| Magnetic material as one of the oldest functional materials and have lots of potentially technological application values in the technological age. Such as, the development of electrical, electronic industry, national defense construction and the improvement of people’s daily life have a huge effect. The perovskite manganites have been studied extensively due to their outstanding physical phenomena, such as, change-orbital ordered, phase separation, anisotrpy and electrical properties. Among the numerous interesting physical properties exhibited by the perovskite manganites, the cooperative orbital and/or charge ordering(OO/CO) phenomena are very fascinating. Included in this category are many of the perovskite manganites which display first order field-induced transitions in an applied field at low temperatures from an antiferromagnetic charge orbital ordered insulating(COOI) phase to a ferromagnetic metallic phase. In the case of the manganites, the phases typically coexist in low magnetic fields, and the metamagnetic transitions progress through an increasing fraction of the ferromagnetic phase in the phase-separated materials. At the same time, a single Lax Sr1-x O3 layer in the phase separation state can be considered as the simplest system for exchange bias since it has a higher TC than TN; therefore, a conventional field cooling process through the TN is possible. So, the effect of magnetic field on the two-layer pervoskite manganites Pr(Sr0.1Ca0.9)2Mn2O7(PSCMO) and the in the PSCMO film have been researched in the thesis, in order to study how to control the exchange bias effect in this category. The main results including two aspects are as following:1. The single-phase two-layer pervoskite manganites PSCMO has been prepared by the Sol-Gel method, and the crystal structure of the sample is orthogonal structure with space group Am2 m by the XRD analysis. Without the external magnetic field, the sample shows the like clusters glass state with the freezing temperature of 41 K mainly made up of antiferromagnetic phase in the low temperature, and its resistance shows a semiconductor or insulating properties. There is an obvious magnetic jump of magnetization in the sample at 3K M-H curves when an external magnetic field reaches to 5.7T. The magnetization with the 3 and 5T magnetic field pre-application has been gradually increased to five times and 28 times of the no-magnetic field pre-application. However, after an pre-application of 7T an external magnetic field at 5K, the magnetization has increased 150 times. So, the magnetic jump induced by 5.7T magnetic field is mainly due to the magnetic phase transition from antiferromagnetic clusters glass state to the ferromagnetic state.2. The PSCMO film on Pt/Ti/Si O2/Si substrate has been prepared by pulsed laser deposition, and the microstructure of the films has been measured by the X-ray diffractometer(XRD) and scanning electron microscopy. The results suggest that the films are polycrystalline of single phase, and the film grows with columnar grains perpendicular to the substrate with thicknesses are 900 nm. At the same time, we also studied the exchange bias effect and magnetic properties respectively in the M-H curves at 5K with magnetic field cooling in PSCMO films. The M- H curve after magnetic field cooling shows the exchange bias about y-axis symmetrical, and the exchange bias reached 3.0 × 10-6emu at 5K under the applied magnetic field of 2000 Oe. The exchange bias gradually increases with magnetic field, gradually reduces with the increasing temperature and disappears at 60 K. The coexistence and content of ferromagnetic and antiferromagnetic phases in the film is the main reason for the exchange bias effect with the study of the magnetic properties in PSCMO block. |
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