Magnetic anisotropy of thin Co and Ni films on diamond surfaces

Stärk B, Krüger P, Pollmann J

Abstract

We present results of ab initio investigations of magnetic properties of Co and Ni multilayers on diamond surfaces. The generalized gradient approximation is used within the framework of noncollinear density-functional theory, and fully relativistic pseudopotentials are employed together with a basis set of Gaussian orbitals. The validity of this approach is demonstrated for freestanding transition-metal (TM) monolayers and TM monolayers on the Cu(001) surface. Our results for these test systems are in good agreement with respective literature data. We employ the approach to study up to six Co or Ni adlayers on (111) and (001) surfaces of diamond. These systems are characterized by a very small lattice mismatch of the constituents. We analyze the influence of the strong covalent bonds forming in these hybrid systems on the magnetic properties, focusing on the magnetic anisotropy. For Co multilayers on C(111), the anisotropy energies are quite large and show a weak dependence on the number of adlayers. For Co or Ni multilayers on C(001), on the other hand, these energies are an order of magnitude smaller but their dependence on adlayer thickness is much more pronounced. For the hybrid systems considered, we find configurations with noncollinear magnetization within a given layer or on different layers to be unstable.