title: Realizing ferromagnetic coupling in diluted magnetic semiconductor quantum dots.
abstract: Manipulating the ferromagnetic interactions in diluted magnetic semiconductor quantum dots (DMSQDs) is a central theme to the development of next-generation spin-based information technologies, but this remains a great challenge because of the intrinsic antiferromagnetic coupling between impurity ions therein. Here, we propose an effective approach capable of activating ferromagnetic exchange in ZnO-based DMSQDs, by virtue of a core/shell structure that engineers the energy level of the magnetic impurity 3d levels relative to the band edge. This idea has been successfully applied to Zn(0.96)Co(0.04)O DMSQDs covered by a shell of ZnS or Ag2S. First-principles calculations further indicate that covering a ZnS shell around the Co-doped ZnO core drives a transition of antiferromagnetic-to-ferromagnetic interaction, which occurs within an effective depth of 1.2 nm underneath the surface in the core. This design opens up new possibility for effective manipulation of exchange interactions in doped oxide nanostructures for future spintronics applications.
authors.affiliation: National Synchrotron Radiation Laboratory, University of Science and Technology of China , Hefei, Anhui 230029, China.
authors.forename: Wensheng
authors.initials: W
authors.lastname: Yan
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Liu
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Yang
authors.forename: Tao
authors.initials: T
authors.lastname: Yao
authors.forename: Jingfu
authors.initials: J
authors.lastname: He
authors.forename: Zhihu
authors.initials: Z
authors.lastname: Sun
authors.forename: Zhiyun
authors.initials: Z
authors.lastname: Pan
authors.forename: Fengchun
authors.initials: F
authors.lastname: Hu
authors.forename: Ziyu
authors.initials: Z
authors.lastname: Wu
authors.forename: Zhi
authors.initials: Z
authors.lastname: Xie
authors.forename: Shiqiang
authors.initials: S
authors.lastname: Wei