Non-equilibrium thermodynamics and entropy production spectra: A tool for the characterization of ferrimagnetic materials

Abstract

An analysis of entropy production and its evolution in the frequency domain upon application of electromagnetic fields to ferrimagnetic material has been investigated. The spectral entropy of NiZn ferrites doped with different amounts of Yttrium has been studied by numerical simulation. Under the application of an oscillating electromagnetic field, the system is out of equilibrium as there is entropy production due to the dielectric and magnetic polarization. A system subjected to electromagnetic fields E.!/ and H.!/ at constant temperature T has been considered. For the numerical simulation of the behavior of the entropy production due to magnetic relaxation, experimental data have been correlated to a recently published causality model. For the entropy production due to dielectric relaxation, experimental data have been used. Entropy production related to magnetic response could be associated with two mechanisms: domain wall motion and spin rotation. Entropy production related to dielectric processes could be associated with the delay of the different components of the polarizability as a function of the frequency of the applied field and the correlation with the transport charge mechanism in the material. At the frequency range under study, the entropy production due to dielectric relaxation is negligible. Thus entropy spectra could be a suitable tool for the analysis of the ferrimagnetic materials. 176

Numerical response and causality study of the magnetic permeability-frequency function of NiZn ferrites using Genetic Algorithm

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Modeling and Analysis of Entropy Generation in Light Heating of Nanoscaled Silicon and Germanium Thin Films

“…They were obtained from Equations (A1) and (A2) and (A34) with Equations (A26)-(A28) and (B1) and the dimensional analysis found in Appendix C. The continuity and energy conservation dimensional equations for the stationary state read as follows: . This is the reason why the term G R − does not appear in Equations 1and (2). The complete reduced equations can be seen in Appendix C.…”

“…Equations (4)-(8) are obtained. First we note that the temperature field becomes decoupled from Equations (1) and (2). We then find an analytical solution of Equation (3) for the stationary state, obtained with Wolfram Mathematica 10.0, where the source term is taken from Equations (B1).…”

“…Development of new thermoelectric materials for that purpose has been rapid in past few years. The analysis of entropy production is being used to characterize materials as, for instance, in the case of ferromagnetic materials under the application of oscillating electromagnetic fields [2] or in the case of thermoelectric materials in thermal oscillating regimes [3,4]. The study of dissipation and irreversibility in different processes in physics and engineering is in the above context a useful tool to found optimization procedures.…”