Room temperature magnetic and magnetocaloric properties of La 0.67Ba 0.33Mn 0.98Ti 0.02O 3 perovskite

• Published in: Journal of alloys and compounds Vol. 508; no. 2; pp. 292 - 296
• Main Authors: Oumezzine, Ma, Zemni, S., Peña, O.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2010
• Subjects: Chemical synthesis; Magnetic materials; Magnetocaloric effect; Microstructure; Magnetocaloric effect; Magnetic materials; Chemical synthesis; Microstructure
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2010.08.145

▶ A low doping rate of Ti for Mn in La 0.67Ba 0.33Mn 0.98Ti 0.02O 3 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 | Δ S M max | = 3.21   J   k g − 1  K − 1 (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 La 0.67Ba 0.33Mn 0.98Ti 0.02O 3 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 Δ S M is explained reasonably well by the Landau theory of second order phase transition. The influence of Ti-doping on the magnetic and magnetocaloric properties of La 0.67Ba 0.33Mn 0.98Ti 0.02O 3 perovskite is investigated. La 0.67Ba 0.33Mn 0.98Ti 0.02O 3 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 T C (314 K) which is very close to room temperature. Above T C the data follow a Curie–Weiss law with a shift between experimental and calculated effective paramagnetic moment. The associated experimental magnetic entropy change (Δ S M) and the relative cooling power ( RCP) have been determined. The observed field dependence of Δ S M is explained reasonably well by the Landau theory of second order phase transition. The maximum entropy change | Δ S M max | exhibits a linear dependence with the applied magnetic field. | Δ S M max | 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.