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 11.10.2010   Карта сайта     Language По-русски По-английски
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11.10.2010







Room temperature magnetic and magnetocaloric properties of La0.67Ba0.33Mn0.98Ti0.02O3 perovskite





Ma. Oumezzinea, S. Zemnia, Corresponding Author Contact Information, E-mail The Corresponding Author and O. Peñab






a Laboratoire de Physico-chimie des Matériaux, Département de Physique, Faculté des Sciences de Monastir, Monastir 5019, Tunisia


b Sciences Chimiques de Rennes, UMR 6226-CNRS, Université de Rennes 1, 35042 Rennes, Cedex, France





Received 3 June 2010; 


revised 23 August 2010; 


accepted 24 August 2010. 


Available online 8 September 2010.









Abstract



The influence of Ti-doping on the magnetic and magnetocaloric properties of La0.67Ba0.33Mn0.98Ti0.02O3 perovskite is investigated. La0.67Ba0.33Mn0.98Ti0.02O3 sample was prepared by ceramic route at 1400 °C. It is a cubic Pm–3m single phase and exhibits a sharp ferromagnetic–paramagnetic (FM–PM) transition at a Curie temperature TC (314 K) which is very close to room temperature. Above TC the data follow a Curie–Weiss law with a shift between experimental and calculated effective paramagnetic moment. The associated experimental magnetic entropy change (ΔSM) and the relative cooling power (RCP) have been determined. The observed field dependence of ΔSM is explained reasonably well by the Landau theory of second order phase transition. The maximum entropy change View the MathML source exhibits a linear dependence with the applied magnetic field. View the MathML source and RCP are respectively 3.21 J kg−1 K−1 (21.48 mJ cm−3 K−1) and 307 J kg−1 (2054 mJ cm−3) at 5 T, which are about 30% of pure Gd. Our results on the magnetocaloric effect (MCE) are compared favourably with reported values for other doped manganites, thus concluding that our sample can be used as a magnetic refrigerant around room temperature.









Research highlights



right triangle, filled A low doping rate of Ti for Mn in La0.67Ba0.33Mn0.98Ti0.02O3 perovskite tunes the Curie temperature towards room temperature which is suitable for potential applications such as the magnetic refrigeration, based on the magnetocaloric effect, the subject of this work. The maximum value of the magnetic entropy change is View the MathML source (21.48 mJ cm−3 K−1) and its relative cooling power (RCP) is 307 J kg−1 (2054 mJ cm−3) under an applied magnetic field of 5 T, and La0.67Ba0.33Mn0.98Ti0.02O3 can thus be used as an active magnetic refrigerator in a relatively wide range of temperatures nearing 310 K, with a relatively large entropy change. The observed field dependence of ΔSM is explained reasonably well by the Landau theory of second order phase transition.





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