Structural, Magnetic, and Magnetodielectric Properties of Bi-Based Modified Ceramic Composites

Abstract

In this chapter, we introduce a promising composite material, which can be used as a potential candidate in the field of charge storage, sensors, and spintronic devices. The structural, magnetic, and magnetodielectric properties of the pure cum composite samples are investigated. The Rietveld refinement of the X-ray data confirmed the presence of a single (A21am) and mixed phases (A21am + R-3c + Pbam) in the pure and composite sample, correspondingly. The SEM microstructure suggests the contrasting nature of the homogeneous and heterogeneous distribution of grains in the corresponding pure and composite sample. The magnetic properties of the composite sample increase due to the enhanced exchange interaction between the different magnetic ions. The frequency-dependent dielectric subjected to a constant magnetic field indicates the signature of magnetodielectric (MD) coupling for both the samples. The field variation of the MD loop shows the symmetric hysteresis loop in the composite due to the addition of magnetostrictive La0.67Sr0.33MnO3 and the non-collinear antiferromagnetic Bi2Fe4O9 phase. The maximum value of MD% (~0.12%) is enhanced by ~13 times in the composite than in the pure sample. Therefore, the improved MD coupling and symmetric switching of the MD loop of the composite make it a suitable candidate for low power consumption storage devices.

1. Introduction

Ceramic materials are in demand due to their growing use in energy harvesting technologies, including batteries, capacitors, and storage devices [1]. There are two types of ceramic materials, i.e., traditional and advanced. The advanced ceramic material plays a significant role in the sensor and storage devices due to its high piezoelectric and resistive properties. These materials include oxides, nitrates, and carbides [2]. In these ceramics, the unique ferroelectric, electrochemical, pyroelectric, and piezoelectric properties are often useful for multiferroic research. The multiferroic materials with the simultaneous occurrence of various ferroic orders such as ferro (electric/magnetic), antiferromagnetic (AFM), ferrotoridic, and ferroelastic play a significant role in developing new technological and device applications [3]. In the recent past, researchers are focused on device miniaturization, which satisfies the vast need to integrate the electric and magnetic properties in a material. There are a variety of coupling mechanisms between the electric and magnetic orders, but magnetoelectric (ME) coupling is crucial for future micro/nanoscale electronics, low-power memory devices, and spintronic devices [4]. The ME effect was initially studied in the Cr₂O₃ single-phase compound. After that, many materials such as DyMn₂O₅, TbMnO₃, and BiFeO₃ showed the ME coupling in its single-phase [5]. However, these materials restrict their practical suitability applications due to the weak coupling among the electric and magnetic order parameters and the transition temperature below the room temperature (RT). To avoid the above difficulties in the single-phase materials, many researchers have focused their study on designing the composite materials [6]. Usually, in composite, the electric and magnetic properties are intentionally improved by adding the required electric and magnetic phases. The induced ME coupling in the composite is the product property relation between the constituent phases. The relation between the magnetic and electric phases is written as [7]:

$$M{E}_{\mathrm{E}}=\frac{\mathrm{electric}}{\mathrm{mechanical}}\times \frac{\mathrm{mechanical}}{\mathrm{magnetic}}\mathrm{and}M{E}_{\mathrm{H}}=\frac{\mathrm{magnetic}}{\mathrm{mechanical}}\times \frac{\mathrm{mechanical}}{\mathrm{electric}}$$E1

The origin of ME coupling in the composite may be strain, charge, and exchange bias mediated. It depends upon the coupling interaction at the magnetic and electric phase interface.

The alternative approach to study the coupling among the magnetic and electric ordering is the magnetodielectric (MD) effect. The existence of ME coupling can indirectly address through the MD effect. This phenomenon is defined as the magnetic field-controlled dielectric properties and reversely electric field-induced magnetic permeability [8]. Materials having MD characteristics are rich in physical content to take further research and its practical utilization. Usually, the signature of the MD effect can be realized by observing the anomaly of magnetic/dielectric transition in the dielectric/magnetic properties. The MD effect can be experienced experimentally by measuring the capacitance at the different external magnetic fields. The microscopic source of the MD effect can be originated from the extrinsic and intrinsic mechanisms. It solely depends on the origin of the dielectric properties of the material. According to G. Catalan, the MD effect can arise without having the dielectric and magnetic coupling in the sample [9]. The extrinsic mechanism responsible for the origin of the MD effect is the magnetoresistance and Maxwell-Wagner effect of the sample. Similarly, the intrinsic source of the MD effect originated from the magnetic field-induced dipolar switching mechanism. Hence, the existence of an intrinsic MD effect in a material indicates the possible signal of ME coupling. The realization of ME coupling is restricted by the symmetry requirements. The MD materials are fascinating due to their multiple microscopic origins and simplicity for device application. Recently, the MD coupling has been used to characterize the magnetic multipole orders and quantum criticality [10]. Therefore, it is necessary to investigate the MD coupling and the improvement of dielectric properties with the applied magnetic field.

The Aurivillius compound is composed of the perovskite layer (A_n−1B_nO_3n + 1)²⁻ sandwich periodically between the (Bi₂O₂)²⁺ fluorite layer. Here, n represents the number of perovskite layers present in the compound. For n = 4, Aurivillius compound Bi₅Ti₃FeO₁₅ (BTFO) is explored theoretically using the first principle calculation and experimentally [11]. The BTFO compound exhibits the orthorhombic crystallographic structure with the A2₁am space group at RT. BTFO undergoes the structural transition at high temperature from ferroelectric A2₁am transform to paraelectric I4/mmm at 730°C [12]. The BTFO has dragged the wide attention of researchers due to its high ferroelectric and piezoelectric properties above the RT. The single-phase BTFO shows the weak MD coupling at RT due to the unavailability of strong magnetic ordering. So, the artificially mixing magnetic phases in the form of the composite may provide a potential path to improve both magnetic and MD coupling in the sample. The first chosen material is La_0.67Sr_0.33MnO₃ (LSMO) to make the composite with the BTFO compound. Due to its exciting properties, i.e., high ferromagnetic ordering temperature ~370 K, colossal magnetoresistance, and high carrier spin polarization [13]. The second compound of interest is the Bi₂Fe₄O₉ (BFO), which has a unique spin frustration due to the interaction among the Fe ions. BFO ceramic shows nearly RT multiferroic behavior due to the high AFM ordering temperatures of ~260 K [14]. Therefore, the above properties of both LSMO and BFO compounds may play a pivotal role in improving the magnetic as well as MD behavior of the composite.

In this work, we have examined the physical properties of the 0.5Bi₅Ti₃FeO₁₅-0.2La_0.67Sr_0.33MnO₃-0.3Bi₂Fe₄O₉ composite and compared it with the pure BTFO sample. The composite sample is synthesized by the sol–gel-modified technique and their dielectric, magnetic, and the source of MD effect are discussed. MD coupling in composite might be used as a potential candidate for MD device design.

2. Experimental

2.1 Synthesis of the composite samples

The ceramic composites (0.5Bi₅Ti₃FeO₁₅-0.2La_0.67Sr_0.33MnO₃-0.3Bi₂Fe₄O₉) were prepared by the sol–gel modified method. At first, BTFO, LSMO, and BFO samples were synthesized separately via a sol–gel auto combustion process. The chemical reagent used for the preparation of the BTFO sample were bismuth nitrate (Bi(NO₃)₃.5H₂O), iron nitrate (Fe(NO₃)₃.9H₂O), and titanium isopropoxide (TiC₁₂H₂₈O₄). The above chemicals were taken from Sigma-Aldrich with greater than 99.9% purity form. The deionized water was used to mix the nitrates. Bismuth nitrate and titanium isopropoxide were immiscible with the deionized water. The required drop of nitric acid was used to dissolve the chemicals and get the transparent white-colored solution. After that, add the iron nitrate to the above solution and heat it on the hot plate at 100°C. Then the desired ratio of ethylene glycol and citric acid (1:1.5) was added to the mixture. All the reagents are mixed completely and lead to the formation of the gel. The xerogel was dried on the hot plate overnight and crushed to form the homogenous powder. The resultant powder was pre-sintered in a tubular furnace at 600°C for 2 h. A similar method was used for the preparation of LSMO and BFO samples. Only the difference in the precursor materials and pre-sintered temperatures. The starting materials such as lanthanum nitrate (La(NO₃)₃.6H₂O), manganese nitrate (Mn(NO₃)₂.4H₂O), strontium nitrate (Sr(NO₃)₂) and bismuth nitrate, iron nitrate were used for the preparation of LSMO and BFO sample, respectively. The obtained xerogel powder was pre-sintered at 800°C for 4 h and 800°C for 2 h for the LSMO and BFO samples, respectively.

Finally, the composite (0.5Bi₅Ti₃FeO₁₅-0.2La_0.67Sr_0.33MnO₃-0.3Bi₂Fe₄O₉) was prepared by taking the desired ratio of as-synthesized BTFO, LSMO, and BFO powder. The proper weight percentage of 50% BTFO:20% LSMO:30% BFO (abbreviated as BLB523) was taken and mixed thoroughly with the help of agate mortar and pestle to get the homogeneous powder. The obtained powder was pressed to form the pellet and finally sintered at 900°C for 4 h.

2.2 Characterization

The phase identification of the pure cum composite samples was analyzed by using the X-ray diffraction (XRD) system with an ULTIMA-IV diffractometer of Cu source of radiation. The diffraction data were taken in the range of 20–60° with a slow scan rate of 3 degrees per minute. The surface morphology and elemental analysis were characterized through the scanning electron microscope (SEM) coupled with the energy dispersive X-ray spectrometer (EDAX). The size of the grains was estimated from the Image J Software. The samples magnetic properties were studied at room temperature (RT) using the vibrating sample magnetometer (VSM) with a maximum magnetic field of 15 kOe. For the electrical measurement samples were painted with high-quality silver paste to form an electrode. The RT frequency variation of dielectric permittivity at a constant magnetic field (0 to 1.3 T with a difference of 0.2 T) was studied through the impedance analyzer (Waynee Kerr 6500B model). The magnetic field variation of MD and magnetoloss was recorded by an impedance analyzer, which is assembled with the closed cycle refrigerator (CCR) system, KEPECO power supply, and the electromagnet (GMW 5034).

3. Results and discussion

3.1 Structural characterization by XRD

Figure 1(a) and (b) illustrate the XRD patterns of the pure BTFO and composite (BLB523) samples. The measured XRD data is examined through the Rietveld refinement procedure using the Fullprof software. The refinement result provides information related to the samples pure phase formation and structural parameters. For the pure BTFO sample, the single-phase refinement method is performed by considering the orthorhombic crystal structure (A2₁am space group). In contrast, the tri-phase method is incorporated in order to refine the whole XRD pattern of the composite. The orthorhombic (A2₁am) BTFO, rhombohedral (R-3c) LSMO, and orthorhombic (Pbam) BFO symmetry is provided as input sources during the composite refinement. Initially, the instrumental zero correction factor is refined in the refinement process, followed by the scale factor, cell parameters (a, b, and c), FWHM parameters (u, v, and w), background points, and atomic positions. The peak shape parameters and background points are fitted by providing the Pseudo-Voigt function and linear interpolation between the background points. After several refinement cycles, the theoretically simulated pattern is well matched with the experimental data points. Additionally, the lower value of χ², R_p, and R_wp also confirm the good fitting of the theoretical model with the observed data points. The extracted structural parameters and phase fractions are presented in Table 1. It is observed that the lattice parameters of the composite phase show a slight deviation from that of the pure phase. It signifies the generation of lattice strain at the BTFO, LSMO, and BFO domain interfaces. The other composites also report a similar kind of variation [15]. The proposed phase fraction of the composite is well consistent with the refinement data. Hence, the existence of BTFO, LSMO, and BFO phases in the composite assure the formation of the BLB523 composite.

Figure 1.

Rietveld refinement of the XRD patterns of (a) pure (BTFO) and (b) composite (BLB523) sample.

BTFO (pure)		BLB523 (composite)
Parameters		BTFO phase	LSMO phase	BFO phase
Crystal system	Orthorhombic	Orthorhombic	Rhombohedral	Orthorhombic
Space group	A21am	A21am	R-3c	Pbam
Lattice parameters (Å)	a = 5.4555(11)	a = 5.4537(9)	a = 5.5618(8)	a = 7.6813(9)
	b = 5.4467(11)	b = 5.4491(5)	b = 5.5618(8)	b = 8.5883(6)
	c = 41.2130(7)	c = 41.0190(4)	c = 13.600(6)	c = 5.8567(11)
Cell volume (Å^3)	1224.63(10)	1218.995(6)	364.33(7)	386.36(9)
Phase fraction	100	50.79	20.63	28.58
Rp (%)	2.20	10.4
Rwp (%)	2.25	9.65
χ^2	1.84	3.07
Crystallite size (nm)	41.76	51.35
Strain	10.2 × 10^−4	18.2 × 10^−4

Table 1.

Summary of the refined lattice parameters, crystallite size and strain of the BTFO and BLB523 composite.

The mean lattice strain and crystallite size of the pure cum composite samples have been extracted from the Williamson-Hall (W-H) plot method. The mathematical expression of the W-H method is

$$\beta cos\theta =\frac{K\lambda }{D}+\mathbf{4}\epsilon sin\theta$$E2

here $\theta$ denotes the Brrag’s angle, $\epsilon$is the lattice strain, $\lambda$ is the incident wavelength of X-ray, $K$ is the shape parameter (0.89 for spherical shape), D is the crystallite size in average, $\beta$ denotes the full-width half maxima of the diffraction peak [16]. The estimated crystallite size and strain values are listed in Table 1. It is observed that the composite exhibits more strain than the pure sample.

3.2 SEM study

The surface micrograph of sintered pure cum composite samples are shown in Figure 2(a) and (b). These images reveal the existence of grains with different sizes and orientations in the samples. The pure sample consists of well-structured plate-like grains of various sizes distributed uniformly on the sample surface. At the same time, the composite consists of a mixture of three phases (BTFO, LSMO, and BFO). As LSMO grains exist in the nanometer range, it is difficult to identify from the SEM image. The average grain size of the pure and composite sample (mixed grains) is found to be 1.44 and 0.54 μm, respectively, which is estimated from the Image J software. The EDAX analysis is incorporated to analyze the sample’s elemental composition, as shown in Figure 2(c) and (d). The EDAX spectrum indicates the constituent elemental peaks of the Bi, Ti, Fe, O and Bi, Ti, Fe, La, Sr., Mn, and O for pure and composite samples. This analysis confirms the presence of the required element in the samples.

Figure 2.

(a) and (b) Backscattered SEM images of sintered BTFO and BLB523 samples, respectively. (c) and (d) The EDAX spectra of the corresponding pure and composite sample.

3.3 Magnetic study

The magnetization (M) versus magnetic field (H) loop for pure BTFO and composite BLB523 samples are recorded at RT. Figure 3(a) and (b) display the linear and slightly non-linear M-H loop of pure cum composite samples. This linear behavior of the M-H loop indicates the paramagnetic (PM) behavior of the pure sample. With the addition of magnetic LSMO and BFO phase, the M-H loop slightly changes to the non-linear behavior with a small opening in the field range of ±1 kOe, as shown lower inset of Figure 3(b). This behavior signifies the weak ferromagnetic (FM) nature of composite. In composite BLB523, saturation magnetization is not achieved even in a high magnetic field of 15 kOe. It indicates the presence of canted spins in the composite. Since the composite sample consists of the three magnetic phases, i.e., PM BTFO, FM LSMO, and AFM BFO phases [17, 18]. The overall magnetic behavior of the composite shows the FM behavior. As the pure sample exhibit the paramagnetic behavior, with the addition of magnetic Mn ion (LSMO) and Fe ion (BFO) to the BTFO phase. The magnetic moment of the composite sample is enhanced. The different magnetic parameters such as maximum magnetization (M_max), coercive field (H_c), and remanent magnetization (M_r) are extracted from the fitting of M-H loop [19] and listed in Table 2. It is observed that the magnetic parameters (M_max, H_c, and M_r) increase by adding an extra magnetic phase to the pure sample. Since the maximum magnetization is an intrinsic property of the sample, which depends upon the spin configuration and spin–spin interaction between the magnetic ions. Whereas, the coercive field and remanent magnetization is affected by extrinsic factors such as particle morphology, domain structure, disorder, defects, etc. [20].

Figure 3.

Magnetic hysteresis loops (M-H) of (a) BTFO and (b) BLB523 at RT.

Sample	Mmax (emu/g)	Mr (emu/g)	Hc (Oe)	Mr/Ms
BTFO	0.07 ± 0.02	3.44 × 10^−4; ±6.12 × 10^−6	50 ± 8	0.005
BLB523	0.23 ± 0.06	35.74 × 10^−4; ±8.37 × 10^−6	145 ± 21	0.016

Table 2.

Magnetic parameters are estimated from the M-H hysteresis loop.

In the present discussion, the coercivity value of the BLB523 composite is increased to 145 Oe (nearly three times) than the pure sample. It could be due to the addition of manganite (LSMO) and ferrite (BFO) phase leading to the hindrance of domain interaction and resulting in the pinning effect in the composite. A similar trend of coercivity is also observed in many composites [21]. The enhanced magnetization in the composite sample is addressed due to adding extra magnetic ions, i.e., Mn and Fe ions of LSMO and BFO phase, respectively. Additionally, the enhanced magnetization is supplemented by inherent magnetization arising due to d-d, f-d, and f-f exchange interaction between the Fe-Fe, Fe-Mn, and Mn-Mn ions [22]. The squareness ratio is estimated from the ratio of remanent and saturation magnetization of the samples and is given in Table 2. Usually, the ratio of (M_r/M_s) ≥ 0.5 indicates the single-domain structure, whereas (M_r/M_s) < 0.5 signifies the multi-domain nature of the sample [20]. In the present composite, the squareness ratio lower than 0.5 exhibits the multi-domain nature of the sample.

3.4 Dielectric study

The frequency variation of dielectric permittivity (ε′) at different external magnetic fields displays indirect access to define the magnetoelectric coupling of the material. There are the various techniques to observe the magnetodielectric effect of the sample, such as (i) the relative change of capacitance/impedance with the application of an external magnetic field and (ii) the appearance of magnetic/dielectric transition temperature in the temperature variation of dielectric/magnetic studies. In the present pure cum composite system, we have preferred the first technique to analyze the MD effect. The RT frequency dependence dielectric permittivity at a fixed magnetic field (0 T to 1.3 T with a difference of 0.2 T) is illustrated in Figure 4(a) and (b). Both the sample shows the appreciable change in capacitance/dielectric under the application of field up to 1.3 T. A close view of the change in dielectric permittivity is plotted in the upper inset of the pure (BTFO) and composite (BLB523) samples. The reduction of ε′ with the change in a magnetic field signifies the presence of negative MD coupling in the sample. The appearance of the positive or negative sign of the MD effect depends on the neighboring spin pair correlation and the coupling constant [23]. The dielectric constant of both the samples decreases with the increase of frequency, suggesting the usual dielectric characteristics of the sample. The moderate change of dielectric constant under the different magnetic fields in the low-frequency regime is attributed to interfacial polarization i.e., Maxwell-Wagner polarization, space charge polarization, magnetoresistance, etc. [24]. Whereas, in the high-frequency region, the dielectric value decreases due to the intrinsic dipolar contribution and suppression of extrinsic effects. The maximum strength of the ε′ is found to be ~105 and 375 at 100 kHz for BTFO and BLB523 samples, respectively. It is observed that the strength of the ε′ increases nearly three times in the composite sample. The strength of ε′ is reduced towards the high-frequency side by the suppression of extrinsic effects. Hence, the frequency plays a vital role in observing the sample’s dielectric properties even in the presence of the magnetic field. To suppress the extrinsic contribution towards the dielectric and magnetodielectric properties of the sample. It is pivotal to study in the high-frequency region of ≥50 kHz. The aforementioned discussion gives a signature of the existence of MD coupling in the sample. The upcoming section has demonstrated a clear view of the field variation MD effect and its possible source of origin.

Figure 4.

The frequency dependence of dielectric permittivity at the different magnetic fields of 0 T to 1.3 T (a) pure BTFO and (b) composite BLB523.

3.5 Magnetic field-dependent MD analysis

To realize the influence of magnetic field on dielectric properties of the pure and composite samples, field variation of MD measurement is recorded at RT. The MD effect can be extracted experimentally by recording the field variation dielectric data. While for the magnetoloss (ML) effect, dielectric loss data is taken as a function of a magnetic field. Both the MD and ML percentage is estimated using the following mathematical expression [19]:

$$\mathbf{M}\mathbf{D}\left(\%\right)=\left[\frac{{\epsilon }^{\prime }\left(H,T\right)}{{\epsilon }^{\prime }\left(\mathbf{0},T\right)}-\mathbf{1}\right]\times \mathbf{100}$$E3

$$\mathbf{ML}\left(\%\right)=\left[\frac{tan\delta \left(H,T\right)}{tan\delta \left(\mathbf{0},T\right)}-\mathbf{1}\right]\times \mathbf{100}$$E4

here ${\epsilon }^{\prime }\left(H,T\right)$, ${\epsilon }^{\prime }\left(\mathbf{0},T\right)$, $tan\delta \left(H,T\right)$, and $tan\delta \left(\mathbf{0},T\right)$ are dielectric permittivity and loss with magnetic field and zero magnetic field, respectively. Figure 5(a)–(d) illustrates the magnetic field variation of MD% and ML% of pure cum composite samples at a constant frequency of 50 kHz. The chosen high frequency plays a vital role in exploring the extrinsic and intrinsic origin of the MD effect. The extrinsic origin arises due to the Maxwell-Wagner polarization and magnetoresistance of the sample. At the same time, the intrinsic contribution arises due to the dipolar polarization. To exclude the unwanted extrinsic contribution from the observed MD effect, the observed MD data is taken at a high-frequency region (50 kHz). The pure and composite samples show a completely different MD loop with the maximum field sweep of ±13 kOe. The BTFO pure sample shows the linear nature of the MD effect with field variation. It is because of the dominating contribution attributed by the space charge polarization. Interestingly, with the addition of the LSMO and BFO magnetic phase, the behavior of the MD hysteresis loop is improved. The composite sample exhibits the symmetric hysteresis loop in both positive and negative magnetic field sweeps. This MD loop is termed the inverted butterfly loop. The maximum strength of the MD% for the pure sample is ~0.01% at 13 kOe of field. With the addition of LSMO and BFO samples, the MD% of the composite sample increases to ~0.12%, which is nearly 12 times more than the pure sample. In composite, the change of MD% slope is significant around the ±8 kOe field. After that, the change of MD% tends to saturate towards the higher field of ±13 kOe. This may be due to the addition of magnetostrictive LSMO phase arising from the Mn ions spin reorientation, which makes a good mechanical coupling with the different phases. As a result, MD coupling increases up to a certain magnetic field after that, the value of magnetostriction becomes saturated with a further increase of the magnetic field. A similar kind of observation is also reported in another magnetostrictive compound [25]. According to the G. Catalan formalism, it is crucial to consider the ML effect for demonstrating the origin of the MD effect [9]. The composite sample shows the contrasting nature of ML% to that of MD%. The maximum strength of ML% (~1.08%) at 13 kOe for the pure sample is decreased to ~0.08% in the composite sample. It indicates a slight decrease in loss is observed in the composite sample. The microscopic source of the MD effect can be explained in this way: (i) the magnetostrictive LSMO phase generates the strain at the interface of the ferroelectric phase. This strain is transferred to the ferroelectric phase, which results in the capacitance of the sample [26]. (ii) the addition of the AFM BFO phase can enhance the magnetic moment due to the presence of canted spins. The non-collinear alignment of magnetic spin results in modifying the electric polarization or capacitance of the sample via inverse Dzyaloshinskii-Moriya interaction (IDM) [27]. This IDM interaction is the fundamental source behind the MD effect in the non-collinear spin structure. However, the exact source of MD coupling in the composite is still to be observed via different experimental and theoretical investigations. Hence, the symmetric switching MD hysteresis loop with good coupling strength (~0.12%) in the composite sample might be used in the charge storage devices.

Figure 5.

(a) and (b) Magnetic field variation of magnetodielectric (MD%) at a frequency of 50 kHz. (c) and (d) Magnetoloss (ML%) vs. H at 300 K for pure and composite samples.

4. Conclusion

In summary, the pure cum composite (0.5Bi₅Ti₃FeO₁₅-0.2La_0.67Sr_0.33MnO₃-0.3Bi₂Fe₄O₉) is successfully prepared by using the sol–gel and its modified technique. The XRD analysis confirmed the existence of single (A2₁am) and composite (A2₁am, R-3c, and Pbam) phases in the pure and composite samples, respectively. The SEM analysis has confirmed the presence of homogeneous and heterogeneous microstructure of pure and composite samples. The presence of constituent elements of different phases has been detected from the EDAX spectrum. The average grain size of the pure and mixed grains of the composite sample is found to be 1.44 and 0.54 μm, respectively. The addition of magnetic LSMO and BFO phases enhances the overall magnetic properties of the composite sample. The magnetic parameters M_s and H_c in the composite are enhanced by nearly three times than the parent BTFO. This is attributed to the inherent d-d, f-d, and f-f exchange interaction between the Fe-Fe, Fe-Mn, and Mn-Mn ions. The frequency dependence of the dielectric constant at a fixed magnetic field demonstrates a signature of the MD effect in the pure and composite samples. This observation encourages studying the MD effect in the pure cum composite sample. The field-induced maximum strength of the MD effect is about ~0.12% at 50 kHz observed in the composite sample. This MD effect can be the combined effect of strain magnetostrictive LSMO and the inverse Dzyaloshinskii-Moriya interaction generated by the non-collinear Fe ions in the AFM BFO phase. Hence, the present composite establishes a relation between the electric and magnetic order of the constituent phases and further study can explore possibilities in MD device applications.

Acknowledgments

All authors would like to acknowledge the Board of Research in Nuclear Science (Project No: 2012/37P/40/BRNS/2145), Mumbai, the UGC-DAE CSR Mumbai (Project No: CRS/2021-2022/03/585), and the Department of Science and Technology (Project No: SR/FTP/PS-187/2011), New Delhi for funding.

Conflict of interest

The authors declare no conflict of interest.