Ferromagnetism in Ⅰ-Ⅲ-Ⅵ2 chalcopyrite semiconductors is predicted to arise from holes provided by Mn doping in the illustrative case of CuGaSe2. The first-princi plescalculations within the generalized gradientapproximation to density functional theory demonstrate that Mn substitutes for Ga sites in CuGaSe2 with a formation energy that is～0.25 eV lower than that for Cu sites. Ferromagnetic CuGa1-xMnxSe2 is found to be a half-metallic material with a magnetic moment of 4 µB per Mn for x≥0.25, and its estimated Curie temperature is more than 110 K. We suggest that higher Curie temperatures may be achieved for this new class of ferromagnetic semiconductors based on Mn-doped Ⅰ-Ⅲ-Ⅵ2 chalcopyrites by employing other materials with a smaller lattice constant such as CuGaSe2 and CuAlSe2.

Ga1-xMnxAs and related semiconductors are under intense investigation for the purpose of understandingthe ferromagnetism in these materials, pursuing higher TC, and, finally, for realizing semiconductor electronic devices that use both charge and spin. In this work, the electronic and magnetic structures of Ga1-xMnxAs (x＝3.125%, 6.25%, 12.5%, 25.0%, 50.0%） are studied by first-principles full-potential linearized augmented plane wave calculations with the generalized-gradient approximation. The ferromagnetic state is lower in energy than the paramagnetic and antiferromagnetic states. It is confirmed that Mn atoms stay magnetic with well localized magnetic moments. The calculated band structure shows that Mn doping also forms defect bands, and makes（Ga,Mn）As p-type conducting by providing holes. Furthermore, an s-d population inversion is found in the Mn electronic configuration, which results from the strong Mn p-d mixing. The induced As moments are substantial（about 20.15µB per Mn atom, and almost independent of x)—in accord with a recent observed negative As magnetic circular dichroism signal.

The recently reported room-temperature ferromagnetism in Cd1-xMnxGeP2 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 Cd1-xMnxGeP2 is～5.0µB per Mn atom. The FM alignment between Mn and Pincreases the total energy of the Mn-Mn FM coupling and makes the AFM ordering preferable.

The quest for combining semiconducting with ferromagnetic properties has recently led to the exploration of Mn substitutions not only in binary (GaAs, CdTe), but also in ternary semiconductors such as chalcopyrites ABⅢX2Ⅵ. Here, however, Mn would substitute any of the two metal sites A or B. The site preference of Mn doping in CuMⅢX2Ⅵ chalcopyrite is crucial because it releases different type of carriers: electrons for substitution on the Cu sites, and holes for substitution on the MⅢ sites. Using first-principles calculation we show that Mn prefers the MⅢ site under Cu-rich and Ⅲ-poor conditions, and the Cu site under Ⅲ-rich condition. We establish the chemical potential domains for pure CuAlS2, CuGaS2, CuInS2, CuGaSe2, and CuGaTe2 stability. We show that the solubility of Mn on the MⅢ (Cu) site increases (decreases) as the Fermi level moves toward the conduction-band minimum (n-type conditions). It is further found that domains of chemical stability of all these chalcopyrites may be largely reduced by Mn incorporation.

We report density-functional calculations of the ferromagnetic (FM) stabilization energy δ=EFM-EAFM for differently oriented Mn pairs in Ⅲ-V's (GaN, GaP, GaAs) and chalcopyrite (CuGaS2, CuGaSe2, CuGaTe2) semiconductors. Ferromagnetism is found to be the universal ground state (δ＜0) in all cases. The order of FM stability in Ⅲ–V’s is GaN＞GaP＞GaAs, whereas in chalcopyrites it is CuGaS2＞CuGaSe2＞CuGaTe2. Considering both groups, the order is GaN →GaP→GaAs→CuGaS2→CuGaSe2→GaSb≈CuGaTe2. The stronger FM stabilization in Ⅲ-V's is attributed to the stronger covalent coupling between the Mn 3d and the anion p orbitals. In contrast to expectations based on Ruderman-Kittel-(Kasuya)-Yosida, (i)all Mn-Mn pair separations show FM, with no FM to antiferromagnetic oscillations and, (ii) FM is orientationally dependent, with <110> Mn-Mn pairs being the most FM.