Large magnetocaloric entropy change at room temperature in soft ferromagnetic manganites

In this paper, La 0.75 Ca 0.25− x Na x MnO 3 ( x = 0.15 and 0.20) samples were prepared by the flux method. Crystallographic study revealed that the x = 0.15 sample is characterized by the coexistence of a mixture of orthorhombic and rhombohedral structures with Pbnm and R 3&cmb.macr; c space gr...

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Bibliographic Details
Published in:RSC advances 2019-01, Vol.9 (1), p.65-76
Main Authors: Bouzidi, Souhir, Gdaiem, Mohamed Amara, Dhahri, J, Hlil, E. K
Format: Article
Language:English
Subjects:
Chemistry
Coercivity
Condensed Matter
Crystallization
Crystallography
Entropy
Ferromagnetism
Magnetic fields
Magnetic properties
Magnetic recording
Magnetism
Materials Science
Memory devices
Phase transitions
Physics
Refrigerators
Room temperature
Temperature dependence
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Summary:In this paper, La 0.75 Ca 0.25− x Na x MnO 3 ( x = 0.15 and 0.20) samples were prepared by the flux method. Crystallographic study revealed that the x = 0.15 sample is characterized by the coexistence of a mixture of orthorhombic and rhombohedral structures with Pbnm and R 3&cmb.macr; c space groups, respectively. While, the x = 0.20 sample crystallized in the rhombohedral structure with a R 3&cmb.macr; c space group. Magnetic data, under a magnetic field of 0.05 T, indicated that our samples undergo a ferromagnetic (FM)-paramagnetic (PM) phase transition, on increasing the temperature. The magnetic field dependence of the magnetocaloric properties of La 0.75 Ca 0.25− x Na x MnO 3 ( x = 0.15 and 0.20) samples, with the second phase transition, was investigated. Near room temperature, the x = 0.20 sample exhibited a large magnetic entropy change with maxima of 6.01 and 3.12 J kg −1 K −1 , respectively, under applied magnetic fields of 5 and 2 T. Also, the relative cooling power (RCP) was calculated. According to hysteresis cycles, for our studied samples, at 10 K a typical soft FM behavior with a low coercive field was observed. These results make our samples promising candidates for magnetic refrigerators, magnetic recording, and memory devices. -Δ S M as a function of temperature at different μ 0 H fields, for x = 0.20 compound. The red line curves represent the modeled data and symbols are the experimental data.
ISSN:2046-2069
2046-2069
DOI:10.1039/c8ra09166h