The Enhancement of Magnetoresistance in La1-xAxMnO3(A=Sr,Ca) films

• Main Authors: Min-Nan Ou, 歐敏男
• Other Authors: 周雄
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/86943028737882052442

碩士 === 國立中山大學 === 物理學系研究所 === 88 === Abstract It is know that the crystal structure and the magnetic ordering in La1-xAxMnO3(A=Ca,Sr,Ba) may disrupted by introducing various defect. This disorder weakens the Hund coupling and, thus, the double-exchange interaction between Mn3+ and Mn4+. Combining with John-Teller distortion enhanced by the defects, the magnetoresistance (MR) effect is enhanced. Up to date, the generated defects were mostly columnar defects or chemical substitution defects. In this study we generated different type of defect, point defects, and inrestigate its effect on MR effect. La0.7Sr0.3MnO3 and La0.7A0.3MnO3 films were deposit on LaAiO3 (001) and SrTiO3 (001) substrates by pulse laser deposition technique. Films were patterned with a standard photolithography. Point defects were introduced by irradiated high (1.7 and 3MeV) and low (10KeV) energy protons. We found that, the low dose sample exhibits both conductivity and the low field MR enhancement. Which were believed due to introduce acceptor level and the magnetic structure defects. When the dose was high, the structure defects leaded strong scattering effect that lowed the conductivity. The MR in high dose sample was also enhanced near by transition temperature.