Fabricated And Electrical Researched The Heterojuction Of Lanthanide Manganese Oxides And Silicon

Lanthanide manganese oxides of the general formula La_1-xA_xMnO₃ (where A is alkaline-earth ions, such as Ca, Sr and Ba) have attracted much attention because of their distinctive properties, especially the colossal magnetoresistance (CMR) effect. Such perovskite-like oxides exhibit a rich variety of electronic, magnetic, and structural properties at different temperatures as the doping level x changed.Phase separation together with concomitant percolation behavior has been supposed to be the core of CMR effect. It has been suggested that the largest MR is associated with spatial inhomogeneity related to multiphase coexistence, which generically causes a sensitivity of physical properties to external perturbations, such as application of magnetic fields, pressure, current bias, or light illumination.Several reports proved that the balance of multiphase coexistence can be influenced not only by a magnetic field but also by an electric field or current bias. Considering the strong effect of external perturbations, especially magnetic field and current bias, on the balance of multiphase coexistence, it can be expected that an enough high magnetic field or current bias could thoroughly disturb the subtle balance of multiphase coexistence and then may induce a new equilibrium state of coexistence, in which different novel CMR characteristics might appear.However, the investigation of an extremely high field on the multiphase coexistence is not easy to be carried out due to the technological limitation of generating a very high magnetic field. Fortunately, a current with very high density could be easily applied to a CMR thin film and thus the influence of high current density on the multiphase coexistence state can be investigated.Furthermore, oxygen pressure is another important factor which dramatically affects the physical properties of materials of strong electron correlation. For instance, the critical temperature of a high-Tc superconductor is quite sensitive to its oxygen pressure.The present La_0.9Sr_0.1MnO₃ thin films were grown on single crystal substrates of SrTiO₃ with (100) orientation using laser molecular beam epitaxy (LMBE) deposition technique under different oxygen pressure.It was found that the film deposited at lower oxygen pressure shows larger c-axis parameter, higher resistance, and more distinct electroresistance. Theses results reveal that the electroresistance of manganite thin films can be controlled and tuned by the conditions of film fabrication. The percolative phase separation model and the local heat effect can well explain this phenomenon.