Contents lists available at ScienceDirect Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm Research articles Enhanced multiferroic response in new binary solid solution (0.5) Bi 0.70 A 0.30 FeO 3 –(0.5)PbTi 0.5 Fe 0.5 O 3 (A = Sr, Pb, and Ba) systems Mehak Shariq a , Shahzad Hussain a, ⁎ , Mohsin Rafique a , M. Naveed-Ul-Haq b , Azizur Rehman c a Magnetism Laboratory, Department of Physics, COMSATS University Islamabad, Islamabad Campus, 45550, Pakistan b Department of Physics, COMSATS University Islamabad, Lahore Campus, 54000, Pakistan c Department of Physics, University of Science and Technology of China, Hefei 230026, China ABSTRACT New (0.5)Bi 0.70 A 0.30 FeO 3 –(0.5)PbTi 0.5 Fe 0.5 O 3 (A = Sr 2+ , Pb 2+ , and Ba 2+ ; denoted as A30-Fe50) binary solid solutions with multiferroic properties were synthesized via solid-state method. X-ray diffraction and a subsequent Rietveld analysis of the data for solid solutions confirmed the presence of multiphase (R3c, Pm m 3 ¯ & P4mm) in the binary systems. Deconvoluted Raman spectra helped us to understand the variation of phonon modes. The overlapping and weakening of modes are ascribed to the structural changes/transformation whereas modes’ shifting is attributed to the changes in average atomic mass at A/B-sites. The magnetic properties of the binary systems showed an increase in average magnetization. We found a systematic increase in magnetization of binary systems which correlates well with the size variance (r i ; Ba 2+ > Pb 2+ > Sr 2+ > Bi 3+ )effect introduced in BiFeO 3 phase and the highest magnetization was observed for Ba30-Fe50 binary system. Moreover, Pb30- Fe50 and Ba30-Fe50 systems exhibited enhanced magnetization compared to the sum of constituent phases while the Sr30-Fe50 system exhibited the average trend of saturation magnetization. This improvement in magnetic properties of solid solutions can be attributed to the suppression of spin spiral modulated structure as well as possible changes in FeeO local environment which effects the superexchange interaction. Moreover, Pb30-Fe50 binary system exhibited improved dielectric and ferroelectric properties which can be attributed to the existence of lone pair ion Pb which has high polarizability and a higher percentage of tetragonal symmetry in the system. Thus, a significantly high magnetization, high value of dielectric constant, small dielectric loss, and a good ferroelectric response of Pb30-Fe50 system makes it the best among the three studied systems and a promising candidate from an application point of view. 1. Introduction Ferroelectricity is observed in perovskite oxides because their structure can support deformations which lead to the appearance of a permanent electric polarization. There are a very small number of perovskite materials, called multiferroics, which can contain simulta- neous ferroelectricity and some kind of ferromagnetism. This scarcity of single-phase multiferroic compounds is believed to arise from the fact that it is impossible to find compounds with partially filled d-orbitals which are required for ferromagnetism and at the same time, empty d- shells are necessary for cation off-center displacement responsible for ferroelectricity [1]. In such materials, the origin of ferroelectricity can be controlled by different mechanisms such as by lone pair mechanism, change in geometrical arrangements, and absence of inversion sym- metry due to spiral magnetic ordering [2]. BiFeO 3 (BFO) is one of the perovskite oxides which possesses two types of long-range order: (i) ferroelectric ordering temperature is 1103 K, and (ii) antiferromagnetic ordering temperature is 640 K [3,4]. A significantly large difference between two ordering temperatures implies that different mechanisms are accountable for spin and electric polarizations. Here, B-site Fe 3+ ions are responsible for magnetism whose d 5 -electronic configuration result in an effective magnetic mo- ment of 5.9 μ B whereas the stereochemical activity of A-site Bi 3+ ions with 6 s lone pair electrons is responsible for the ferroelectricity [5–7]. Neutron scattering experiments have established that antiferromagnetic spins are not collinear rather they are slightly canted thereby leading to a weak magnetization [6]. However, in bulk form, the weak magneti- zation present due to a canted structure is canceled in the presence of spiral spin modulated structure (SSMS) having 62 nm length resulting in zero net magnetization. The line shape analysis of nuclear magnetic spin resonance has confirmed the existence of SSMS [8]. The integration of bulk BFO into practical devices has been hin- dered due to several issues which include weak magnetic response, very high coercive magnetic field, low electric resistivity which results in high leakage current, low value of dielectric constant, lossy polarization versus electric field (PE) loops, low piezoelectric properties, and weak magnetoelectric coupling [9]. Several attempts have been made to address the above-mentioned issues which include the rational synth- esis of phase pure BFO nanoparticles, strain-engineered BFO thin films, and the imposition of structural medication to suppress/destroy the SSMS [10]. In case of the doped systems, rare earth (La 3+ , Nd 3+ , Dy 3+ , Pr 3+ etc.) substitution at Bi-site in BFO has proven to be an effective https://doi.org/10.1016/j.jmmm.2019.165685 Received 19 February 2019; Received in revised form 11 July 2019; Accepted 8 August 2019 ⁎ Corresponding author. E-mail address: shahzad.hussain@comsats.edu.pk (S. Hussain). Journal of Magnetism and Magnetic Materials 492 (2019) 165685 Available online 09 August 2019 0304-8853/ © 2019 Elsevier B.V. All rights reserved. T