Robust Antiferromagnetism and Structural Disorder in BixCa1-xFeO3 Perovskites

Wei-tin Chen, Anthony J. Williams, Luis Ortega-San-Martin, Ming Li, Derek C. Sinclair, Wuzong Zhou, J. Paul Attfield

Research output: Contribution to journalArticlepeer-review

Abstract

An investigation of Ca substitution in the multiferroic material BiFeO3 shows that a wide range of perovskites BixCa1-xFeO3 (0.4 <= x <= 1.0) can be prepared by sintering in air at 810-960 degrees C. 0.4 <= x < 0.8 samples are cubic Pm<(3)over bar>m, whereas x = 0.8 and 0.9 show a coexistence of the cubic and the rhombohedral R3c BiFeO3-type structure. Considerable disorder arising from Bi3+ lone-pair distortions is evidenced by synchrotron X-ray and neutron studies of the average structures of the cubic phases, and electron microscopy reveals commensurate and incommensurate local superstructures. The BixCa1-xFeO3 (0.4 <= x <= 1.0) materials show a remarkably robust antiferromagnetic order with T-N = 623-643 K and ordered moments of 3.6-4.1 mu(B). They are "leaky" dielectrics with relative permittivities of similar to 30-100 and bulk resistivities similar to 50-500 k Omega cm at room temperature. The activation energy for bulk conduction increases from 0.27 eV for x = 0.4 to 0.5 eV for x = 1, but with a discontinuity at the cubic-rhombohedral boundary. Further processing of the x = 0.8 and 0.9 compositions to reduce conductivity through control of oxygen content could lead to improved BiFeO3-based multiferroics.

Original languageEnglish
Pages (from-to)2085-2093
Number of pages9
JournalChemistry of Materials
Volume21
Issue number10
DOIs
Publication statusPublished - 26 May 2009

Keywords

  • MAGNETIC-PROPERTIES
  • ELECTRICAL-PROPERTIES
  • BIFEO3
  • SYSTEM
  • TEMPERATURE
  • CERAMICS
  • CRYSTAL
  • BIMNO3
  • BI1-XCAXMNO3
  • CHARGE

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