Structure and magnetic properties of potassium doped bismuth ferrite

The influence of the potassium (K+) doping on the structure of multiferroic BiFeO3 and its relation with ferroelectric and magnetic properties was investigated for perovskites with composition Bi1−xKxFeO3 in the range 0⩽x⩽0.07. All the studied samples are described in R3c space group (No. 161). Typical cell parameters (BiFeO3) in hexagonal setting are ahex=5.5769(2) Å and chex=13.8531(2) Å with Z=6 formula units. The structure determination shows that as the K+ content increases, the average cations displacements decrease reducing the polar character of doped samples with respect to pure BiFeO3 and leading to a change from rhombohedral to a pseudo-cubic symmetry. A structural disorder is related to the substitution of K+, which results in strong diffuse scattering (DS) located at the bottom of the Bragg peaks. Magnetic measurements reveal that all the compounds remain antiferromagnetic at room temperature (RT) with almost no change in the transition temperature (Néel temperature TN).