Synthesis And Properties Of LuFeO₃Multiferroic Materials

Multiferroic have became one hotspots of emerging disciplines spintronics in recent years, In particular, the magnetoelectric coupling mechanism have received much attention among scientists who are in the field of highly correlated electron systems. In this work, we select LuFeO3material as the object, and report it in four parts, such as ceramics of LuFeO3synthesis by solid state reaction, films of LuFeO3prepared by L-MBE, doped films of LuFeO3prepared by Sol-gel method and compound films (LuFeO3-MgFe2O4). The innovative results are showed here:1. Preparation and properties of LuFeO3ceramics.o The optical band gap of orthoferrites LuFeO3was2.78eV which was determined by spectroscopic ellipsometry. The magnetic ordering temperature is considered to be620K.The crystallographic structure of the ceramic was determined by X-ray diffraction and Raman scattering. Both the measurement indicates distorted orthorhombic perovskite structure with space group Pbnm. We obtain the optical band gap of LuFeO3by Kramers-Kronig and Tauc relation,2.78eV and2.76eV by spectroscopic ellipsometry. Mainly mechanism of LuFeO3ceramics for the bandgap, possibly arising from the electronic transitions between the majority channel Fe3d to O2p (t1g (∏) to t2g) charge transfer excitation, is studied using diffuse reflectance spectroscopy. The field cooled (FC) and zero filed cooled (ZFC) magnetization-temperature curves of the ceramic indicates it is an antiferromagnetic (AFM) and the Neel temperature is620K, which is in accordance with other research group.2. LuFeO3films are successfully prepared on Silicon wafer, conductive oxide and single crystalline substrates by L-MBE system. We Study the optical properties of LuFeO3film on Si (100) substrate, and the electrical properties of the film grown on LaNiO3/Si (100) substrate.The substrate temperature and gas pressure are very important in L-MBE system, the film on silicon with substrate temperature of800℃and oxygen pressure of lPa showed the optical structure and microtopography. We obtained the OBG of the film also by SE; it is3.0eV, which is higher than the ceramic. The conductive oxide LaNiO3used as bottom electrode, the remnant polarization of LFO films is about1.21μC/cm2, which is higher than the ferroelectric properties of LuFeO3ceramics.3. The thin films of Lu1-xBixFeO3(LBFOx,0≤x≤0.10) and MgFe2O4were prepared on LaNiO3coating silicon substrates by sol-gel method. The butterfly loops of LBFOx imply the typical characteristics of ferroelectric materials. The influence of annealing temperature on the magnetic properities of MgFe2O4thin films is studied at room temperature.Structural and morphological characterization of the LBFOx thin films was investigated by X-ray diffraction and atomic force microscopy, respectively. The remnant polarization of Bi-doped LuFeO3thin film at room temperature reached to3.1and3.6μC/cm2for x=0.05and0.10at the electric field of700kV/cm, respectively. The ferroelectric polarization measurements indicate that the potential role of Bi doping in increasing the value of the polarization of LuFeO3film, and the mechanisms for the U shaped frequency loss tangent curves was discussed. Magnesium ferrite thin films were directly fabricated on Silicon substrate by Sol-gel method. The specific saturation magnetization (Ms) values of MgFe2O4(annealed at700,800and900℃) are30.3,61.0, and134.7emu/cm3, respectively.4. Preparation and magnetic properties of LuFeO3-MgFe2O4(LFO-MFO) compound filmsThe target of MgFe2O4was synthesized by both solid state reacation and liquid phase reaction method. High quality MFO thin films with c-preferred were successfully fabricated on silicon substrates by L-MBE. LFO-MFO compound films are fabricated on Si (100), STO (100), A12O3(006) and MgO (100) also by L-MBE system. The magnetic hysteresis loops indicate exceptionally high coercivity and saturation.