Magnetic, dielectric and impedance spectroscopy study of BiFeO3 multiferroic nanoceramics K. P. Bera, P. R. Mandal, T.K. Nath* Department of physics, Indian Institute of Technology Kharagpur, 721302, West Bengal, India *Corresponding author’s e-mail: firstname.lastname@example.org Abstract We report structural, magnetic, dielectric properties of BiFeO3nanoceramicssynthesized by sol-gel technique. DTA-TGA analysis indicates the signature of ferroelectric and magnetic phase transitions. The room temperature dielectric constant and tanδare found to be 615and 0.087, respectively. P-E loops exhibits ferroelectric nature. The magnetic measurements shows strong ferromagnetism. Keywords: Ferromagnetism, relaxation, dielectric behavior, ferroelectricity, impedance spectroscopy. space group R3c. The Rietveldrefinement confirms that the sample is well crystallized without having any impurity phases. The DTA curve (shown in Fig. 1) shows an exothermic peak at 325 OC and an endothermic peak at 805 OC corresponding to Neel and Cure temperature respectively. TG curve shows small weight lossof 0.26 % with increasing temperature from 270 to 540OC. The coexistence of Fe2+ and Fe3+(observed from XPS spectra as shown in the inset of Fig. 1) may be the plausible reason of enhance ferromagnetism. 1.2 10 O 30 C O 100 C O 200 C 8 0 14.1 13.8 -10 2.7 Fe 2p3/2 -20 3+ Fe 2.4 DTA 14.4 Intensity x 103(a.u) TG (%) 14.7 2+ Fe -30 -40 2.1 714 0 711 708 B.E.(eV) 300 600 T (oC) -50 900 1200 Fig.1: DTA-TG curve Novel chemical sol-gel route has been used to synthesizethe nanometric BFO powder using Bi(NO3)3, 5H2O and Fe(NO3)3,9H2O. The final powders arecalcined at 500 OC for 3 hours. The particle size are observed to be 50-70 nm obtaining from FESEM micrograph analysis. ExperimentalResults The Rietveld refinement of the XRD data has been performed using rhombohedral structure with 3 1.0 4 'x10 2 0.8 0 1 2 10 10 3 10 0.6 30 5 10 6 10 7 10 O C O 100 C 200 10 2.4 2 0.2 P (C/cm2) 1.8 4 10 f (Hz) 0.4 Z"X106(ohm) Multiferroic materials exhibit simultaneously the coexistence of ferroelectricity and ferromagnetism in same crystallographic phase. Due to the magnetoelectric coupling they have potential application in data storage device, spintronics, microelectronics etc. Among all perovskites (ABO3type) BiFeO3 (BFO) exhibits room temperature multiferroicity. Synthesis of pure BFO in bulk phases as well as in nanometric phase is challenging due to the unwanted appearance of Fe-rich impurity phases during synthesis.Careful synthesis, doping, and epitaxial thin film growth etc. help to overcome the high leakage current, suppressionof the superior FE polarization and superimpose of spiral spin modulation on G-type AFM ordering . 6 tan Introduction (a) 0.1 10 O C 3 5.0 kV/cm 10.0 kV/cm 12.5 kV/cm 15.0 kV/cm 4 10 10 f (Hz) 5 10 6 250 275 2.5 Hz -0.1 7 300 K 0.0 300 -0.2 1.2 10 325 -15 -10 -5 0 5 E (kV/cm) 10 15 350 O O O O O C C C C C 0.6 (b) 0.0 0.0 0.5 1.0 1.5 Z'X106(ohm) 2.0 2.5 Fig.2: (a) Frequency dependent ε' at different temperatures (Inset shows tanδ versus frequency at different T). (b) Nyquist plots at different T. (Inset shows room temperature P-E loops at 2.5 Hz) The high value (700 at 100 Hz) of low frequency ε' at room temperature is attributed to the Maxwell-Wagner type polarization. Impedance spectroscopy shows non Debye type relaxation behavior. The decrease of Z' with increase in temperature indicate the semiconductor like behavior of nanometric BFO. The activation energy (1.31 eV) has been calculated from the frequency corresponding to Z" maxima versus 1/T plot (not shown here) using Arrhenius law. The P-E loops (room temperature) indicate the ferroelectric behavior of the sample. The magnetic measurement reveals strong ferromagnetic nature of nanometric BFO. Reference . V. Goianet. al.J. Appl. Phys. C 110, 074112 (2011).