Abstract
The observed ground state for the CuMnSb alloy is the antiferromagnetic (111) phase as confirmed by neutron diffraction experiments. Ab initio total energy calculations for ideal, defect-free CuMnSb contradict this result and indicate that other magnetic structures can have their total energies lower.
It is known that Heusler alloys usually contain various defects depending on the sample preparation. We have therefore investigated magnetic phases of CuMnSb assuming the most common defects which exist in real experimental conditions.
The full-potential supercell approach and a Heisenberg model approach using the coherent potential approximation are adopted. The results of the total energy supercell calculations indicate that defects that bring Mn atoms close together promote the antiferromagnetic (111) structure already for a low critical defect concentrations (approximate to 3%).
A detailed study of exchange interactions between Mn moments further supports the above stabilization mechanism. Finally, the stability of the antiferromagnetic (111) order is enhanced by inclusion of electron correlations in narrow Mn bands.
The present refinement structure analysis of the neutron scattering experiment supports theoretical conclusions.