Room temperature multiferroism in La and Ti co-substituted BiFeO 3 nanoparticles M. Gowrishankar a , D. Rajan Babu a,n , P. Saravanan b a Advanced Materials Research Centre, School of Advanced Sciences, VIT University, Vellore 632014, India b Defence Metallurgical Research Laboratory, Hyderabad 500058, India article info Article history: Received 7 November 2015 Received in revised form 10 February 2016 Accepted 11 February 2016 Available online 12 February 2016 Keywords: Multiferroism BiFeO 3 XPS Magnetocapacitance abstract The effect of La and Ti co-substitution on the structural, dielectric, magnetodielectric and ferroelectric properties of sol-gel synthesized Bi 1x La x Fe 1 x Ti x O 3 (for x ¼0, 0.1 and 0.2) nanoparticles were in- vestigated. Rietveld refinement of X-ray diffraction pattern confirmed the phase transition from rhom- bohedral (R3c) to orthorhombic (Pbnm) space group. XPS analysis revealed the existence of Fe as a single state in the co-substituted samples. Temperature dependent dielectric study confirmed that there is an anomaly at the vicinity of Neel temperature for all the compositions. All the co-substituted samples demonstrated a strong magnetodielectric response. & 2016 Elsevier B.V. All rights reserved. 1. Introduction BiFeO 3 (BFO) is one of the multiferroic materials which exhibit both electrical and magnetic ordering above the room tempera- ture. Hence, it is obvious that BFO can be a potential candidate for the applications of transducers, spintronics and photovoltaics [1]. BFO crystallizes in rhombohedral distorted perovskite structure with R3c space group and it has a high Curie temperature (T c )  1100 K and antiferromagnetic Neel temperature (T N )  640 K [2]. Nevertheless, the formation of parasitic phases, poor magneto- electric coupling and high leakage current density hinder BFO for the practical applications [3,4]. Hence, it becomes very much es- sential to reduce the leakage current and to improve the magne- toelectric coupling for the industrial application. Recently, many research groups have reported that A and B site co-substitution is an effective method to enhance the performance of BFO. Dai et al. reported that Eu and Ti co-doped BFO tend to de- crease the leakage current and enhances the magnetization [5]. Hong et al. suggested that Sm and Ti co-substitution in BFO thin film improves dielectric properties and reduces leakage cur- rent [4]. Godara et al. reported that co-doping of Ce and Cr in BFO exhibited a significant increase in the magnetization, ferroelec- tricity and suppression of the leakage current [6]. Similarly, Kumar et al. reported the enhancement in room temperature magneti- zation and the improved electrical behavior of La and Ti co- substituted BFO [7]. La was chosen as a dopant on Bi – site mainly because it suppresses the secondary phases, substantially en- hances the magnetization and improves its dielectric property of BFO [8]. Doping Ti on Fe-site favors the charge compensation by constraining Fe in single oxidation state ( þ 3), thereby reduces oxygen vacancies leading to the decrease in leakage current [9]. To the best of our knowledge, there were no reports on the con- firmation of the oxidation state of Fe, and the temperature de- pendent dielectric study of the La and Ti co-substituted BFO. In the present investigation, we report the co-substitution of La and Ti on BFO synthesized by a sol-gel route. Accordingly, we have employed XPS to confirm the oxidation state of Fe, studied the variation of dielectric constant with respect to temperature and demonstrated strong magneto-dielectric coupling of the co-substituted BFO samples by measuring the capacitance as a function of magnetic field. 2. Experimental method Bi 1 x La x Fe 1 x Ti x O 3 (for x ¼ 0, 0.1 and 0.2) powder was synthe- sized by a facile sol-gel method. For the present investigation, pure and La and Ti co-substituted BFO samples were prepared by dis- solving calculated amount of Bi(NO 3 ) 3 .5H 2 O and La(CH 3 CO 2 ) 3  H 2 O in dil.HNO 3 Fe(NO 3 ) 3 .9H 2 O and Ti[OCH(CH 3 ) 2 ] 4 in deionized water. Both the solutions were mixed under constant stirring. Once the homogeneity was attained, citric acid solution and ethylene glycol were added successively to the precursor solution as the chelating Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters http://dx.doi.org/10.1016/j.matlet.2016.02.044 0167-577X/& 2016 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: rajanbabuphy@gmail.com (D.R. Babu). Materials Letters 171 (2016) 34–37