| Summary: | 碩士 === 國立中山大學 === 物理學系研究所 === 91 === Abstract
The interaction between the multilayer of Antiferromagnetic(AFM)/
Ferromagnetic(FM) film have been one of the focal point in scientific and technology. In our preliminary result the enhancement on the low field magnetoresistance of AFM-La0.67Sr1.33MnO4 and FM-La0.67Ca0.33MnO3 mixture is obvious. It is, therefore, worthwhile to make it into a form of multilayer as the tunneling magnetoresistance (TMR) structure. This project was planed to start at a bilayer film of AFM-La0.67Sr1.33MnO4/ FM-La0.67Ca0.33MnO3 on SrTiO3(100) substrate by an off-axis RF sputtering system. Experiment at high temperature region (T＞70K) exhibits normal colossal magnetoresistance (CMR) behavior. A small cusp appears in R-T curve between 50~70K which is believed due to the quantum fluctuation initiated from AFM layer acted on the AFM/FM interface. However, the MR properties at this region shows abnormal phenomenon. The MR curve strongly depends on the sample posture during measurement when the relative geometry between the applied field, the applied current and the sample surface is fixed. The reason of this abnormal phenomenon is not clear yet and worth for further study .
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