Magnetism of chalcopyrite semiconductors: Cd_{1 − x} Mn_x GeP₂

The recently reported room-temperature ferromagnetism in Cd_{1 − x} Mn_x GeP₂ was investigated for x = 1.0, 0.5, and 0.25 by the local density first-principles full-potential linearized augmented plane wave (FLAPW) and DMOL³ methods within both local-density approximation (LDA) and generalized gradient approximation (GGA). We find that the total energy of the antiferromagnetic (AFM) state is lower than the corresponding ferromagnetic (FM) state for all x studied. The GGA gives a better description of magnetic properties than LDA mainly due to its better prediction of structure, particularly for high Mn concentrations. The total spin moment of Cd_{1 − x} Mn_x GeP₂ is ∼5.0μ_B per Mn atom. The FM alignment between Mn and P increases the total energy of the Mn-Mn FM coupling and makes the AFM ordering preferable.