Strong out-of-plane magnetic anisotropy of Fe adatoms on Bi2Te3

The electronic and magnetic properties of individual Fe atoms adsorbed on the surface of the topological insulator Bi2Te3(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-fcc = (10 +/- 4) meV/atom and K-hcp = (8 +/- 4) meV/atom. These values are well in line with the results of calculations.