Non-Ohmic Behavior in Sintered La1-xSrxMnO3 Magnetic Oxide

• Main Authors: Wen Cheng Hung, 溫政宏
• Other Authors: C. M. Fucm
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/38155723457268027166

碩士 === 國立高雄師範大學 === 物理學系 === 87 === In this thesis, we have systematically studied the current-voltage (I-V) characteristics of the sintered La1-xSrxMnO3 magnetic oxides. Experimental results have shown a specific I-V feature in certain temperature region, which can be characterized as following. First, at initial and small biased current, the voltage is linearly proportion to the applied current. Further increasing the biased current, the voltages deviate from the linearity gradually, and demonstrate a non-ohmic behavior. As the biased current exceed a threshold value, the voltage pass a maximum and decreases while the biased current is increasing, which demonstrate a sign of negative differential resistance. Furthermore, measurements of La1-xSrxMnO3 with various composition x have shown that the I-V behavior is strongly dependent on insulator/metal phase states. The I-V characteristic at non-ohmic region follows the Poole-Frenkel relation: lnIμ V1/2 ,impling the occurrence of field-assisted emission of carriers from coulombic centers. At the negative differential resistance region, the differential resistance follows the relation of Rnegμ exp(-V-1/4), indicating attribution of the hopping mechanism. Utilizing the fitting parameters analyzed from above mentioned theories, we can calculate the activation energy、hopping distance and the density of localized states near Fermi level. The analyzed results may provide a fundamental to disclose the CMR physics phenomena in manganese oxides, and possible application of magneto-electronic devices.