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Title: Giant room-temperature magnetodielectric coupling in spark plasma sintered brownmillerite ceramics

The dielectric, magnetic, and magnetodielectric properties of Ca{sub 2}FeAO{sub 5+δ} (A = Al, Ga) ceramics were investigated together with their crystal structures. Rietveld refinement of the X-ray diffraction data indicated that the space group of the Ca{sub 2}FeAlO{sub 5+δ} ceramic was Ibm2, whereas that of the Ca{sub 2}FeGaO{sub 5+δ} ceramic was Pcmn. Dielectric relaxation above room temperature, originating from the Maxwell–Wagner effect and polaronic hole hopping between Fe{sup 3+} and Fe{sup 4+} ions, was observed in both ceramics. Weak ferrimagnetic behavior was identified from the magnetic-field-dependent magnetization in these ceramics, which was attributed to the non-cancelled spins of the antiferromagnetic-ordered Fe{sup 3+} and Fe{sup 4+} ions. An intrinsic, giant, room-temperature magnetodielectric coefficient of up to −23.3% was achieved in the Ca{sub 2}FeAlO{sub 5+δ} ceramic at 50 MHz, which was attributed to the suppression of charge fluctuations of Fe{sup 3+} and Fe{sup 4+} ions in the magnetic field.
Authors:
; ; ; ; ;  [1]
  1. Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)
Publication Date:
OSTI Identifier:
22402422
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 22; Other Information: (c) 2014 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; ALUMINIUM OXIDES; ANTIFERROMAGNETISM; CALCIUM COMPOUNDS; CERAMICS; CRYSTAL STRUCTURE; GALLIUM OXIDES; HOLES; IRON COMPOUNDS; IRON IONS; MAGNETIC FIELDS; MAGNETIZATION; RELAXATION; TEMPERATURE RANGE 0273-0400 K; X-RAY DIFFRACTION