Abstract :
In this work, X-ray diffraction data taken on Bi1−xLaxFeO3 solid solutions are used to verify the following structural phase transitions: “polar rhombohedral–antipolar orthorhombic” at x ≈ 0.16 and “commensurate–incommensurate” within the orthorhombic phase at x ≈ 0.18 . In contrast, in the Bi1−xPrxFeO3 series, the polar rhombohedral phase transforms into an antipolar orthorhombic one at x ≥ 0.13 . The polar rhombohedral phase near the morphotropic phase boundary exhibits an isothermal transformation into an antipolar orthorhombic phase, though the transformation occurs much faster in the case of La-doped compounds. The incommensurate structural phase was not detected in Bi1−xPrxFeO3 solid solutions. The ternary structural phase diagram is constructed for (Bi,La,Pr)FeO3 systems. In addition, the polar rhombohedral phase exhibits a magnetic field-induced transition from the modulated antiferromagnetic state into a homogeneous weak ferromagnetic state whereas the antipolar phase is a weak ferromagnetic state in the absence of an external field.
