Study On Electrical Properties Of Pr_0.5Sr_0.5MnO₃ Film

In this paper, Pr0.5Sr0.5MnO3 (PSMO) films on single crystal substrates of LaAlO3 (LAO) were fabricated by pulsed-laser deposition method (PLD). During film depositing process, several methods had been applied to improve the film quality. Out-of-plane lattice parameter was determined by x-ray diffraction (XRD). Magnetization and resistivity under various magnetic and electric field as a function of temperature were tested respectively by physical property measurement system (PPMS) and superconducting quantum interference device (SQUID).We studied the influence of film thickness on the structure and electrical properties of the films by depositing various thickness films raging from 60 nm to 400 nm. In 60 nm thickness films, the resistance was found greatly sensitive to the electrical current and magnetic field in low-temperature antiferro magnetic insulating state, ie. Clossal magneto re sistence (CMR) and Clossal electrocresistence (CMR). With increasing film thickness both the electroresistance and magnetoresistance are greatly suppressed. The thickness dependence of electroresistance and magnetoresistance could be explained by the influence of strain on phase separation and competition. Then, we studied the effect of post-annealing process on film electrical properties. The in-situ-grown films show paramagnetism-ferromagnetism transition upon cooling, and finally get into antiferromagnetic-insulating state in low temperature. However, the annealed films are ferromagnetic and metallic in ground state. These changes of electrical properties are demonstrated to be caused by the strain relaxation during the post-annealing process.This study implies that the manganites located at phase boundary may be an ideal compound for providing practical colossal effects of elastoresistance, electroresistance and magnetoresistance.