Neutron diffraction study of the (BiFeO₃)_1−x(PbTiO₃)_xsolid solution: nanostructured multiferroic system

Abstract

Neutron diffraction studies performed on the solid solution of (BiFeO(3))(1-x)(PbTiO(3))(x) reveal a mixture of two nanoscale phases with different crystal structures: a rhombohedral BiFeO(3)-based phase and a tetragonal PbTiO3-based phase. The ratio of Fe(3)+ and Ti(4)+ ions in the two phases is practically constant; only the proportion of the phases changes. The magnetic moments in the BiFeO(3)-based phase, in contrast to BiFeO(3), deviate from the basal plane. The temperature evolutions of the spin components along the hexagonal axis and within the perpendicular plane are different, leading to a spin re-orientation transition. The antiferromagnetic order in the PbTiO(3)-based phase corresponds to a simple structure with the propagation vector (1/2, 1/2, 1/2). The temperature dependence of the antiferromagnetic moment in the tetragonal phase at x = 0.5 indicates a canted antiferromagnetic order and a net ferromagnetic moment. A strong magnetic coupling between the two constituting phases due to the nanoscale character of the phases and well-developed interface between nanoparticles has been observed. The system of (BiFeO(3))(1-x)(PbTiO(3))(x) demonstrates an interesting scenario, where the proximity effects in the unstable system play a crucial role in the appearance of the unusual magnetic properties.

Investigation of new magnetoelastic and magnetic transitions accompanied with magnetoelectric coupling in $\boldsymbol {{\rm 0.1BiFeO_{3}{{\rm \mbox{--}}}0.9Sr(Fe_{0.5}Nb_{0.5})O_{3}}}$ multiferroic

“…Present study reveal that, introduction of 10% BiFeO 3 in Sr(Fe 0.5 Nb 0.5 )O 3 further enhances the ferromagnetic character. As shown in figure 1(a), the temperature dependence of dc magnetization M(T) of 0.1BF-0.9SFN ceramic has the lower temperature magnetic anomaly around ≈42 K. If we ignore the second magnetic anomaly in M(T) at 130 K, the shape of the M(T) plot is similar to that reported by Golosovsky et al [33] for the tetragonal (P4mm) phase of 0.5BiFeO 3 -0.5PbTiO 3 ceramic. They have reported a magnetic transition around 23 K which is accompanied by the distortion in crystal lattice as evidenced by appearance of anomaly in lattice parameter at the magnetic transition.…”

Zinc blende and wurtzite CoO polymorph nanoparticles: Rational synthesis and commensurate and incommensurate magnetic order

“…Another possible source for the "rounding" of the phase transition could be a mutual interaction of wurtzite and zinc blende nanoparticles with different magnetic orders due to a well-developed interface between them. For example, magnetic proximity effects [30,44,45] between ZB-CoO, with a higher Néel temperature, and W-CoO could induce a magnetic order in the W-CoO. However, our neutron diffraction experiments with single phase wurtzite nanoparticles showed that although the diffraction signal was too weak to perform any quantitative calculations, the long-range magnetic order was unambiguously observed.…”

“…This indicates a strong anisotropic shape of the nanoparticles. The non-monotonic dependence of the peak broadening implies an "anisotropic size-effect", which is characteristic for diffraction of nanoparticles, whose shape cannot be well approximated by a sphere [29,30]. In this case, the "apparent size", i.e.…”

A novel perovskite oxide chemically designed to show multiferroic phase boundary with room-temperature magnetoelectricity

“…The same composition 0.7BiFeO 3 –0.3PbTiO 3 has been claimed to be a mixture of tetragonal P 4 mm and either rhombohedral R 3 c (ref. 44 ) or monoclinic Cc (ref. 35 ) structures.…”