Magnetic and dielectric properties of Ca2+ doped Bi0.9La0.1FeO3 nanoparticles prepared by the sol-gel method

Abstract

Bi_{0.9<em>-x</em>}La_0.1Ca<em>_x</em>FeO₃(<em>x=</em>0.05~0.25) nanoparticles were synthesized by an improved sol-gel technique. With an increasing <em>x</em> value, the grain size exhibits an initial drop followed by a subsequent rise. The temperature has a strong effect on the morphology of samples. This implies that 700℃ is the optimal temperature for the growth of crystals in the samples. The magnetization increases with an increase in the concentration of Ca²⁺ions, and the doped crystals exhibit important features of anti-ferromagnetic spin ordering. The remanent magnetization (<em>M</em>_r) exhibits an initial reduction with a subsequent increase versus concentration (<em>x</em>) of Ca²⁺ ions, its minimal value corresponding to <em>x=</em>0.2. The substitution of Bi³⁺ions by Ca²⁺ ions results in the change of the Fe³⁺-O-Fe³⁺bond angle, accompanied by a distortion of the oxygen octahedra. With an increase in frequency, multiple Debye peaks appear in all samples, which indicate that the material possesses multiple-frequency energy absorption characteristics. Thus, the frequency-dielectric loss curve is characterized by the superposition of multiple Debye peaks.