 7 (5) ◽  
pp. 69
Author(s):  
Catherine Cazelles ◽  
Jorge Linares ◽  
Mamadou Ndiaye ◽  
Pierre-Richard Dahoo ◽  
Kamel Boukheddaden

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.


1997 ◽  
Vol 11 (20) ◽  
pp. 867-875 ◽  
Author(s):  
A. A. Rodríaguez ◽  
E. Medina

We study novel geometrical and transport properties of a 2D model of disordered fibre networks. To assess the geometrical structure we determine, analytically, the probability distribution for the number of fibre intersections and resulting segment sizes in the network as a function of fibre density and length. We also determine, numerically, the probability distribution of pore perimeters and areas. We find a non-monotonous behavior of the perimeter distribution whose main features can be explained by solving for two simplified models of the line network. Finally we formulate a mean field approximation to conduction, above the percolation threshold, using the derived results. Relevance of the results to fracture networks will be discussed.


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