Eur. Phys. J. B 73, 375-381 (2010)
https://doi.org/10.1140/epjb/e2010-00004-y

Structural and magnetic phases of Bi_1-xA_xFeO_3-δ (A = Sr, Pb) perovskites

¹ Scientific-Practical Material Research Center NAS Belarus, 220072 Minsk, Belarus
² Physical-Engineering Institute of Low Temperatures, 61103 Kharkov, Ukraine
³ Helmholtz-Zentrum-Berlin for Materials and Energy, 14109 Berlin, Germany
⁴ Laboratory for Neutron Scattering, Paul Scherrer Institute and ETH Zurich, Switzerland
⁵ Joint Institute for Nuclear Research, 141980 Dubna, Russia

Corresponding author: bushinsky@physics.by

Received: 19 June 2009
Revised: 25 November 2009
Published online: 15 January 2010

Abstract

The Bi_1-xA_xFeO_3-δ (A = Sr, Pb) systems have been studied using the X-ray, neutron powder diffraction and magnetization measurements in a magnetic field up to 14 T. It was found that around x ~ 0.06 the crystal symmetry changes from a rhombohedral (space group R3c) to pseudo-tetragonal. In the composition range 0.07 ≤ x ≤ 0.14 the phases with different symmetry of the unit cell coexist independent of synthesis conditions. The neutron powder diffraction shows that the iron ions have average oxidation state close to 3+. The magnetic structure for Bi_0.5Sr_0.5FeO_3-δ is found to be G-type antiferromagnetic with magnetic moment of about 3.8 μ_B/Fe³⁺. The weak ferromagnetic state due to magnetoelectric interactions was revealed in the lightly doped rhombohedrally distorted compositions. No evidence for a spontaneous magnetization was observed for the pseudo-tetragonal phases. These compositions show irreversible nonlinear magnetization vs. field behavior apparently due to small local deviations from the collinearity of the magnetic moments.