Magnetic and magnetocaloric properties of lanthanum manganites with monovalent elements doping at A-site
In this study, magnetic and magnetocaloric properties of La 0.8K 0.1M 0.1MnO 3 with M=Na and Ag compounds have been investigated. X-ray diffraction analysis using Rietveld refinement reveals that La 0.8K 0.1Na 0.1MnO 3 and La 0.8K 0.1Ag 0.1MnO 3 samples crystallize in the distorted rhombohedral syst...
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Veröffentlicht in: | Journal of magnetism and magnetic materials 2011, Vol.323 (2), p.252-257 |
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Hauptverfasser: | , , , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | In this study, magnetic and magnetocaloric properties of La
0.8K
0.1M
0.1MnO
3 with M=Na and Ag compounds have been investigated. X-ray diffraction analysis using Rietveld refinement reveals that La
0.8K
0.1Na
0.1MnO
3 and La
0.8K
0.1Ag
0.1MnO
3 samples crystallize in the distorted rhombohedral system with R3¯c space group. The surface morphology and elemental analysis of both samples were carried out by scanning electron microscopy (SEM) and energy dispersive X-ray technique (EDAX), respectively. EDAX spectra taken from the surface of the synthesized powders show a nominal composition near the desired one for M=Na sample whereas some vacancies are present in the A-site in the case of Ag substitution as will be discussed in this paper. Magnetization measurements versus temperature in a magnetic applied field of 50
mT showed that our samples are ferromagnetic at low temperatures. Curie temperature
T
C
is found to be 330 and 310
K for M=Na and Ag, respectively. Arrott plots deduced from isothermal magnetization curves indicate that our samples exhibit a second order magnetic phase transition. From the measured magnetization data of La
0.8K
0.1M
0.1MnO
3 with M=Na and Ag samples as a function of magnetic applied field, the associated magnetic entropy change,
|
Δ
S
M
|
, close to their respective Curie temperature
T
C
and the relative cooling power RCP have been determined. The maximum magnetic entropy change,
|
Δ
S
M
M
a
x
|
, reaches 4.39 and 4.92
J/kg
K for M=Na and Ag, respectively, in a magnetic applied field change of 5
T. For both samples, the
|
Δ
S
M
|
values determined by the Maxwell theory agree well with those calculated by the Landau theory. |
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ISSN: | 0304-8853 |
DOI: | 10.1016/j.jmmm.2010.09.020 |