Crystal-structure and magnetic phase transformations in solid solutions of BiFeO3-AFe0.5Nb0.5O3 (A = Ca, Sr, Ba, Pb)

Abstract

Solid solutions of Bi1 − x A x (Fe1 − x/2Nb x/2)O3, where A = Ca, Ba, and Pb, are obtained and their crystal structure and magnetic properties are investigated. It is shown that for A = Ca and x ≈ 0.15, the symmetry of the unit cell changes from rhombohedral (space group R3c) to orthorhombic (Pbnm). The transformation leads to the emergence of spontaneous magnetization due to the Dzyaloshinskii-Moriya interaction. Solid solutions with A = Pb remain rhombohedral up to a concentration of x = 0.3. Spontaneous magnetization sharply increases in the compound with x ≈ 1 at low temperatures and is due to the formation of the spin-glass component.