Structure And Magnetic Properties In La、Er Doped BiFeO₃Thin Films

Multiferroic materials that show ferroelectric, ferromagnetic and ferroelasticityin the same phase can produce properties that single-ferroic material does not have.We can design memory materials which is written by electric and read by magnetic,such as information storage, spintronic devices, optical devices and sensors. In recentyears, people have been looking for the materials that can show both ferroelectric andferromagnetic at room temperature, and has significant magneto-electric effects.BiFeO3(BFO) is the only one that exhibits both ferroelectricity and G-typeantiferromagnetism at room temperature. But compared with its excellent ferroelectricproperties, its magnetic properties are too weak to reach practical standard. Thepurpose of this paper is to improve magnetic of BFO by rare earth ions doped.In this paper, BFO thin films, Bi1-xLaxFeO3(x=0,0.05,0.1,0.15) thinfilm,Bi1-xErxFeO3(x=0,0.050.1,0.15) thin films have been prepared on Si (100)substrate via a simple spin-coating process. The main conclusions are as following:(1) BFO thin films: We determine the preheated temperature of BFO thin filmvia testing precursor powder by TG-DTA and IR. The preheated temperature is350℃.BFO thin films have been annealed at different temperatures (500℃,600℃,700℃).The XRD result shows that the thin film annealed at500℃is pure phase and filmquality is best. The SEM results show that the surface of the thin film annealed at500℃is most smooth. The structures and properties of the thin film annealed at500℃were studied via Raman、SEM、TEM、VSM. The VSM results reveal that BFOthin film showed weak magnetism.(2) Bi1-xErxFeO3thin films: Preheated temperature of films is350℃, and theannealed temperature of films is500℃. The structures and properties ofBi1-xLaxFeO3thin films were studied via XRD、Raman、SEM、TEM、XPS、VSM. XRD, TEM andRaman results show that Er successfully occupy the Bi site. When Er dopingconcentration is0.15, the structures sample transform from rhombohedral to orthorhombic. TEM results show that the Er evenly distributed in the BiFeO3. VSMresults show that the magnetization of Bi1-xErxFeO3gradually enhanced with theincrease of Er doping concentration. When x is0.1, the magnetization of thin filmincreased from1.8emu/cm2to9.7emu/cm2. When x is0.15, the magnetization of thinfilm reduced to4emu/cm2.(3) Bi1-xLaxFeO3thin films: Preheated temperature of films is350℃, and theannealed temperature of films is500℃. The structures and properties ofBi1-xLaxFeO3thin films were studied via XRD、Raman、SEM、TEM、XPS、VSM. XRD、TEM、Raman results reveal that La substitute Bi site. With the increase of La dopingconcentration, the lattice of the sample is distorted. TEM results show that the Laevenly distributed in the BiFeO3. VSM results show that the magnetization ofBi1-xLaxFeO3gradually enhanced with the increase of La doping concentration. Themagnetization of thin film increased to5emu/cm2from1.8emu/cm2.