Effect of alkaline earth metal doping on thermal, optical, magnetic and dielectric properties of BiFeO3 nanoparticles

Substrate-free pure-phase BiFeO3 (BFO) nanoparticles doped with alkaline earth metals (Ba, Sr and Ca) have been synthesized by a sol-gel route and their thermal, optical, dielectric and magnetic properties are discussed. The characteristic structural phase transitions of BFO nanoparticles are found to occur at much lower temperatures. A reduction of the Neel temperature has been observed in the doped samples in comparison with the pristine one, whereas the band gap shows a reverse trend. Iron was found to be only in the Fe3+ valence state in all the doped samples. Magnetoelectric coupling is seen in our samples. Weak ferromagnetism is observed at room temperature in all of the doped and undoped BFO nanoparticles with the largest value of coercive field ~1.78 kOe and saturation magnetization ~2.38 emu g-1 for Ba and Ca doped BFO nanoparticles, respectively.