Electrical Pulse Induced Resistance Effects And Memristor Behavior In La_0.5Ca_0.5MnO₃Ceramics

Perovskite manganese oxide is a strongly correlated electron system and has abundant physical connotation, such as colossal magnetoresistance effect (CMR), spin-orbit-charge order,100%spin polarization and intrinsic electronic phase separation.In addition to the well-known unusual electrical and magnetic properties, the electric-pulse-induced resistance (EPIR) switching effect, which is connected with the colossal electroresistance and memristor behavior, is also one of the interesting novel exotic phenomena in manganites.The EPIR effect have been discovered by2000, but so far the physical origin and mechanism of it have not reached a unified understanding, and the intrinsic EPIR effect on perovskite manganite involving less. So this paper launches the research from these two aspects.In this work, La0.5Ca0.5MnO3(LCMO) ceramic samples were synthesized by solid state reaction, the sample heat treatment in different atmosphere to obtain the different oxygen content in samples. The transport properties, especially the EPIR effect and memristor behavior were investigated using2-wire and4-wire measurement mode. The results are as follows:1、The I-V curve, EPIR curve’s change trend with temperature and the R-T curve for LCMO ceramic samples were investigated using2-wire measurement mode. And we conclude that trap defects exist in surface of LCMO sample, then by space charge limited current (SCLC) model proved that trap defects in surface of LCMO sample is deep level trap defects. The change trend of EPIR effects of LCMO with the vacuum degree of measurement environmental and EPIR curves for samples sintered in different atmosphere show thar the vacancies act as deep traps defects. And we further proof of the charge and discharge behavior of defects under the effect of polar pulse is the cause to induce interface EPIR effect. 2、The transport properties, especially the EPIR effect and memristor behavior were investigated using4-wire measurement mode. Although the Ⅰ-Ⅴ curve of LCMO shows an ohmic linearity under the4-wire mode at room temperature, a stable and remarkable EPIR effect can still be observed when the voltage of the electrical pulse is more than a threshold value. The4-wire mode eliminates the contact resistance between the sample surface and the metal electrode, and measurements mainly reflect the body resistance of samples, so we called it intrinsic EPIR effect. When we change the sintering environment and measurement environmental, the intrinsic EPIR effect is not affected, and has a good anti-fatigue and retention property.3、By comparing the intrinsic EPIR effect under4-wire mode and surface effect under2-wire mode, found that the intrinsic EPIR of LCMO has smaller pulse threshold voltage and better anti-fatigue properties, and it is not affected by the measurement environmental and sintering environment, so we think this bulk EPIR effect is novel for rare-earth doped manganites.