The electronic and magnetic properties of individual Fe atoms adsorbed on the surface of the topological insulator ${\mathrm{Bi}}_2{\mathrm{Te}}_3$(111) are investigated. Scanning tunneling microscopy and spectroscopy prove the existence of two distinct types of Fe species, while our first-principles calculations assign them to Fe adatoms in the hcp and fcc hollow sites. The combination of x-ray magnetic circular dichroism measurements and angular dependent magnetization curves reveals out-of-plane anisotropies for both species with anisotropy constants of $K_{\text{fcc}}=(10\pm 4)$ meV/atom and $K_{\text{hcp}}=(8\pm 4)$ meV/atom. These values are well in line with the results of calculations.

• Received 8 October 2013
• Revised 6 March 2014

DOI:https://doi.org/10.1103/PhysRevB.89.104424