Study On Structure, Property Of La_0.9Ba_0.1MnO_3-δ Thin Film And La_0.67Pb_0.33Mn_1-xTi_xO₃

In recent years,the colossal magneto-resistance effect in rare-earth manganite perovskites Ln_1-xA_xMnO₃(where Ln was rear-earth irons La²⁺,Nd²⁺,Pr²⁺;A was alkaline earth iron Ca²⁺,Sr²⁺,Ba²⁺) had attracted considerable attention in scientific studies due to its potential application.However,there were also many difficulties for this kind of magnetoresistance material in practical applications,such as:generation of CMR effect needed a strong applied magnetic field,usually several Teslas,the peak values of CMR materials mostly appeared in the low temperature area,the sharp changes of MR happened in a very narrow temperature range,these factors set a big limit in the applications of this kind of materials.At present,the researches mainly focused on nearby-room-temperature and low field CMR effect,especially the studies on A-site Sr and Ca doping,the reports about substituting Ba or Pb for A-site La were still not many,substituting Pb and Ti for A-site La and B-site Mn simultaneously hadn't been reported by now.In this article,on the basis of the prepration of La_0.9Ba_0.1MnO_3-δ thin film material and La₍0.67_Pb_0.33Mn_1-xTi_xO₃ bulk material,by the systemic research and analysis on the structures and physical properties of these tow materials,some significant results were aquired.La_0.9Ba₍0.1_MnO_3-δ(LBMO) thin film which were deposited on Si(100) single crystal substrate by the RF magnetron sputtering were annealing at different temperature.X-ray diffraction(XRD),scanning tunneling microscope(STM),X-ray photoelectron spectroscopy(XPS),and four probe methods were respectively used to measure the phase structures,the morphologies,surface state and magnetism property. The study results show the grains of LBMO films annealed in range of 800℃～850℃had an epitaxial relationship with Si(100) substrate,the measuring results show that different annealing temperature lead to the quantity of oxygen changing in thin film.Magnetoresistance of the thin film which were annealed at 850℃arrive at about 30%when the temperature reach 300k and the magnetic field reach 1.6k.A series of manganite perovskite polycrystalline samples of La₀₆₇Pb_0.33Mn_1-xTi_x -O₃(x=0,0.02,0.05,0.1,0.15,0.2)were prepared by solid state reaction in the air. The XRD analyses and SEM images observation of these samples indicated that the quantity of the doped Ti ion to be bigger,the crystal grain to be also bigger.Compar -ed to other doping samples,the undoped La_0.67Pb_0.33MnO₃ crystal grain was least. The samples'infrared absorption spectra had been measured at room temperature and all samples appeared the absorption peak in the range of 601～571cm^-1.The peak moved from lower frequency to higher frequency along with the doping ionic quantity increasing.Magnetic property survey of the samples indicated quantity of the doping Ti ion had important effect on magnetoresistance(MR) of the sample.