Preparation And Magnetoeletric Properties Of Multiferroic Bi_0.85La_0.15Fe_0.95Mn_0.05O₃ Multi-layer Films

Because of the combination of ferroelectric,ferromagnetic and megnetoelectric(ME)characteristics,multiferroic materials can be potential candidates in wide fields such as sensors,memory and microwave devices.BiFeO3 is a research focus due to its high Curie temperature(TC=1103K)and Neel temperature(TN=643K).However,a large leakage current and weak ferromagnetic property limits its application.In order to improve the ferroelectric and ferromagnetic properties of La,Mn co-doped Bi0.85La0.15Fe0.95Mn0.05O3(BLFMO)film,the methods of introducing buffer layer and growing epitaxial films were employed in this paper.The BLFMO film was prepared on Si substrates by sol-gel method.In order to illuminate the effect of bottom electrodes on the microstructures and properties of BLFMO film,the BLFMO films were prepared with(LaNiO3(LNO))and(La0.67Sr0.33MnO3(LSMO))as bottom electrodes,respectively.The results show that the film exhibits good ferroelectric property(Pr=15.69?C/cm2),however,the hysteresis loop was not observed when LNO bottom was used as bottom electrode.The BLFMO film showed higher ferromagnetic property when LSMO was used as bottom electrode and the saturation magnetization increased to 28.4emu/cm3,but the hysteresis loop was not observed.Highly c-axis oriented BLFMO epitaxial film and LNO/BLFMO/LNO,LSMO/BLFMO/LSMO trilayer films were prepared on single crystal LaAlO3(001)substrates using layer by layer heat treatment process in order to improve their ferroelectric and ferromagnetic properties.The trilayer films present a good epitaxial characteristic by the results of X-ray diffraction and transmission electron micrographs.And then the ferromagnetic and ferroelectric performance of the films was tested.The results show that LSMO/BLFMO/LSMO trilayer epitaxial films display a high saturation magnetization(Ms=585.9emu/cm3),which is two orders of magnitude increase compared to LNO/BLFMO/LNO trilayer epitaxial films.And a higher remnant polarization(Pr=50.61?c/cm2)was found in BLFMO/LSMO epitaxial films as well.The leakage current of BLFMO/LSMO epitaxial film reduced to10-5A/cm2 at electric field of 250kV/cm,which reduced an order of magnitude compared with the leakage current of BLFMO/LNO epitaxial film.