We distill from first-principles spin-polarized total-energy calculations some practical rules for predicting the magnetic state (ferromagnetic/antiferromagnetic/paramagnetic) of substitutional transition-metal impurity with different charge state in various host crystal groups Ⅳ, Ⅲ-Ⅴ, Ⅱ-Ⅵ, Ⅰ-Ⅲ-Ⅵ2, and Ⅱ-Ⅳ-Ⅴ2 semiconductors. The basic mechanism is the stabilization of a ferromagnetic bond between two transition metals if the interacting orbitals are partially-occupied. These rules are then subjected to quantitative tests, which substantiate the mechanism of ferromagnetism in these systems.We discuss cases where current electronic structure calculations agree with these rules, and identify a few cases where conflicts exist. The effect of doping on transition-metal magnetic properties is also covered by these rules by considering the oxidation state changes due to doping. In addition, we systematically apply these rules to ideal substitutional impurities, contrasting our predictions with experiment. Discrepancies may be used to assess the role of various nonidealities such as presence of additional dopants, precipitates, clusters, or interstitial sites.

The wider-gap members of a semiconductor series such as diamond→Si→Ge or AlN→GaN→InN often cannot be doped n-type at equilibrium. We study theoretically if this is the case in the chalcopyrite family CuGaSe2→CuInSe2, finding that: (i) Bulk CuInSe2 (CIS, Eg=1.04 eV) can be doped at equilibrium n-type either by Cd or Cl, but bulk CuGaSe2 (CGS, Eg=1.68 eV) cannot; (ii) result (i) is primarily because the Cu-vacancy pins the Fermi level in CGS farther below the conduction band minimum than it does in CIS, as explained by the “doping limit rule; (iii) Cd doping is better than Cl doping, in that CdCu yields in CIS a higher net donor concentration than ClSe; and (iv) in general, the system shows massive compensation of acceptors (CdⅢ,VCu) and donors (ClSe,CdCu, InCud).

Recently reported room-temperature ferromagnetic（FM）semiconductors Cd1-xMnxGeP2 and Zn1-xMnxGeP2 point to a possible important role of Ⅱ-Ⅳ-Ⅴ2 chalcopyrite semiconductors in “spintronic” studies. Here, structural, electronic, and magnetic properties of （i） Mn-doped II-Ge-VI2 (Ⅱ= Zn or Cd and V=P or As）chalcopyrites and（ii）the role of S as impurity in Cd1-xMnxGeP2 are studied by first-principles density functional calculations. We find that the total energy of the antiferromagnetic（AFM）state is lower than the corresponding FM state for all systems with Mn composition x=0.25, 0.50, and 1.0. This prediction is in agreement with a recent experimental finding that Zn1-xMnxGeP2 experiences a FM to AFM transition for T less than 47 K. Furthermore, a possible transition to the half-metallic FM phase is predicted in Cd1-xMnxGeP2 due to the electrons introduced by n-type S doping, which indicates the importance of carriers for FM coupling in magnetic semiconductors. As expected, the total magnetic moment for the FM phase is reduced by one mB with each S substituting P.

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.

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.