Local bonds anomalies and dynamics in bismuth ferrite

C.-W. Wang,G. Deng,C. M. Wu,J. W. Lin,J. G. Lin,J. S. Gardner,V. K. Peterson

doi:10.1063/1.4978637

Abstract

The temperature evolution of the chemical and magnetic sublattice of bismuth ferrite has been investigated by neutron scattering below room temperature. Although the bulk lattice structure performed as expected, anomalies were measured in the local Bi-Fe and Fe-O bond lengths around 205 K, distorting the Fe polyhedra. The intensity and width of magnetic Bragg reflections were observed not to monotonically decrease as the system cooled, with distinct anomalies at 205 K. Inelastic neutron scattering above and below the 205 K transition revealed no significant difference in the low energy acoustic phonon. These insights will underpin and stimulate more detailed work aimed at understanding further the bismuth ferrite ordering taking place around 205 K.

Highlights

The first synthesized, room temperature multiferroic material was bismuth ferrite (BiFeO3, BFO) in 1957.1 Later, Moreau et al identified the crystal structure of BFO to be rhombohedral with room temperature lattice constants a = 5.5876 Å, c = 13.867 Å, with a space group of R3c and two chemical formula units per unit cell.[2]
In 1982, Sosnowska et al used high resolution neutron diffraction to identify a spiral structure in BFO,[4] which was later reclassified as a cycloid spin structure with a large period of wavelength ∼ 620 Å.5
The G-type antiferromagnetic structure of BFO was determined without ambiguity in 1963,3 the electrical nature of BiFeO3 was studied by Teague et al in 1960, who confirmed a ferroelectric hysteresis loop (TC ∼ 1100 K) in the material.[6]

Summary

Introduction

G. Lin2,a 1Neutron Group, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan 2Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan 3Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organization, Kirrawee DC, NSW 2232, Australia (Presented 4 November 2016; received 23 September 2016; accepted 26 December 2016; published online 13 March 2017)

Results

Conclusion