Journal of Alloys and Compounds 508 (2010) 292–296 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom Room temperature magnetic and magnetocaloric properties of La 0.67 Ba 0.33 Mn 0.98 Ti 0.02 O 3 perovskite Ma. Oumezzine a , S. Zemni a,∗ , O. Pe ˜ na b 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 article info Article history: Received 3 June 2010 Received in revised form 23 August 2010 Accepted 24 August 2010 Available online 8 September 2010 Keywords: Chemical synthesis Microstructure Magnetic materials Magnetocaloric effect abstract The influence of Ti-doping on the magnetic and magnetocaloric properties of La 0.67 Ba 0.33 Mn 0.98 Ti 0.02 O 3 perovskite is investigated. La 0.67 Ba 0.33 Mn 0.98 Ti 0.02 O 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) transi- tion 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 (S M ) and the relative cooling power (RCP) have been determined. The observed field dependence of S M is explained reasonably well by the Landau theory of second order phase transition. The maximum entropy change |S max M | exhibits a linear dependence with the applied magnetic field. |S max M | 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. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Magnetic refrigeration (MR) technology, based upon the magne- tocaloric effect (MCE), is required near room temperature and is of particular interest considering the potential impact on energy sav- ings and environmental protection. Gd is considered as a prototype material for such purpose, with a large MCE near its Curie temper- ature (293 K) [1,2]. But its usage is somehow commercially limited because the cost of Gd is quite expensive ∼$4000/kg. Recently, an intense interest in perovskite-type manganese oxides (the so- called manganites) R 1-x M x MnO 3 (where R is a rare earth ion and M is a divalent alkali) is prompted by the observation of colossal magnetoresistance (CMR) [3–5]. Because of some advantages over Gd and intermetallic alloys, such as low production cost, chemical stability, high resistivity (minimum Eddy current loss) [6] and not affected by corrosion, manganites have attracted more attention as alternative candidates for magnetic refrigeration in the vicin- ity of room temperature. La 0.67 Ba 0.33 MnO 3 perovskite compound has a relatively high Curie temperature (T C ≈ 350 K [7]). Potential applications, particularly the magnetic refrigeration (MR) require having transition temperatures T C close to room temperature. This ∗ Corresponding author. E-mail address: zemnis@yahoo.fr (S. Zemni). can be achieved by an appropriate amount of oxygen stoichiom- etry [8] or by substitution of Mn by a non-magnetic cation such as titanium. In this work we have investigated the magnetic and magnetocaloric properties of Ti-doped La 0.67 Ba 0.33 Mn 0.98 Ti 0.02 O 3 manganites. Theoretical modeling of the MCE is used in order to compare the experimental (-S M ) curve and the estimated one using Landau theory. 2. Experimental Polycrystalline La0.67Ba0.33Mn1-xTixO3 (x = 0, 0.02) samples were synthesized by solid-state reaction route at 1400 ◦ C, using (Mn + Ti)/(La + Ba) ratio equal to 1 as reported elsewhere for La0.67Ba0.33Mn1-xTixO3 (0 ≤ x ≤ 0.3) manganites [9]. Pow- der X-ray diffraction (XRD) analysis was carried out in Bragg–Brentano geometry with a “PANalytical X’Pert Pro” diffractometer with filtered (Ni filter) Cu radia- tion. Data for the Rietveld refinement were collected in the 2 range of 10–100 ◦ with a step size of 0.017 ◦ and a counting time of 18 s per step. Scanning electron microscopy (SEM) was used to determine grain size and morphology of the sam- ple. Energy dispersive X-ray fluorescence (EDX) analysis was used to determine chemical homogeneity and cations composition. Quantitative analyses of chemical elements, including the oxygen content, were performed by inductively coupled plasma atomic emission spectroscopy (ICPAES) techniques. Magnetization (M) vs. temperature (T) and magnetization vs. magnetic field (0H) were measured using a MPMS-XL5 quantum design SQUID susceptometer. M(T) data were obtained in 2–400 K temperature range with applied magnetic field of 0.01 T in field cooled (FC) and zero field cooled (ZFC) regimes. Isothermal M(H) data were measured in 230–390 K temperature range by a step of 10 K under an applied magnetic field varying from 0 to 5 T. 0925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2010.08.145