The influence of MgO Addition on Magnetoresistance and Microstructure of Perovskite Oxides

• Main Authors: Chia-Lun Liu, 劉嘉倫
• Other Authors: L. H. Chen
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/65805386975211785098

碩士 === 義守大學 === 材料科學與工程學系 === 89 === In this work, the magnetoresistance behavior and microstructure have been studied for the A-site ion (Ca2+) deficient La0.67CaxMnO3-y and La0.67SrxMnO3-y (x= 0, 0.1, 0.2, 0.33) and MgO of 0-20 at% doped La0.67 CaxMgzMnO3-y and La0.67CaxMgzMnO3-y materials. The bulk materials were prepared by conventional powder metallurgy processes and films were deposited on (100) Si substrates by DC magnetron sputtering. The bulk La0.67Ca0.33MgzMnO3-y materials have a polycrystalline structure, in which the grain size decreases as a result of MgO Addition. The resistivity of bulk La0.67Ca0.33MgzMnO3-y materials decreases as the content of MgO increases. However, the MR ratio of materials is raised as the MgO is incorporated, which is as high as 566 % for the bulk material with MgO of 20 %. The effect of MgO addition on the structure and magneto-transport properties of bulk La0.67Sr0.33MgzMnO3-y materials is similar to that of of bulk La0.67Ca0.33MgzMnO3-y materials. The resistivity as well as the MR ratio of bulk La0.67CaxMgzMnO3-y materials with 2% MgO is reduced as the Ca2+ content increases. The La0.67Ca0.2MgzMnO3-y film with 20% MgO has an amorphous structure, which exists the crystalline La0.67Ca0.2MgzMnO3-y phase after annealing at temperatures of 850 C or higher for 2 hr. The as deposited La0.67Ca0.2MgzMnO3-y film exhibits a MR ratio of only 2.2%, which significantly increases to a value of 138% after annealing.