Semiconductor Magnetism
Diluted magnetic semiconductors
this family of material
magnetic impurities in semiconductors
we can describe the DMS according to the model in which the electron states can divided in to two categories:
(i) localized magnetic d or f shells (ii) extended band states built up of s, p, and some times d atomic orbitals
The starting point for developing a useful predictive model of (III-Mn)V ferromagnetism is understanding of the electronic state with the single Mn impurity in the host lattice. we need to understand the charecter of Mn local moments before we explein how these isolated local moments are coupled. Ao we discuss the property of Mn impurity in GaAs and on the nature of ferromagnetic coupling in (Ga, Mn)As.
Between (III,V) hosts, Mn impurity has been studied in GaAs. The elements in the (Ga,Mn)As compound have nominal atomic structures:
[Ar]3d10 4s2 p1 for Ga
[Ar]3d5 4s2 for Mn
[Ar]3d10 4s2 p3 for As
This circumstance correctly suggests that the most stable and therefore most common position of Mn in the GaAs host lattice is on the Ga site where its two 4s electrons can participate in crystal bonding in much the same way as the two Ga 4s electrons. The substitutional MnGa , and the less com- mon interstitial MnI , positions are illustrated in Fig. 1. The MnGa impurity can be as an acceptor Because of the missing valence 4p electron. In the electrically neutral state, labeled as A0 (d5 + hole), MnGa has the character of a local moment with zero angular momentum and spin S = 5/2 and a moderately bound hole.Since The local moment is formed by three occupied sp-d bonding states with dominant (3dxy , 3dxz , 3dyz) character and by two occupied
orbitals that are split from the sp-d states by the tetrahe-orientation and together comprise the S = 5/2 local mo-
ment. The weakly bound hole occupies one of the three
antibonding sp-d levels with dominant As 4p character.
The charge
−e ionized MnGa acceptor center, labeled as
A−(d5 ), has just the S = 5/2 local spin character.
