Multiferroic Properties And Loop Dynamics Scale Of Bismuth-containing Perovskite Film

This paper assumes that the magnetic unit Bi FeO3,YFeO₃ or BiFe_0.5Co_0.5O₃ inserted into layered perovskite ferroelectric Bi₄Ti₃O₁₂ matrix,in order to synthesis single-phase magnetoelectric multiferroic materials at room temperature.Layered perovskite Bi₄Ti₃O₁₂-nBiFeO₃（n = 0.5、1.0、1.5）、Bi₄Ti₃O₁₂-YFeO₃、Bi₄Ti₃O₁₂-BiFe_0.5Co_0.5O₃ thin films were deposited on Pt/Ti/SiO2/Si substrates by sol-gel method,and the room-temperature ferroelectric,dielectric,magnetic,magnetodielectric properties were discussed.To obtain electric domain structure and the polarization switching information of the films,the scaling behaviors of the dynamic hysteresis on Bi₄Ti₃O₁₂-nBiFeO₃（n = 0.5、1.0）、 Bi₄Ti₃O₁₂-YFeO₃ films were investigated.Main results and conclusions are as follows:At room temperature,the films have good ferroelectricity,and with the increasing of magnetic unit BiFeO₃ layers,the weak ferromagnetic properties of Bi₄Ti₃O₁₂-nBiFeO₃（n =0.5 、 1.0 、 1.5）thin films were enhanced as predicted.The room-temperature magnetodielectric effect was observed and the MDC of the Bi₄Ti₃O₁₂-BiFeO₃ films is up to3.5 % under 100 kHz and 0.45 T.Under high electric field and high frequency,the scaling relations of the Bi₄Ti₃O₁₂-nBiFeO₃ films is <A>∝f-0.05Eo1.26.The films were influenced less by electric field amplitude and frequency,compared with Bi₄Ti₃O₁₂-0.5BiFe O3 films.So the ferroelectric properties are more stable.The Bi₄Ti₃O₁₂-YFe O3 films exhibit the coexistence of ferroelectric and weak ferromagnetic properties with the remanent polarization 2Pr 53.62 μC/cm2 and the saturated magnetization Ms 0.50 emu/cm3 at room temperature.The conduction mechanism of the films from 10 to 300 kV/cm is dominated by Ohmic mechanism、space-charge-limited current（SCLC）、and trap filled-limit（TFL）current,respectively.The layered perovskite Bi₄Ti₃O₁₂-BiFe_0.5Co_0.5O₃ films of c axis orientation were prepared.The films exhibit the coexistence of ferroelectric and weak ferromagnetic properties with 2Pr 20 μC/cm2 and Ms 4.3 emu/cm3 at room temperature.The Ms value is much higher than the Ms 0.45 emu/cm3 of the Bi₄Ti₃O₁₂-BiFeO₃ films.The MDC of the films is 3.1 % under 0.45 T/100 kHz,and the MDC value is slightly lower than the MDC value3.5% of Bi₄Ti₃O₁₂-BiFeO₃ films.We think,Co ion partly replacing Fe ion,restrained the generation of Fe2+ ion in the Bi₄Ti₃O₁₂-BiFe_0.5Co_0.5O₃ films,thus Fe2+ and Fe3+ dipoles reduced.