Abstract Monitoring magnetoelectric transport behavior of graphene material is critical in establishing a foundation for engineering next-generation spintronic devices. Here we report a temperature-dependent crossover between positive and negative magnetoresistance (MR) in graphene nanocrystallines embedded carbon film (GNC film), two sign changes of MRTotal (where MRTotal presents the measured MR value) value from positive MRTotal(+) to negative MRTotal(−) and then back to MRTotal(+) are observed as temperature varies from 2 K to 400 K. The crossover can be ascribed to the competitions among different origins including wave function shrinkage, spin-dependent Coulomb blockade effect and Lorentz force, which play dominant roles in low, medium and high temperatures, respectively. Moreover, it is revealed that GNC film with smaller GNs has larger positive contribution to MRTotal behavior, resulting in maximum MRTotal(+) of ∼8.1%. In contrast, GNC film with larger GNs dramatically contributes to negative MRTotal behavior, which obtains maximum MRTotal(−) of ∼ -1.1%. This work deepens understanding about the origin of MR of nanometer-sized graphene, which provides guidance for further magnetoelectric property improvement, and paves a way towards specific design of graphene derived spintronic devices with controllable MR behavior.

中文翻译：

---

石墨烯纳米晶嵌入碳膜中正负磁阻之间的温度相关交叉

摘要 监测石墨烯材料的磁电传输行为对于为下一代自旋电子器件工程奠定基础至关重要。在这里，我们报告了石墨烯纳米晶嵌入碳膜（GNC 膜）中正负磁阻 (MR) 之间的温度相关交叉，MRTotal（其中 MRTotal 表示测量的 MR 值）值从正 MRTotal(+) 到负的两个符号变化当温度从 2 K 到 400 K 变化时，观察到 MRTotal(-) 然后回到 MRTotal(+)。交叉可以归因于不同起源之间的竞争，包括波函数收缩、自旋相关库仑阻塞效应和洛伦兹力，分别在低温、中温和高温中起主导作用。而且，结果表明，具有较小 GN 的 GNC 膜对 MRTotal 行为具有更大的积极贡献，导致最大 MRTotal(+) 为 ~8.1%。相比之下，具有较大 GN 的 GNC 膜显着有助于负 MRTotal 行为，其获得最大 MRTotal(-) ~ -1.1%。这项工作加深了对纳米级石墨烯MR起源的理解，为进一步提高磁电性能提供了指导，并为特定设计具有可控MR行为的石墨烯衍生自旋电子器件铺平了道路。