The resistivity increases gradually with decreasing temperature and varies slightly from 0.0093 Ω · cm (T = 300 K) to 0.011 Ω · cm (T = 5 K). Combined with the structure of sample A, the transport process is probably dominated by metallic paths because of the large number of interconnected elongated Co particles (see Figure 3a), which decreases when the resistivity increases, accompanying an increased MR effect. The approximate linear relationship between ρ and ln T for sample A is shown in Figure 5f. The fitting value of straight slope is shown in Table 1. The same phenomenon was reported in a CoO-coated monodispersive Co cluster system

corresponding to a small negative MR value in a metal/semiconductor transition regime [30] and in the CoFeB/MgO films, in which the sample with high magnetic metal concentration is not in the strongly localized regime of conduction and the resistivity Captisol nmr is plotted as a linear function of log(T) [31]. Further detailed studies are

necessary and in progress to elucidate the mechanism behind this result. Conclusions In summary, the structure, magnetic properties, and MR effect were investigated in Co/ZnO films deposited by sputtering at different pressures with different ZnO contents. We observed that the MR effect is strongly related to the resistivity Nepicastat cell line of the films. Based on conduction, the MR effect can be classified into three regimes: the metallic, tunneling, and hopping regimes. Large RT MR values greater than 8.1% were obtained in the tunneling regime with a range of resistivity from 0.08 to 0.5 Ω · cm. By

contrast, the MR value decreases distinctly when the resistivity of the films is less than 0.08 Ω · cm (metallic regime) or greater than 0.5 Ω · cm (hopping regime). In the tunneling regime, the conduction of the films mainly has two channels: the spin-dependent tunneling channel, which gives rise to high RT MR effect, and the learn more spin-independent second-order hopping (N = 2). In the hopping regime, Metalloexopeptidase the increased spin-independent higher-order hopping (N > 2) through the localized states in thicker ZnO matrix served an important function and is the main reason for the rapid decrease in tunneling MR. In the metallic regime, metallic paths between interconnected elongated Co particles impede the MR effect. These results facilitate a deeper understanding of the spin transport mechanism in metal/semiconductor granular films and are significant for the improvement of the RT MR effect in spintronic applications. Acknowledgements The work is financially supported by NSFC (nos. 51025101 and 11274214), the Special Funds of Shanxi Scholars Program, the Ministry of Education of China (nos. IRT 1156 and 20121404130001), and the Youth Science Foundation of Shanxi Province (2012021020–2). References 1.