The magnetoresistance of Co-Cu and Co-Cu-Nb alloy films

• Main Authors: Chen, Wen Cheng, 陳文程
• Other Authors: Yen Hwei Chang, Ming Pan Hung
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/13803084446645548591

碩士 === 國立成功大學 === 材料科學(工程)學系 === 84 === The Co-Cu binary and Co-Cu-Nb ternary alloy films were prepared by DC magnetron sputter deposition method. The films were then heat-treated at the temperature among 250℃and 550℃ for one hour . We studied the magnetoresistance characteristic by changing the heat-treated temperature and the chemical composition. The magnetoresistance were measured at room temperature (300oK) and low temperature (80o K) and the external magnetic field until 14KOe . The identification of phase and the microstructure withithe specimens were achieved by the X-ray diffraction and TEM. The binary alloy films showed nearly supermagnetism due to the magnetoresistance linearly changed with magnetic field . When it contained higher Co concentration , the magnetoresistance changed nearly sguare to the magnetic field , then the films showed ferromagnetism. The films had the best magnetoresistance characteristic when it contained Co 28.8 at% in the binary alloy films . We achieved higher magnetoresistance ratio by heat-treating films appropriately, which can develope the formation of magnetic phase . As N5 system alloy films were then heat-treated at 450℃for one hour , we found that the precipitation of magnetic particles became much more and distributed uniformly . Since the larger surface to volume ratio , the interface scattering effect became prominent, so the magnetoresistance ratio could advance to 3.423% at room temperature(The external magnetic field are 14 KOe ). This was the highest ratio we could obtain in the work. When we measured at low temperature, the MR ratio could reach to 6.22% . We added the third element Nb according to the Co28.8 Cu71.2 alloy films . The films nanocrystallized when the Nb amount increased. A little addition of Nb element might have contribution to the MR effect at constant Co contain.The MR ratio decreased when adding Nb element at constant Cu contain. After the appropriate heat-treated in ternary alloy films , we could get higher value of MR ratio , and when the heat-treated temperature increased , we could obtain the saturated MR ratio at lower magnetic field .