Intrinsic nature of the magnetization enhancement in heterovalently doped Bi_1-xA_xFeO₃ (A = Ca, Sr, Pb, Ba) multiferroics

The mechanism of the formation of heterovalent-substitution-induced defects as well as their influence on the magnetic properties of BiFeO ₃-based multiferroics has been studied. It has been shown that heterovalent A²⁺ substitution results in the formation of oxygen vacancies in the host lattices of both antiferromagnetic and weak ferromagnetic Bi_1-xA_xFeO₃ (A = Ca, Sr, Pb, Ba; x = 0.2, 0.3) compounds, thus indicating the intrinsic (i.e. not related to defects themselves) mechanism of doping-induced enhancement of magnetization. A correlation between the ionic radius of the substituting element and the value of the spontaneous magnetization of the corresponding solid solution has been found. The experimental results suggest that A-site substitution with the biggest ionic radius ions effectively suppresses the spiral spin configuration of antiferromagnetic BiFeO₃.