Calculations of electronic structure of Ge₄₄Mn ₂Ba₈ and Ge₄₂Mn₄Ba₈ clathrates

We calculate the electronic structures and magnetism of the germanium clathrate Ge₄₄Mn₂Ba₈ and obtain a magnetic moment of 0.77μ_B per manganese atom, which agrees very well with the experimental result. Further calculations for the Ge₄₂Mn ₄Ba₈ clathrate predict a much higher moment of 2.56μ_B. Detailed analysis of the electronic structures for both cases indicates that magnetism comes solely from the Mn sites and the increased local moment in Ge₄₂Mn₄Ba₈ is due to stronger interaction between Mn atoms.