Letter Enhanced magnetodielectric properties of single-phase Bi 0.95x La 0.05 Lu x FeO 3 multiferroic system Amit Kumar, K.L. Yadav ⇑ Smart Materials Research Laboratory, Department of Physics, Indian Institute of Technology Roorkee 247667, India article info Article history: Received 20 October 2012 Received in revised form 27 November 2012 Accepted 28 November 2012 Available online 8 December 2012 Keywords: Ceramics Rapid-solidification Magnetization X-ray diffraction abstract Polycrystalline samples of single-phase co-doped (La 3+ , Lu 3+ ) in Bi 0.95x La 0.05 Lu x FeO 3 (x = 0.03, 0.05 and 0.07) (grain size 0.5 lm; tolerance factor 0.88) were prepared by solid state reaction of oxides, followed by rapid quenching of samples. Magnetic measurements show weak ferromagnetic-antiferro- magnetism (WFM) nature at room temperature but ferromagnetic nature at 5 K. Field cooled curves reveal spin reorientation in the system at lower temperature as shown by the peaks at 145 and 140 K for x = 0.03 and 0.07, respectively. Dielectric measurement shows relaxor type of phase transition for x = 0.07. The magnetocapacitance was found to be enhanced (3 times than that of BiFeO 3 ) due to co-doping of (La 3+ , Lu 3+ ) in BiFeO 3 ceramic showing the coupling effect between magnetic and electric behaviors which occurs through the lattice distortion. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Multiferroics are promising materials for design and synthesis of multifunctional materials [1]. They are noteworthy for their un- ique coupling of electric, magnetic and structural order parame- ters, giving rise to simultaneous ferroelectricity, ferromagnetism and ferroelasticity. These materials present opportunities for po- tential applications in information storage, the emerging field of spintronics and sensors. The interaction of electric and magnetic subsystems can manifest itself as the magnetoelectric effect [2]. Although there are a number of materials that possess both ferro- electricity and magnetism, but it is surprising that they do not have a large coupling between them. BiFeO 3 (BFO) is one of the several compounds that exhibits coexistence of ferroelectricity and ferro- magnetism at room temperature, due to its ferroelectric Curie temperature (T C  1103 K) and G-type antiferromagnetic Neel- temperature (T N  647 K) [3]. At the same time, bismuth ferrite (R3c symmetry with rhombohedral structure) is a model mag- neto-electric (ME) perovskite because it presents a number of attractive distinct features compared to other materials: transition temperature above room temperature as well as exchange interac- tions in Fe 3+ sublattice, and the stereo-chemically active 6s 2 lone pair of Bi 3+ , which is the origin of ferroelectricity [4]. There are many methods to synthesize single-phase BiFeO 3 ceramic such as; rapid liquid phase sintering as well as leaching the impurity phase with diluted nitric acid [5]. Since rare-earth metal ions substitutions have led to enhanced magnetism and ferroelectricity in BFO [6], several research groups have attempted to dope with +3 valence lanthanide ions of Pr 3+ , Nd 3+ and Sm 3+ etc. at A site of BFO [6–8]. We have used Lu 3+ as a dopant with the idea that substitution on the A site may play an important role in modifying the crystal structure, on which the resultant magnetism and ferroelectricity of the ceramic is depen- dent [9,10]. La 3+ was used for partial substitution for Bi 3+ at the A site of BFO because La 3+ stabilizes the perovskite phase that helps to decrease Bi volatilization and oxygen vacancies [11]. Keeping this in view we report on structure, magnetic and dielectric properties of polycrystalline samples of co-doped (La 3+ , Lu 3+ ) in BiFeO 3 for the first time. 2. Experimental Polycrystalline samples of BFO and Bi 0.95x La 0.05 Lu x FeO 3 (x = 0.03, 0.05 and 0.07) ceramics were synthesized by solid reaction of mixed oxides, using high purity (99.9%) Bi 2 O 3 (Himedia; Batch No-RM1348), Fe 2 O 3 (Himedia; Batch No-RM5904), La 2 O 3 (Loba Chemie; Batch No-G286007) and Lu 2 O 3 (Himedia; Batch No-RM8564) as starting materials. These materials were grinded for 3 h in acetone medium and pressed uniaxially into disk samples (Pellets) of 7 mm diameter and 1.2 mm thick- ness. The disk samples were dehydrated at 250 °C for 3 h before sintering at a rela- tively high temperature (825 °C) for a short time of 15 min with a high heating rate. Then the pellets were rapidly quenched to room temperature on a copper plate. Pellets were coated with silver paste and used as electrodes for dielectric measure- ment. X-ray diffraction (XRD) was used for phase identification. Fullprof (WinPloter) was used for structure analysis. Field effect scanning electron microscopy (FESEM) was used for analyzing the grain size. Dielectric measurements were carried out using a LCR meter (Model 3532-50, HIKOI) in the temperature range of 35–425 °C at differ- ent frequencies. Quantum designs MPMS system (SQUID magnetometer) was used for magnetic measurements. The magnetocapacitance was observed using a device in which LCR-meter (manufactured by Wayne-Kerr) was interfaced with a magnet. 0925-8388/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2012.11.189 ⇑ Corresponding author. Address: Department of Physics, Indian Institute of Technology, Roorkee 247667, India. Fax: +91 1332 273560. E-mail address: klyadav35@yahoo.com (K.L. Yadav). Journal of Alloys and Compounds 554 (2013) 138–141 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom