【摘要】 用射频磁控溅射方法制备了系列Co SiO₂ 不连续磁性金属绝缘体多层膜 （DMIM） .经研究发现 :对 [SiO₂ （2 4nm） Co（t） ]2 0 体系 ,在Co层厚度小于 2 5nm时 ,Co层由连续变为不连续 ;Co层不连续时 ,其导电机理为热激发的电子隧穿导电 ,lnR与T- 1 2 接近正比关系 ;隧道磁电阻 （TMR）在Co层厚度为 1 4nm时出现极大值 - 3% .DMIM的性质不仅与磁性金属层厚度密切相关 ,而且与绝缘层厚度有密切的关系 .在固定Co层厚度为 1 9nm的情况下 ,研究了TMR随SiO₂ 层厚度的变化关系 ,并给出定性的解释 .对 [SiO₂ （2 4nm） Co（2 0nm） ]2 0 的样品研究了TMR随温度的变化关系 ,发现TMR随温度的变化有一极大值 ,结合Helman的理论 （Phys.Rev .Lett,37,14 2 9（1976 ） ） ,认为是颗粒之间存在磁性耦合的结果更多还原

【Abstract】 A series of discontinuous magnetic metal/insulator multilayers （DMIM） of Co/SiO₂ is fabricated using radio_frequency magnetron sputtering technique. For [SiO₂ （2.4 nm）/ Co （t）]₂₀, it is found that Co layer changes from continuous to discontinuous for its thickness smaller than 2.5 nm; the logarithmic resistivity ln（ρ） is nearly proportional to T^-1/2 when the Co layer is discontinuous, indicating a thermal excitation tunneling mechanism. The tunneling magnetoresistance （TMR） has a maximum value of -3% when the thickness of the Co layer is 1.4 nm. The property of DMIM not only depends strongly on the thickness of magnetic metal, but also the thickness of the insulator. The relationship between the TMR ratio and the thickness of SiO₂ is investigated taking the Co layer thickness at a constant value of 1.9 nm, and we give a qualitative explanation to it. The dependence of TMR of [SiO₂（2.4 nm）/ Co（2.0 nm）]₂₀ on temperature is studied, and it is found that the TMR as a function of temperature, has a maximum value which originates from the magnetic coupling among the magnetic granules, taking into account the theory of Helman [Phys. Rev. Lett, 37, 1429 （1976）].更多还原