Preparation And Magneto-electricity Properties Of BNTM-LSMO Multiferroic Composite Thin Films

Multiferroic materials have been formally defined as materials that exhibit two or more primary ferroic order parameter simultaneously. Because they have a variety of basic ferroic orders, and these ferroic orders can produce coupling effect. Magnetoelectric is an effect that magnetic polarization can be tuned by an applied electric field, meanwhile the external magnetic field can also induce polarization. For these reasons, multiferroic materials are widely used in the new generation of sensors, information storage devices and spin electronic devices. So far, it has became a hot research field in functional materials.In this paper, the Bi3.15Nd0.85(Ti2.99Mn0.01)O12(BNTM) ferroelectric thin films were choosed as the study object. Firstly, the classification and application prospect of multiferroic materials and the main existing problems of multiferroic materials were briefly introduced. Then, we researched the effects of Bi3.15Nd0.85(Ti2.99Mn0.01)O12(BNTM) ferroelectric thin films annealed at different temperatures and the effects on microstructure and magnetoelectric properties of Bi3.15Nd0.85(Ti2.99Mn0.01)O12-La0.7Sr0.3MnO3(BNTM-LSMO) multiferroic composite thin films which deposited with different sequences. The main contents and results of this work are summarized as follows:1. The BNTM ferroelectric thin films were fabricated on Pt/Ti/SiO2/Si substrates by Sol-Gel method at deferent annealing temperatures. The effects of annealing temperature on the microstructure and electrical properties of BNTM were investigated. The results indicated that: the BNTM ferroelectric thin films show best crystallization, remnant polarization, leakage and dielectric properties with annealing temperature at 750 oC.2. We fabricated BNTM ferroelectric thin films and LSMO ferromagnetic thin films on Pt/Ti/SiO2/Si substrates by pulsed laser deposition(PLD) method. We found a good experiment parameter through repeated experiments exploration. The research results indicated that the single-phase BNTM ferroelectric thin films have good crystallization, compact structure and good ferroelectric properties grew in this parameter; The LSMO ferromagnetic thin films also have good crystallization, compact structure and good result in magnetic properties.3. On the basis of the above work, we deposited deferent sequences of BNTM/LSMO/ Pt/Ti/SiO2/Si(BLP) and LSMO/BNTM/ Pt/Ti/SiO2/Si(LBP) composite thin films based on ferroelectric Bi3.15Nd0.85-(Ti2.99Mn0.01)O12(BNTM) and ferromagnetic La0.7Sr0.3MnO3(LSMO) on Pt/Ti/SiO2/Si substrates by pulsed laser deposition(PLD) method. By characterizing the properties of multiferroic composite thin films, we found that these 2-2 type multiferroic composite thin films have good ferroelectric and magnetic properties, as well as small leakage current at room temperature. However, we found that(BLP) composite thin films performed better than(LBP) composite thin films. These findings suggest that the deposited sequence has a notable effect on the ferroelectric and magnetic properties as well as leakage current.