title: Graphene activating room-temperature ferromagnetic exchange in cobalt-doped ZnO dilute magnetic semiconductor quantum dots.
abstract: Control over the magnetic interactions in dilute magnetic semiconductor quantum dots (DMSQDs) is a key issue to future development of nanometer-sized integrated "spintronic" devices. However, manipulating the magnetic coupling between impurity ions in DMSQDs remains a great challenge because of the intrinsic quantum confinement effects and self-purification of the quantum dots. Here, we propose a hybrid structure to achieve room-temperature ferromagnetic interactions in DMSQDs, via engineering the density and nature of the energy states at the Fermi level. This idea has been applied to Co-doped ZnO DMSQDs where the growth of a reduced graphene oxide shell around the Zn(0.98)Co(0.02)O core turns the magnetic interactions from paramagnetic to ferromagnetic at room temperature, due to the hybridization of 2p(z) orbitals of graphene and 3d obitals of Co(2+)-oxygen-vacancy complexes. This design may open up a kind of possibility for manipulating the magnetism of doped oxide nanostructures.
authors.affiliation: National Synchrotron Radiation Laboratory, University of Science and Technology of China , Hefei, Anhui 230029, People's Republic of China.
authors.forename: Zhihu
authors.initials: Z
authors.lastname: Sun
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Yang
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.forename: Tao
authors.initials: T
authors.lastname: Yao
authors.forename: Liang
authors.initials: L
authors.lastname: Cai
authors.forename: Wensheng
authors.initials: W
authors.lastname: Yan
authors.forename: Yong
authors.initials: Y
authors.lastname: Jiang
authors.forename: Fengchun
authors.initials: F
authors.lastname: Hu
authors.forename: Jingfu
authors.initials: J
authors.lastname: He
authors.forename: Zhiyun
authors.initials: Z
authors.lastname: Pan
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Liu
authors.forename: Shiqiang
authors.initials: S
authors.lastname: Wei
keywords: Co-doped ZnO QDs; RGO; XAFS; ferromagnetic exchange