Structural stability and magnetic properties of Bi_1-xLa(Pr) _xFeO₃ solid solutions

In this work, X-ray diffraction data taken on Bi_1-xLa _xFeO₃ solid solutions are used to verify the following structural phase transitions: "polar rhombohedralantipolar orthorhombic" at x≈0.16 and "commensurateincommensurate" within the orthorhombic phase at x≈0.18. In contrast, in the Bi _1-xPr_xFeO₃ 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 Bi_1-xPr_xFeO ₃ 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.