Dielectric anomalies due to grain boundary conduction in chemically substituted BiFeO{sub 3}

Journal Article · Sat Mar 21 00:00:00 EDT 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4915110· OSTI ID:22399306

Kumari, Shalini; Ortega, N.; Pavunny, S. P.; Katiyar, Ram S. ^[1]; Kumar, A. ^[2]; Hubbard, J. W.; Rinaldi, C. ^[3]; Srinivasan, G. ^[4]; Scott, J. F. ^[5]

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1. Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931-3334 (United States)
2. CSIR-National Physical Laboratory, New Delhi (India)
3. Department of Chemical Engineering and Institute for Functional Nanomaterials, University of Puerto Rico, Mayagüez, Puerto Rico 00681 (United States)
4. Physics Department, Oakland University, Rochester, Michigan 48309-4401 (United States)
5. Cavendish Laboratory, Department of Physics, Cambridge University, Cambridge CB3 0HE (United Kingdom)

We describe systematic studies on Nd and Mn co-doped BiFeO{sub 3}, i.e., (Bi{sub 0.95}Nd{sub 0.05})(Fe{sub 0.97}Mn{sub 0.03})O{sub 3} (BNFM) polycrystalline electroceramics. Raman spectra and X-ray diffraction patterns revealed the formation of rhombohedral crystal structure at room temperature, and ruled out structural changes in BiFeO{sub 3} (BFO) after low percentage chemical substitution. Strong dielectric dispersion and a sharp anomaly around 620 K observed near the Néel temperature (T{sub N} ∼ 643 K of BFO) support strong magneto-dielectric coupling, verified by the exothermic peak in differential thermal data. Impedance spectroscopy disclosed the appearance of grain boundary contributions in the dielectric data in the region, and their disappearance just near the Néel temperature suggests magnetically active grain boundaries. The resistive grain boundary components of the BNFM are mainly responsible for magneto-dielectric coupling. Capacitive grain boundaries are not observed in the modulus spectra and the dielectric behavior deviates from the ideal Debye-type. The ac conduction studies illustrate short-range order with ionic translations assisted by both large and small polaron hopping. Magnetic studies indicate that the weak antiferromagnetic phase of BNFM ceramics is dominated by a strong paramagnetic response (unsaturated magnetization even at applied magnetic field of 7 T). The bulk BNFM sample shows a good in-plane magnetoelectric coupling (ME) coefficient.

• OSTI ID: 22399306
• Journal Information: Journal of Applied Physics, Vol. 117, Issue 11; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANTIFERROMAGNETISM
BISMUTH COMPOUNDS
CERAMICS
COUPLING
DIELECTRIC MATERIALS
DOPED MATERIALS
GRAIN BOUNDARIES
IMPEDANCE
IRON OXIDES
MAGNETIC FIELDS
MAGNETIZATION
MANGANESE COMPOUNDS
NEODYMIUM COMPOUNDS
PARAMAGNETISM
POLYCRYSTALS
RAMAN SPECTRA
TEMPERATURE RANGE 0273-0400 K
TRIGONAL LATTICES
X-RAY DIFFRACTION