Studies On The Electrical And Magnetic Properties Of Fe-MgO Magnetic Granular Films

The cluster size and distribution is essential for understanding the transport property in magnetic granular thin films. We can get different results by changing the cluster size and distribution. Although FM-I granular films has been well studies, there are still many difficulties because of the lack of well-defined samples. The granular usually are prepared by co-sputtering or co-evaporation of the metallic and insulating component onto a substrate or by the reactive sputtering of metallic components. Granular systems prepared by the method given above have a broad distribution in cluster size and distance between clusters is random. Therefore, it is difficult to study the infl films uence of cluster size on physical properties of these systems.In this paper, we use sequential deposition method to fabricate Fe-MgO granular films with different Fe content, which is at the origin of the almost self-organized growth. The nominal thickness of every layer is no more than 1 nm. The large difference between the surface energies of Fe and MgO leads to a three-dimensional growth of Fe granules. In contrast with the co-deposition, the samples made by the sequential deposition method have well-distributed and almost monodisperse nanoparticles in a solid matrix, which is important for studying the influence of cluster size and distribution on MR. As far as we know, there is no report about the GMR in Fe-MgO granular films prepared by this method. We display results of an extensive study of conduction mechanism and the temperature dependence of magnetoresistance in such monodisperse granular films for temperature 15-300K. The mainly works and results are listed as following:(1) A series of Fe-MgO granular films with different Fe content were made by sequential deposition method based on self-organized growth, and the composition was studied by XPS. (2) The relation of MR and resistivity at different temperature was studied and it is found that the MR takes a maximum of 0.58% at room temperature and 0.74% at 15 K at H= 5000 Gs when the resistivity of sample is 4*10～7*106μΩcm.(3) The magnetization curve of samples show no hysteresis and follow well the Langevin function, which suggests the superparamagnetic nature.(4) our samples don't conform to the Inρ∝T -n, while accord withρ～exp (T0/T) 1/4 for resistance network model,which is different to the hopping transport in co-deposition samples(5) The temperature dependence of MR was special studied and it is found that MR-T dependence is linear for temperature 15-300 K, which is related to the special microstructure of the samples。...