Dielectric, ferroelectric, magnetic and magnetoelectric properties of PMN-PT based ME composites Arif D. Sheikh, V.L. Mathe n Novel Materials Research Laboratory, Department of Physics, University of Pune, Pune 411007, India article info Article history: Received 4 March 2010 Received in revised form 9 July 2011 Accepted 11 August 2011 Available online 30 August 2011 Keywords: C. X-ray diffraction D. Dielectric properties D. Ferroelectricity D. Magnetic properties abstract A systematic study of magnetoelectric composite system (x) CoFe 2 O 4 þ(1 x) Pb(Mg 1/3 Nb 2/3 ) 0.67 Ti 0.33 O 3 with x ¼0, 0.15, 0.30, 0.45 and 1 was carried out. The lattice strain was calculated using Williamson and Hall equation, which depends on the content of constituent phases in composites. The microstructure was studied using scanning electron microscopy. The ferroelectric transition temperature was independent of the content of individual phases, suggesting that the ferroelectric character is maintained in the composite. Observed P–E and M–H loops indicate that the multiferroic nature of magnetoelectric ceramics is dependent on the content of individual phases. The variation of magnetostriction with dc magnetic field was studied. The maximum magnetoelectric voltage coefficient of 7.2 mV/cm Oe is obtained for the synthesized composites. The magnetoelectric measurements are well explained with magnetostrictive behavior of the magnetic phase. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction Multiferroic materials have drawn an ever increasing interest due to their attractive multifunctional features and potential applications in multifunctional devices such as transducers, actuators and sensors [1, 2]. In multiferroics, the coupling interaction between the different order parameters could produce new effects, such as magnetoelectric (ME) effect [3, 4]. Such materials can display not only ferroelectric and magnetic properties simultaneously but also a coupling effect between the electric and magnetic polarizations, that is, a sponta- neous electric polarization induced by an external magnetic field or a magnetization induced by an applied electric field i.e., ME effect [5]. Few single phase ME materials exhibit inherent coupling in multi- ferroic order parameters and produce a weak ME signal, which hinders their device applications. The coupling interaction between ferroelectric and piezomagnetic phases with high values of piezo- electric and magnetostrictive coefficients, respectively, could pro- duce better ME response than that of the single phase ME materials. Bulk composites have the advantage of superior mechanical strength over layered samples. One could easily control physical, magnetic, dielectric and ME parameters with proper choice of two phases and their content. Several groups studied widely on various aspects of ME composites including piezoelectric and piezomagnetic phases, because of simplicity in synthesis using conventional ceramic processing [6–13]. Nan et al. reported that a large ME voltage coefficient of about 80 mV cm 1 Oe 1 was observed for 0.32 NiFe 2 O 4 /0.68 PZT particulate composite [14]. Chen reported that the maximum value of (dE/dH), of about 24.8 mV/cm Oe 1 for CoFe 2 O 4 /Sr 0.5 Ba 0.5 Nb 2 O 6 particulate composites [15]. Duong et al. reported highest value of ME coefficient of about 3.4 mV/cm Oe 1 for CoFe 2 O 4 –BaTiO 3 multiferroic composite [16]. Sarah and Suryanarayana reported a maximum ME output of about 15 mV/cm/Oe for 40 LiFe 2 O 4 :60 BT composites [17]. Sun et al. reported that a maximum ME voltage coefficient of 13.1 mV/cm Oe is obtained in the 0.1NZCF/0.9PNN-PZN-PNW-PT composite at 400 Oe dc magnetic bias field superimposed 1 kHz magnetic field with 5 Oe amplitude [18]. Recently Kanamadi et al. have reported that max- imum magnetoelectric voltage coefficient of about 0.826 mV/cm Oe was observed for the x ¼ 0.15 composite at room temperature [19]. Literature [6–19] suggests that selection of individual phases affects the magnetoelectric character of the composite. In order to enhance the magnetoelectric coupling the individual phases should possess large magnetostrictive and piezoelectric coefficients with comparable resistivities. Recently, the high piezoelectric constant was observed in PMN-PT ceramics that enhanced the ME output significantly [4, 13]. Hence Pb(Mg 1/3 Nb 2/3 ) 0.67 Ti 0.33 O 3 (PMN-PT) in morphotropic phase boundary (MPB) region was selected as a ferroelectric phase due to its strongest piezoelectric effect among various piezoelectric materials whereas CoFe 2 O 4 [CFO] was used as a magnetic phase due to its high magnetostriction values among other ferrites. 2. Experimental The CFO phase was prepared using conventional ceramic technique. The Co CO 3 , Fe 2 O 3 was used as the starting material Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jpcs Journal of Physics and Chemistry of Solids 0022-3697/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpcs.2011.08.011 n Corresponding author. Fax: þ91 20 25691684. E-mail address: vlmathe@physics.unipune.ernet.in (V.L. Mathe). Journal of Physics and Chemistry of Solids 72 (2011) 1423–1429