Magnetodielectric properties of Cr3+ ions doped BaTiO3 multiferroic ceramic Amit Kumar, Sonu Kumar, Manoj Prajapat, and C. Prakash Citation: AIP Conference Proceedings 1665, 140008 (2015); doi: 10.1063/1.4918217 View online: http://dx.doi.org/10.1063/1.4918217 View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1665?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Fe modified BaTiO3: Influence of doping on ferroelectric property AIP Conf. Proc. 1665, 040018 (2015); 10.1063/1.4917631 Local geometric and electronic structures and origin of magnetism in Co-doped BaTiO3 multiferroics J. Appl. Phys. 117, 17D904 (2015); 10.1063/1.4907182 Ferromagnetic antiphase domain boundary in Mn-doped hexagonal BaTiO3 multiferroics Appl. Phys. Lett. 102, 242910 (2013); 10.1063/1.4811699 Enhancing multiferroic properties in solid solution of Bi 1- x Sr x FeO 3 - BaTiO 3 ceramics AIP Conf. Proc. 1536, 611 (2013); 10.1063/1.4810375 Influences of annealing temperature on structural characterization and magnetic properties of Mn-doped BaTiO3 ceramics J. Appl. Phys. 112, 013909 (2012); 10.1063/1.4733691
Magnetodielectric Properties of Cr3+ Ions Doped BaTiO3 Multiferroic Ceramic Amit Kumar1,*, Sonu Kumar2, Manoj Prajapat3 and C.Prakash3 2
1Departmenmt
of Physics, I.I.S.E.R. Bhopal-462066, India, Department of Applied Science, ABSS Institute of Technology, Meerut, India 3 Department of Physics, I.I.S.E.R. Bhopal-462066, India * E-mail:
[email protected]
Abstract. Single-Phase BaTiO3 (BTO) and Cr3+ ions doped BTO i.e. BaTi0.8Cr0.2O3 (BTCO) were prepared by solid state reaction of ceramics. The value of dielectric permittivity at room temperature (ε´RT ~1200 at 100 Hz) of BTO was found to be higher than BTCO (ε´RT ~1000), this type of behavior may be ascribed due to distortion in lattice parameters (c/a). Substitution of Cr3+ ions at the site of Ti4+ ions (d0) will create oxygen vacancies and induce O2-(p)–Cr3+(d) hybridization. Magnetic moment of BTCO was found to be ~ 0.02 emu/g at an applied magnetic field of 4 kOe. The value of the magnetocapacitance was observed ~3.3%, which may be a sign of magnetoelectric coupling in the Cr 3+ ions doped BTO multiferroic system. Keywords: Dielectrics; Ferroelectrics; Magnetic materials PACS: 77.55.fe, 75.60.Nt, 62.25.Mn.
INTRODUCTION Multiferroic materials possess simultaneous ferroelectric, ferromagnetic, or even ferroelectric ordering, and exhibit promising applications in memories, spintronics, and magnetoelectric sensor devices [1-3]. The combination of both ferromagnetic and ferroelectric materials in a singlephase material is expected to produce new properties such as magnetoelectric [4-8]. BaTiO3 (BTO) is one of the best known ferroelectric compounds that have been extensively studied [9,10]. BTO having the Perovskite structure with tetragonal symmetry at room temperature, possesses a relatively large dielectric constant (ε'). In addition, BTO ceramics have a strong piezoelectric property. Here, we have done systematic studies on the structural, magnetic, dielectric and magnetoelectric properties of Cr3+ ion doped BaTiO3 ceramics. . .
EXPERIMENTAL DETAIL Polycrystalline BTO ceramic and Cr3+ ions doped BTO i.e. BaTi0.8Cr0.2O3 (BTCO) were prepared using
analytical grade (99.99% purity) TiO2, BaCO3 and Cr2O3 powders. The components were weight as per stoichiometric ratios and wet mixed for 3 h in acetone medium and calcined at 1100 ºC for 2 h in alumina crucible. Then pellets were sintered at 1150 0 C for 2 h. Finally obtained pellets were coated with silver paste and used as electrodes for dielectric measurement. The X-ray diffraction patterns of the samples were recorded at room temperature using an X-ray powder diffractometer with Cu- K radiation (1.5418 Å) at scanning rate of 1°/min. Dielectric measurements were carried out using a LCR Meter at different frequencies (100-10000 Hz). The magnetic hysteresis loops were measured using a SQUID Magnetometer (MPMS system; Quantum design). The magnetocapacitance (MC) was observed using a high frequency LCR-meter supplied with magnetic dipoles.
RESULTS AND DISCUSSION Fig. 1 shows the XRD patterns of sintered pellets of BTO and BTCO. The BTO sample was identified as tetragonal phase (JCPDS file #: 89-1428). Compare with the lattice parameters (a=4.0045, c=4.0420), of
Solid State Physics AIP Conf. Proc. 1665, 140008-1–140008-3; doi: 10.1063/1.4918217 © 2015 AIP Publishing LLC 978-0-7354-1310-8/$30.00
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BTO, lattice parameters of BTCO (a=4.0005, c=4.0095) were found to decrease (distorted in cubic). This may be due to the smaller ionic radii of Cr3+ (0.62 Å) compared with Ti4+ (0.75 Å). XRD peaks of BTCO found to be shifted towards higher Bragg’s angle (inset of Fig.1).
was found to be lower than dielectric permittivity of pure BTO (ε´RT ~1200 at 100 Hz). This type of behavior may be ascribed due to distortion in lattice parameters (c/a).
Figure 3. (a) Variation of magnetization of Cr3+ ions doped BTO with magnetic field at room temperature
Figure 1. XRD patterns of sintered pellets of BTO and Cr 3+ ions doped BTO as well as inset of figure shows the shifting of peaks.
Figure 2. (a)Variation of dielectric permittivity with frequency (b) dielectric loss with frequency at room temperature.
Fig. 2(a) shows the variation of dielectric permittivity (ε´) and dielectric loss (tan δ) with frequency. The value of dielectric permittivity of BTCO at room temperature (ε´RT ~1000 at 100 Hz)
It is already apparent from the XRD patterns that the phase transformation of BTO from tetragonal to distorted cubic structure. Reduced dielectric constant of BTO has been explained by the non-ferroelectric grain boundary due to defects [11]. High values of dielectric constant at lower frequencies are explained on the basis of space charge polarization due to inhomogeneities present in the dielectric structure, viz., porosity in the system.
Figure 4. Variation of magnetocapacitance of Cr 3+ ions doped BTO with magnetic field at room temperature at 1 kHz.
Fig. 3 shows the variation of magnetization with magnetic field. The magnetization of BTCO was observed to be ~0.02 emu/g at an applied magnetic field of 4 kOe. However, at higher magnetic fields (10 kOe), the diamagnetic nature of BTO dominates. Substitution of Cr 3+ ions at the site of Ti4+ ions (d0)
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will create oxygen vacancies and induce O2-(p)– Cr3+(d) hybridization. The charge carriers may be involved in bonding which arbitrate the exchange interaction via oxygen vacancies among the local spins; resulting in ferromagnetism. Nature of ferromagnetism with Cr3+ ions doping in BTO can be explained on the basis of carrier arbitrate by Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions [12]. The variation of ε´ in the presence of magnetic field is called the magnetodielectic effect or magnetocapacitance. The magnetocapacitance (MC) can be defined as: MC(%) =
' ( H ) ' (0) ×100 ' (0)
3.3 % at an applied dc magnetic field of 8 kOe at room temperature (frequency = 1 kHz), which is a sign of magnetoelectric coupling in the system. Our modified; Ferroelectric (BTO) →Multiferroic (Cr3+ ions doped BTO) system may be useful for device application.
ACKNOWLEDGMENT I, Amit Kumar, gratefully acknowledge the financial assistance provided by Ministry of Human Resource Development (MHRD). I am also thankful to Prof. K.G. Suresh (I.I.T.Bombay) for encourage to me.
REFERENCES
(1)
where ε´(H) and ε´(0) denote the values of ε´ in the presence and absence of magnetic field (H), respectively. In the presence of magnetic field the magnetic domains in multiferroic material will be strained which will produce stress on ferroelectric domains and then ferroelectric domains generate electric field. As a result, the dielectric behavior will be modified. The value of the magnetocapacitance ~ 3.3 % at an applied dc magnetic field of 8 kOe at room temperature (frequency = 1 kHz) as shown in Fig. 4. A similar type of observation was earlier reported in (La, Lu) doped BiFeO3 [13] as well as in composite film of BiFeO3 with PVDF [14].
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
CONCLUSIONS
[13]
Cr3+ ions doped BTO shows the magnetization of ~0.02 emu/g at 4 kOe, although well known pure BTO is ferroelectric material. In addition, value of the magnetocapacitance of BTCO was observed ~
[14]
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