Preparation And Characterization Of Perovskite Manganites Thin Films By Chemical Solution Deposition

Perovskite manganites with a chemical formula of La_1-xA_xMnO₃（A is an alkalineearth element or alkaline element） exhibit various properties such as colossalmagnetoresistance （CMR） effect, Jahn-Teller Distortion, the charge orbital ordering,phase separation and metal-insulator transition, which show promising applications inmagnetic field sensors, hard disk read heads, and memory cells. CMR is due to thedouble exchange （DE） effects following a ferromagnetic coupling between Mn³⁺andMn⁴⁺ions. As a result, the tuning for the ratios of Mn³⁺/Mn⁴⁺becomes especiallynecessary in synthetic chemistry. In a number of doping manganites, the divalentelement dopants are studied. Accordingly, the studies of monovalent element dopingwhich may greatly change the ratios of Mn³⁺/Mn⁴⁺are followed recently. In this work,we deposit the doped LaMnO3and BiFeO₃multiferroics films and have a study onthe structural and physical properties. The main work are summarized as follows:1. The rhombohedra La_1-xK_xMnO₃（x=0.05,0.10,0.15and0.20） andLa_0.95-xCa_0.05K_xMnO₃（x=0.05,0.10,0.15and0.20） films are fabricated on single Si（100） substrate by chemical solution deposition （CSD） method. And there is no CMReffects in these films.2. The cubic perovskite thin films of La_1-xK_xMnO₃（x=0.05,0.1,0.15and0.20） on thesingle crystal LaAlO3substrate are prepared by CSD method. The thin films arehighly oriented along （h00） and the concentration of K dopants dominates the ratiosof Mn⁴⁺/Mn³⁺in the thin films. The value of Mn⁴⁺/Mn³⁺increases with increasing Kcontent, which results in the increasing Tcand insulator-metal temperature （TIM） with x. The maximum magnetoresistance ratio is44.7%at240K and2.0T for the x=0.05sample.3. The cubic perovskite thin films of La_0.95-xCa_0.05K_xMnO₃/LAO （x=0.05,0.10,0.15and0.20） are prepared by CSD method. The values of Tcand TIMcan be increased bycodoping K in La0.95Ca0.05MnO3. The magnetic entropy change increases withincreasing x, the maximum of the films is0.398kJ/K when x=0.15.4. BiFeO₃films are grown on ITO/glass substrate by CSD method. It is found that thefilms growth along （101） crystal orientation and have a plat and smooth surface. Thefilms present ferromagnetic behavior, the magnetization easy axis is along （101）. Thesaturation polarization is about51.3μC/cm².