The RKKY coupling in diluted magnetic semiconductors
  This paper is an attempt to modify the classic Ruderman-Kittel-Kasuya-Yosida (RKKY) model to allow the analysis of the magnetic resonance measurements. In our calculations, we follow the treatment of the original authors of the RKKY model but include the finite band splitting, {\Delta}, as a phenomenological parameter. The RKKY exchange is not anymore of Heisenberg type and an anisotropy induced by the direction of carrier magnetization occurs. 
A. Werpachowska and Z. Wilamowski
cond-mat.mtrl-sci