Structural Analysis and Theoretical Investigations of the Magnetocaloric Effect for La 0.7 Ba 0.15 Ag 0.15 MnO 3 Mangani
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ORIGINAL PAPER
Structural Analysis and Theoretical Investigations of the Magnetocaloric Effect for La0.7Ba0.15Ag0.15MnO3 Manganite Prepared Using Sol-Gel Route Sobhi Hcini 1 & Mohamed Hsini 2 & Hussein Al Robei 3 & Mohamed Lamjed Bouazizi 3 & Michel Boudard 4 Received: 5 May 2020 / Accepted: 18 July 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Structural analysis, magnetocaloric properties, and theoretical investigations of the magnetocaloric effect were carried out in the crystalline La0.7Ba0.15Ag0.15MnO3 manganite prepared using sol-gel route. The phase purity and structure of this sample were checked by X-ray diffraction technique and Rietveld analysis. From magnetic measurements, the ferromagnetic to paramagnetic (FM-PM) phase transition was observed around TC = 255 K. The maximum change in magnetic entropy (ΔS max M ) and relative cooling power (RCP) extracted from magnetic measurements were 3.48 J × kg-1 × K-1 and 225 J × kg-1 at an applied magnetic field of 5 T. These magnetocaloric parameters offer to the sample the possible use in the magnetic refrigeration technology. The magnetic entropy simulation by using different theories such as the Weiss molecular mean-field theory and the Landau theory shows good correlation between the theoretical values of −ΔSM(T) and the experimental ones estimated from Maxwell relation. Keywords Manganites . Sol-gel route, . Structural analysis . Magnetocaloric effect . Spontaneous magnetization, . Theoretical models
1 Introduction The magnetic refrigeration (MR) seems to be one of the very serious alternatives for replacing conventional refrigeration systems based on compression-expansion of gases [1]. This new technique, compared with the traditional techniques, has several advantages. It is more energy efficient, more compact, and above all less harmful to the environment. The MR relies on the MCE (magnetocaloric effect), which is an intrinsic property of * Sobhi Hcini [email protected] 1
Research unit of valorization and optimization of exploitation of resources, Faculty of Science and Technology of Sidi Bouzid, Kairouan University, 9100 Sidi Bouzid, Tunisia
2
Laboratory of Physical Chemistry of Materials, Physics Department, Faculty of Sciences of Monastir, Monastir University, 5019 Monastir, Tunisia
3
Department of Mechanical Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Alkharj 11942, Saudi Arabia
4
LMGP, CNRS, University of Grenoble Alpes, 38000 Grenoble, France
magnetic materials and results in an instantaneous and reversible variation of their temperature and entropy when they are subjected to a variation of magnetic field. This reversible effect is maximal at the FM-PM transition temperature (called the Curie temperature TC), and is the consequence of the decrease in magnetic entropy following the alignment of the electronic spins under the application of the magnetic field. However, the optimization of the magnetic refrigerator devices depends on a solid thermodynamic description of
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