title: Arrays of ultrasmall metal rings.
abstract: In this paper, we present a simple method to fabricate ultra-high-density hexagonal arrays of ferromagnetic nanorings having 13 nm outer diameter, 5 nm inner diameter and 5 nm thickness. Cobalt magnetic nanorings were fabricated using a self-assembled diblock copolymer template with an angular evaporation of metal followed by an ion-beam etching. Magnetic measurements and theoretical calculations suggest that, at low fields, only the single domain and vortex states are important for rings of this size. The measured magnetization as a function of applied field shows a hysteresis that is consistent. These ultrasmall ferromagnetic rings have potential use in magnetic memory devices due to the simplicity of the preparation coupled with the ultra-high-density and geometry-controlled switching. This fabrication technique can be extended to other materials for applications in optics, sensing and nanoscale research.
authors.affiliation: Department of Physics, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: Deepak K
authors.initials: DK
authors.lastname: Singh
authors.forename: Robert V
authors.initials: RV
authors.lastname: Krotkov
authors.forename: Hongqi
authors.initials: H
authors.lastname: Xiang
authors.forename: Ting
authors.initials: T
authors.lastname: Xu
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Russell
authors.forename: Mark T
authors.initials: MT
authors.lastname: Tuominen