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The structural origin of composition-driven magnetic transformation in BiFeO3-based multiferroics

Authors: U. Khomchanka, D.V. Karpinsky; S.V.Dubkov; M.V. Silibin; J.A. Paixão

Ref.: The 37th International Symposium on Dynamical Properties of Solids, DyProSo-2019 (2019)

Abstract: Having been considered as materials of exceptional technological importance, magnetoelectric multiferroics continue to attract tremendous research interest. While the steady progress achieved in this field over the past decades has made our understanding of the underlying physics substantially exhaustive and deep, some topics still remain to be debated. In particular, the reasons behind the composition-driven instability of the cycloidal antiferromagnetic order in a classical room temperature multiferroic, BiFeO3, are not fully understood yet. Herein, we present experimental evidence indicating that the evolution of the magnetic state in chemically-substituted bismuth ferrites is determined by the competition between the polarization- and oxygen octahedra rotation-related components of the Dzyaloshinskii–Moriya interaction. Taking into account that the Bi1−xCaxFe1−xTixO3 and Bi1−xBaxFe1−xTixO3 perovskites exhibit totally different compositional evolution of the magnetic behavior (contrary to the Ba/Ti doping, the Ca/Ti substitution stabilizes a weak ferromagnetic state in the polar phase), we use the neutron diffraction technique to compare the crystal structures of these materials and explore how the variation in the magnetic properties correlates with the parameters describing structural distortions. Both the Ca/Ti and Ba/Ti substitutions are proven to diminish the polar ionic displacements. The resulting effect of the chemical modification on the magnetic structure is shown to be largely dependent on the magnitude of the oxygen octahedra tilting.