Weak ferromagnetism in BiFeO3-based multiferroics

Abstract

The magnetic properties of the Bi1 − x Ln x FeO3 (Ln is a rare-earth ion), Bi1 − x A x FeO3 − x/2 (A is an alkali earth ion), and BiFe1 − x Ti x O3 + δ solid solutions in magnetic fields up to 14 T have been studied. The concentration ranges of the existence of the ferroelectric phase described by the space group R3c have been determined. It is shown that the substitution of the rare-earth ions for the Bi3+ ions leads to a sharp decrease in the critical fields inducing the metamagnetic transition from a modulated antiferromagnetic state to a weakly ferromagnetic one; however, the modulated structure in the concentration range of the R3c phase is mainly retained. The substitution of the alkali earth ions (x ∼ 0.1) for the bismuth ions leads to the total destruction of the modulated structure and to the implementation of the weakly ferromagnetic state within the R3c phase. A homogeneous weakly ferromagnetic state has been revealed when the Ti4+ ions (x = 0.1) are substituted for the Fe3+ ions in the ferroelectric R3c phase.