Condensed Matter Physics, 2022, vol. 25, No. 1, 13702
DOI:10.5488/CMP.25.13702
arXiv:2203.14136
Title:
Theoretical analysis of magnetic properties and the magnetocaloric effect using the Blume-Capel model
Author(s):
 
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S. Oliveira
(Department of Natural Sciences, Federal University of São João del-Rei (UFSJ), Brazil;
Department of Science and Languages, Federal Institute of Education, Science and Technology of Minas Gerais (IFMG), Brazil),
 
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R. H. M. Morais
(Department of Natural Sciences, Federal University of São João del-Rei (UFSJ), Brazil),
 
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J. P. Santos
(Department of Natural Sciences, Federal University of São João del-Rei (UFSJ), Brazil;
Department of Mathematics, Federal University of São João del-Rei (UFSJ), Brazil),
 
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F. C. Sá Barreto
(Emeritus Professor, Department of Physics, Federal University of Minas Gerais (UFMG), Brazil)
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This work investigates the magnetic properties and the magnetocaloric effect in the spin-1 Blume-Capel model. The study was carried out
using the mean-field theory from the Bogoliubov inequality to obtain the expressions of free energy, magnetization and entropy. The
magnetocaloric effect was calculated from the variation of the entropy obtained by the mean-field theory. Due to the dependence on
the external magnetic field and the anisotropy included in the model, the results for the magnetocaloric effect provided the system
with first-order and continuous phase transitions. To ensure the results, the Maxwell relations were used in the intervals where the
model presents continuous variations in magnetization and the Clausius-Clapeyron equation in the intervals where the model presents
discontinuity in the magnetization. The methods and models for the analysis of a magnetic entropy change and first-order and continuous
magnetic phase transitions, such as mean-field theory and the Blume-Capel model, are useful tools in understanding the nature of the
magnetocaloric effect and its physical relevance.
Key words:
magnetocaloric effect, mean-field theory, isothermal entropy change, phase transition, Blume-Capel model
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