Research On The Resistive Switching Effect And The Electric-field Manipulation Of Magnetism In Magnetic Oxide Films

With the development of science and technology,there is a growing demand for information storage.At present,the research target of information storage is to find a novel nonvolatile memory with high-density,high-speed and low power consumption.To realize this object,the effect of electric field control of magnetization is a promising solution.An effective way to control magnetism via electric field is using the converse magnetoelectric effect in multiferroic material,in which magnetism is controlled by electric field rather than by magnetic field or electric current.With the development of the study of converse magnetoelectric effect,more and more problems emerge,such as the volatility of data and the incompatibility with CMOS,which greatly hinder the development of electric-field control of magnetism effect in practical applications.In this context,the electric field control of nonvolatile magnetization in a CMOS compatible structure is greatly desirable.Multilevel resistive switching effect has attracted more and more attention for the application in high-density information storage technology.The multilevel resistive switching effect can be observed in many materials,but the resistive switching performance is not stable,which becomes an obstacle for the practical application.Therefore,exploring new resistive switching mechanism and the multilevel resistive switching materials with high performance and good stability are of great importance.To address these issues,a series of studies are carried out in this dissertation,which can be divided into two parts:one is the electric field manipulation of magnetization in the magnetic oxides based on resistive switching effect,and the other is the multilevel resistive switching effect in La2/3Ba1/3MnO3 film.The main content and conclusions are as follows:1.Electric-field manipulation of magnetization in Au/NiO/Pt device with resistive switching effectAu/NiO/Pt device was prepared by the pulsed laser deposition(PLD).A typical unipolar resistance switching effect with good performance is observed in Au/NiO/Pt device.We measured the magnetization of the Au/NiO/Pt device with SQUID during the Set and Reset processes.The results indicate that the saturated magnetization(Ms)of the device can be changed by the resistive switching effect.The value of Ms for the device under LRS is larger than that under HRS.Furthermore,Ms of the device shows almost stable change after several cycles with the voltage triggering back and forth,suggesting that the magnetization of this device can be reversibly and reproducibly controlled by the electric field.This effect can be understood by the formation and rupture of the metallic Ni conducting filaments as a result of electric-field-induced migration of ions.2.Electric field modification of magnetism in Au/La2/3Ba1/3MnO3/Pt device with resistive effectLa2/33Ba1/3MnO3 thin films were deposited on the Pt/Ti/SiO2/Si substrates by pulsed laser deposition(PLD).A typical bipolar resistance switching effect with good performance is observed in this device.We measured the magnetization of the Au/La2/3Ba1/3MnO3/Pt device with SQUID during the Set and Reset processes.Ms of the Au/La2/3Ba1/3MnO3/Pt device shows almost stable change after several cycles with the voltage triggering back and forth,suggesting that the magnetization of this device can be reversibly and reproducibly controlled by the electric field.Moreover,unlike the effect of electric field control of magnetization in some magnetoelectric composites,the magnetization of the memory cells maintains unchanged by switching off the voltage,showing a nonvolatile behavior.Through this effect,the electric field manipulation of nonvolatile magnetization is achieved in this device,which can be understood by the break or repair of the-Mn3+-O2--Mn4+-chains induced by the electric field through the oxygen vacancies migration.3.Multilevel resistive switching effect in Au/La2/3Ba1/3MnO3/Pt deviceLa2/3Ba1/3MnO3 thin films were deposited on the Pt/Ti/SiO2/Si substrates by pulsed laser deposition(PLD).We studied the resistive switching effect of this device with a self-build measurement system.Our results show that a multilevel resistive switching effect modulated by the reset voltage is observed in the Au/La2/3Ba1/3MnO3/Pt device.The multilevel resistance states can be maintained up to more than 3500 cycles without any dramatic degradation,exhibiting an excellent and stable performance.This effect can be understood by the break or repair of the-Mn3+-O2--Mn4+-chains as a result of electric-field-induced migration of oxygen vacancies(or oxygen ions).4.Electric field modification of magnetism in Au/CoFe2O4/Pt device with resistive effectAu/CoFe2O4/Pt device was prepared by the pulsed laser deposition(PLD).A typical unipolar resistance switching effect with good performance is observed in Au/CoFe2O4/Pt device.The electric field manipulation of magnetization with resistive effect was in situ investigated by Atomic force microscopy(AFM)and magnetic force microscopy(MFM).The results indicate that the magnetization of the device can be changed by the resistive switching effect.The physical mechanism of this effect in the Au/CoFe2O4/Pt device is still being studied.