Preparation And Characteristics Of The PVDF/LCSMO Heterojunction

The perovskite multiferroics and magnetoelectrics composite materials are always popular in the field of material and physics.Because it belongs to the strong relationship which owns profound physicalproperties,it can be applied in high density Dynamic Random Access Memory?DRAM?,Non-volatile memory?FeRAM?,optical waveguide,pyroelectric sensors,MEMS coupler,etc.However,traditional ferroelectroics has annoyed by some obstacles such as materials need to be synthesized in high temperatures which leads to the difficulty in combining and integrating with the current silicon technology as well as the size of the device is close to the quantum limit,etc.Organic ferroelectric polymer attracts interests due to its low cost,easy fabrication and excellent ferroelectrics.In this paper,The author proposed a composite material combined organic ferroelectric polymer and perovskite magnetic oxide.To turn the magnetoelectric application into the reality,takes the advantage of its ability in controlling the anisotropy of the magnetism by electric polarization of organic ferroelectric material.Hopefully,The author's achievements will give new idea on this field so that people can learn more about the physical intension.This paper is divided into three parts,background and the fabrication of the material,the test of the heterojunction structure,and the analysis of the results and the mechanism.The chapter one is the introduction of the traditional perovskite multiferroic materials,including the structure and the origin of the perovskite.Additionally,the magnetoelecric material and its mechanism is covered.In the last part in this chapter,several ways of fabricating films in nano size are introduced.The chapter two gives the detailed way on how the organic ferroelectric polymer P?VDF-TrFE?film.The XRD patterns of the film in different thicknesses show the films are well crystallined.Along with this,the films can form only ? phase which possesses spontaneous polarization.The hysteresis loop shows the property can sustain even the thickness goes extremely thin.In chapter three,The author first gave out his work on the pre-fabrication of the SrTiO₃?STO?substrate which was confirmed by the Atomic Force Microscope?AFM?.He successfully grew theperovskite magnetic oxide LCSMO on the single phase STO substrate by using the pulse laser deposition system?PLD?.According to the XRD patterns,the films are in epitaxial growth.The results of the magnetic moment and the magnetic hysteresis loop in changing temperature show that the property of film is close to the bulk materials'.The room temperature phase transition was observed in the resistance-temperature curves.Furthermore,transition test data of Hall voltage shows that LCSMO will behave as anomalous Hall Effect in weak external magnetic field around RT,while it will disappear as the temperature going up.Finally,we developed a capacitor structure,in which the P?VDF-TrFE?film was used as dielectric layer.This device uses the ferroelectric polarization reversal to modulate the resistance behavior,which proves the effective modulation on the magnetic oxides by ferroelectric property of the organic ferroelectric polymer.