The coloring and magnetic structures of tetragonal Cu2Sb-type di-metal arsenides (MM'As; M, M� = Cr, Mn, Fe) were examined using density functional calculations. MM'As has two distinct sites for transition metals: (M) tetrahedrally coordinated by As forming planar square nets; and (M') square pyramidally coordinated by As forming metal bilayers. Magnetic coupling plays a role in the coloring, e.g., in MnFeAs, Mn occupies the M' site only when spin-polarized calculations are applied.  The bonding characters of the metal-metal contacts near the Fermi level play an essential role in the different magnetic ordering patterns.  In particular, the magnetic ground state of Cr2As has antiferromagnetic Cr-Cr' coupling along the a-axis, but ferromagnetic coupling along the b-axis. Therefore, a tetragonal to orthorhombic distortion is predicted in Cr2As at low temperature.  Also, because of the relatively strong Cr'-Cr' next nearest neighbor ferromagnetic coupling, Cr2As has a larger c/a ratio than other di-metal arsenides.

First-principles calculations of coloring and magnetic order in di-metal arsenides

244th National Meeting (2012)

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