High pressure crystal and magnetic phase transitions in multiferroic Bi0.9La0.1FeO3

Christopher S. Knee, Matthew G. Tucker, Pascal Manuel, Shengzhen Cai, Johan Bielecki, Lars Börjesson, Sten G. Eriksson

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22 Scopus citations

Abstract

The crystal and magnetic structures of multiferroic Bi0.9La 0.1FeO3 have been studied using high resolution neutron powder diffraction in the pressure range 0-8 GPa. Two structural phase transitions are observed. The first, at ∼1 GPa, transforms the polar R3c structure to an antipolar PbZrO3-like √2ap × 2√2ap × 2ap perovskite superstructure; the second, at ∼5 GPa, results in a smaller, √2ap × √2ap × 2ap unit cell and a structure described with Ibmm (nonstandard setting of Imma) symmetry, in which the a -a-b0 octahedral tilt system is retained and the antipolar cation displacements lost. Accompanying the changes in the nuclear structure, the antiferromagnetic spin structure evolves from a cycloid, with a modulation length, λ ≈ 770 Å, to collinear arrangements with the moments aligned along the b-axis (Pbam) and the a-axis (Ibmm) of the orthorhombic unit cells. In comparison with BiFeO3 the transition from a rhombohedral to an orthorhombic structure is suppressed by ∼3 GPa, reflecting the dilution of the stereochemically active bismuth lone pair by lanthanum. A correlation between the cell contraction of Bi1-xLa xFeO3 (0.0 ≤ x ≤ 0.3) induced by chemical pressure and hydrostatic pressure on BiFeO3 is determined, with substitution of 1 mol % of La approximately equivalent to application of 0.05 GPa. Bi 0.9La0.1FeO3 is found to have a higher bulk modulus than BiFeO3.

Original languageEnglish
Pages (from-to)1180-1186
Number of pages7
JournalChemistry of Materials
Volume26
Issue number2
DOIs
StatePublished - Jan 28 2014
Externally publishedYes

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