Stabilization of dielectric anomaly near the magnetic phase transition in Ca2+ doped BiFeO3 multifunctional ceramics

Abstract

Stabilization of a prominent peak in the variation of dielectric constant in Ca2+ doped BiFeO3 ceramics near the antiferromagnetic to paramagnetic phase transition is reported. Temperature dependent dielectric data also shows perceptible frequency dispersion starting from temperatures well below the Neel temperature. This observation has been explained in terms of “skin effect”. Clear signature of magneto-electric coupling is shown using the P–E loops measurement of magnetically poled samples. The presence of magneto-electric coupling is explained in terms of the modulation of canted spin structure. Using Rietveld refinement of X-ray and neutron data, it is shown that the rhombohedral distortion decreases with increasing Ca2+ content. Analysis of SQUID–VSM magnetic hysteresis data proves the occurrence of structure induced anti-ferromagnetic to weak ferromagnetic transition. Significance of these observations for future applications of divalent doped BiFeO3 ceramics is also discussed.