Stable single domain Co nanodisks: synthesis, structure and magnetism

Abstract

Colloidal synthesis of morphologically stable oxide-free cobalt nanodisks (diameter ≈ 21 nm, thickness ≈ 12 nm) has been achieved. The hcp c-axis is found to be perpendicular to the flat side of the disk which is explained by surface energy considerations. Magnetic measurements and comparisons with simulations show that the nanodisks are single magnetic domains with a magnetisation oriented perpendicular to the plane of the disks and reaching that of bulk cobalt, and high anisotropy field. These disks are thus potential candidates for magnetic data storage, magnetic sensor arrays, and cheap permanent magnets.