Electronic structure, chemical bonding, and spin polarization in ferromagnetic MnAl

The electronic structure of ferromagnetic τ-MnAl has been calculated using density-functional techniques (TB-LMTO-ASA, FLAPW) and quantum-chemically analyzed by means of the crystal orbital Hamilton population tool. While all observable quantities are in good agreement with experiment, the tetragonal structure of ferromagnetic MnAl is interpreted to arise from a nonmagnetic cubic structure by two subsequent steps, namely (a) an electronic distortion due to spin polarization followed by (b) a structural distortion into the tetragonal system. The various strengths of interatomic bonding have been calculated in order to elucidate the competition between electronic and structural distortion.