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

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 magnetoelectricmore » coupling (ME) coefficient.« less
Authors:
; ; ;  [1] ;  [2] ; ;  [3] ;  [4] ;  [5]
  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)
Publication Date:
OSTI Identifier:
22399306
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 11; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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