| Summary: | 碩士 === 國立臺灣大學 === 材料科學與工程學研究所 === 86 === The magnetoresistance properties of pellets of the (Fe3O4)X(Fe2
O3)1-X systems have been investigated. The samples were
prepared by reducing the α-Fe2O3 (99.8 %) powder in the
mixture of Ar (95 %) and H2 (5 %) atmosphere at 350 ℃. After
reducing, the powders were ground and pressed into pellet. The
pellets were then sintered in flowing He gas between 1100℃ and
1400℃ for 1 to 12 hours.
We found that the samples sintered at 1100 ℃ between 3 and 6
hours and sintered at 1200 ℃ between 1 and 3 hours had better
magnetoresistance properties. After sintering at 1100 ℃ for 3
hours, the MR ratio of the samples increases rapidly from 2.5 %
for X=0.185 to 4 % for X=0.4, then increase slowly with X to 5
% for X=0.95.
From the observation of X-Ray diffraction, the temperature
dependence of the resistivity ρ(T), and the I-V curves, we
found that the magnetoresistance properties of the (Fe3O4)X(Fe2
O3)1-X systems is belong to the spin dependent tunneling
mechanism.
|
|---|
