Effect of potassium doping on the structural, magnetic and magnetocaloric properties of La0.7Sr0.3−xKxMnO3 perovskite manganites |
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Authors: | W Cheikh-Rouhou Koubaa M Koubaa A Cheikhrouhou |
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Affiliation: | aLaboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, B.P. 802, Sfax, Tunisia;bLaboratoire Louis NEEL, CNRS, B.P. 166, 38042 Grenoble cedex9, France |
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Abstract: | We investigate the effect of potassium doping on the structural, magnetic and magnetocaloric properties of La0.7Sr0.3−xKxMnO3 (x = 0.05, 0.1, 0.15 and 0.2) powder samples. Our polycrystalline compounds were synthesized using the solid-state reaction at high temperature. X-ray diffraction characterizations showed that all our studied samples crystallize in the distorted rhombohedral system with space group. With increasing potassium content, the unit cell volume exhibits a broad maximum around x = 0.15. Magnetization measurements versus temperature showed that all our samples exhibit a paramagnetic to ferromagnetic transition with decreasing temperature. The Curie temperature TC is found to decrease from 365 K for x = 0 to 328 K for x = 0.2 as well as the saturated magnetization Msp which shifts from 3.68 μB/Mn for x = 0 to 3.05 μB/Mn for x = 0.2. The critical exponent γ defined as Msp (T) = Msp(0)1−(T/TC)]γ is found to remain almost constant and equal to 0.33 for all our samples. The maximum of magnetic entropy changes |ΔSmax| of La0.7Sr0.3−xKxMnO3 for x = 0.05 and 0.15 is found to be respectively, 1.37 and 1.2 J kg−1 K−1 under a magnetic field change of 1 T. |
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Keywords: | Manganites Ferromagnetism Curie temperature Magnetocaloric effect |
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