掺银磁铁矿复合薄膜的制备及室温磁电阻效应  

Preparation and room-temperature magnetoresistance effect of silver-doped magnetite composite films

作　　者：王子生[1] 胡秀坤[1] 吴琼[1] 徐美华[2,3] 

机构地区：[1]中国计量学院材料科学与工程学院,浙江省磁学重点实验室,浙江杭州310018 [2]南京大学物理系,固体微结构国家重点实验室,江苏南京210093 [3]南京工业大学应用物理系,江苏南京210009

出　　处：《电镀与涂饰》2009年第7期63-66,71,共5页Electroplating & Finishing

摘　　要：采用溶胶–凝胶技术结合旋涂法,以聚乙烯醇作为鳌合剂,选择适当的退火程序,制备了由金属Ag相和Fe3O4相所组成的Agx(Fe3O4)1-x(x=0,0.1,0.2,0.3)复合薄膜。磁力显微镜观察表明,Fe3O4晶粒为单畴颗粒,其直径为75～85nm,小于理论计算的单畴临界尺寸。磁性测量表明:x=0.1和0.3薄膜的矫顽力HC分别为23.1kA/m和28.6kA/m,很接近于Fe3O4的磁晶各向异性场HK(27.1kA/m)。室温(300K)下,x=0.1的薄膜具有最大的磁电阻,700kA/m磁场下为-3.5%,高于纯Fe3O4薄膜的低场磁电阻(-2.2%)。随着Ag含量进一步增加,薄膜的室温磁电阻减小。适量金属Ag的掺入有利于提高Fe3O4薄膜的磁电阻,这归因于自旋极化电子在Fe3O4晶粒和Ag颗粒界面处的自旋相关散射以及穿过Fe3O4–Fe3O4晶界的自旋极化隧穿的共同作用。Agx（Fe3O4）1-x （x = 0, 0.1, 0.2 and 0.3） composite thin films consisting of a ferrimagnetic spinel Fe3O4 phase and a non-magnetic metal Ag phase were prepared by sol-gel method in combination with spin-coating technique. The microstructure observation of the thin films by magnetic force microscope indicated that the Fe3O4 grains are nearly spherical with a diameter ranging from 75 nm to 85 nm which is less than the theoretically calculated critical diameter of single-domain Fe3O4 particles. The coercivity of the films is about 23.1 kA/m for the thin film with x = 0.1 and 28.6 kA/m for that with x = 0,3 respectively, which are nearly equal to the magnetocrystalline anisotropy field HK of Fe3O4 （namely 27.1 kA/m）. At room temperature （300 K）, the thin film with x = 0.1 has a maximal magnetoresistance of-3.5% under a magnetic field of 700 kA/m, which is higher than that （-2.2%） of a pure Fe3O4 film. The magnetoresistance is decreased with further increasing Ag content. Therefore, an appropriate addition of Ag is favorable for the enhancement of the roomtemperature magnetoresistance of Fe3O4 thin film, which can be attributed to the combined effect of the spindependent scattering at the interfaces between Fe3O4 grains and Ag granules as well as the spin-polarized tunneling at boundaries between Fe3O4 grains of spin-polarized electrons.

关 键 词：磁铁矿 掺银 非本征磁电阻效应 室温 单畴 溶胶-凝胶法 

分 类 号：TM271[一般工业技术—材料科学与工程] O484.1[电气工程—电工理论与新技术]